The 18th International Symposium on Origin of Matter and Evolution of Galaxies (OMEG18)

Oct 20, 2026, 9:00 AM → Oct 23, 2026, 5:30 PM Asia/Tokyo

Headquarters Building 2F (RIKEN)

Hidetoshi Yamaguchi (CNS, the University of Tokyo), Kenichi Yoshida (The University of Osaka), Masaaki Kimura (RIKEN Nishina Center), Mizuki Kurata-Nishimura (RIKEN), Shunji Nishimura (RIKEN Nishina Center), Tadaaki Isobe (RIKEN), Tomoya Naito (The University of Tokyo), Yutaka Watanabe (KEK)

[Important Announcement]

Please ignore any emails regarding the workshop from travel agencies or other companies that are not from the organizers or RIKEN, as we do not request accommodation support from any company.

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[Overview]

The 18th International Symposium on Origin of Matter and Evolution of Galaxies (OMEG18) will be held at RIKEN (Wako Campus), Japan, from October 20 to 23, 2026.

OMEG18 is the 18th symposium in a series that has been held almost every two years since 1988. The symposium aims to discuss topics related to nuclear astrophysics and its associated fields, bringing together researchers and students from a broad range of disciplines.

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[Topics]

Topics to be covered include:

• Big Bang cosmology and primordial nucleosynthesis
• First-generation stars and galactic chemical evolution
• Astronomical observations with light, X-ray, gamma-ray, and cosmic rays
• Stellar evolution and hydrostatic burning processes
• Nuclear matter and neutron stars
• Explosive stellar objects and nuclear physics
• Meteorite analysis and isotopic abundances
• Theoretical nuclear physics for astrophysics
• Experimental nuclear physics for astrophysics
• Nuclear data for astrophysics and related topics
• Underground nuclear astrophysics
• Next-generation RI beam facilities for nuclear astrophysics

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[Important Dates]

• March 2, 2026: First circular
• April 9, 2026: Second circular
• April 9, 2026: Abstract submission opens
• May 1, 2026: Registration opens
• June 28, 2026: Abstract submission deadline (Extended)
• July 21, 2026: Third circular
• July 31, 2026: Registration with visa document request deadline
• July 31, 2026: Notification of the abstract
• August 30, 2026: Early-bird payment deadline
• September 11, 2026: Final circular
• October 12, 2026: Registration deadline
• October 14, 2026: Payment deadline

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[Contacts]

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[Sponsors / Supports]

  　 

     

           

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[The past OMEG symposia]

• OMEG 17 (2024) ... Chendu, China
• OMEG 16 (2022) ... Hanoi, Vietnam
• OMEG 15 (2019) ... Kyoto, Japan
• OMEG 14 (2017) ... Daejeon, Korea
• OMEG 13 (2015) ... Beijing, China
• OMEG 12 (2013) ... Tsukuba, Japan
• OMEG 11 (2011) ... Wako, Japan
• OMEG 10 (2010) ... Osaka, Japan

OMEG18_2nd-circular.pdf

OMEG18_3rd-circular.pdf

Tue, October 20

9:00 AM → 9:50 AM Registration

9:50 AM → 11:20 AM Scientific Session: Session 1

9:50 AM Opening

Speaker: Shunji NISHIMURA (RIKEN)

10:00 AM Nuclear Physics of Accreting Neutron Stars

Accreting neutron stars show a broad range of nuclear physics driven observable phenomena. These include short and long X-ray bursts, superbusrts, possible hyper bursts, absorption features in spectra, and crustal cooling. I will review the open questions as well as the current status and prospects of understanding the underlying nuclear physics. In that context I will present some recent results from measurements at the FRIB radioactive beam facility at Michigan State University.

Speaker: Hendrik Schatz (Michigan State University)

10:25 AM Astrophysical searches for X-ray/gamma-rays from r-process nuclei of Galactic Neutron-Star Merger Remnants in Globular Clusters

Since the discovery of the kilonova GRB130603B (Tanvir et al. 2013) and the gravitational-wave event GW170817 (Villar et al. 2017), neutron-star mergers (NSMs) have been regarded as the leading candidates for the r-process nucleosynthesis site. Although MeV gamma rays from unstable r-process nuclei would provide direct evidence of the r-process site, their expected luminosities are very dim (Hotokezaka et al. 2016), falling below the sensitivities of current high-energy astronomical missions. An alternative strategy is to search for nearby Galactic NSMs using long-lived r-process nuclei (Terada et al. 2022), which can in turn constrain the local NSM event rate. However, the required sensitivity remains beyond the sensitivity of present and near-future gamma-ray missions. A more promising approach is to target internal-conversion X-rays (ICX) from r-process nuclei through high-resolution X-ray spectroscopy with the latest observatory, XRISM, focusing on multiple NSM remnants in globular clusters. In our presentation, we will show the detailed feasibility of X-ray observations and prospects.

Speaker: Prof. Yukikatsu Terada (Saitama Univ. / JAXA)

10:45 AM Constraining the Astrophysical Role of the 14O(α,p)17F Reaction in Type I X-ray Bursts

Type I X-ray bursts, one of the explosive astrophysical phenomena, provide important sites for nucleosynthesis. The 14O(α,p)17F reaction is a key breakout pathway from the hot CNO cycle and strongly influences the onset of the rapid proton-capture process. However, most available constraints rely on indirect measurements, and direct cross-section data in the low-energy regime relevant to X-ray bursts remain scarce, leading to significant uncertainties in astrophysical models.
We performed a direct measurement of the 14O(α,p)17F reaction using the active-target time projection chamber TexAT_v2 with a radioactive 14O beam from the CRIB. The measurement extends experimental constraints toward lower center-of-mass energies in the astrophysically relevant region. Reaction events were reconstructed using Micromegas tracking together with silicon and CsI(Tl) detectors, and analyzed with the LILAK framework, including Geant4-based efficiency simulations.
We will present the measured excitation function and compare the results with previous experiments and theoretical predictions. The implications of the updated cross-section constraints for the astrophysically relevant energy region and Type I X-ray burst models will be discussed.

Speaker: Chaeyeon Park (IRIS/IBS)

11:05 AM New clocked burster Cir X-1 as a probe of explosive hydrogen burning

Type I bursts are transient explosions triggered by the thermonuclear burning of the accreted matter accumulated on neutron star (NS) surfaces. Among Type I bursters, several sources exhibit bursts with nearly constant recurrence times ($t_{\rm rec}$), known as “clocked bursts”. Clocked bursters serve as useful probes for the nature of low-mass X-ray binaries (LMXBs)—including accretion rate, inferred from persistent flux ($F_{\rm per}$) and its compositions—as well as the properties of NSs, such as $rp$-process, mass, radius, and temperature.
We report the discovery of clocked bursts from Circinus X-1 (hereafter Cir X-1) observed in 2023. We identified 71 bursts in total with $t_{\rm rec}$ and $F_{\rm per}$ varying across different observational epochs. At lower fluxes below 0.6 times the Eddington limit ($F_{\rm Edd}$), $t_{\rm rec}$ exhibits a clear anti-correlation with $F_{\rm per}$, as seen in most bursters. In contrast, at higher fluxes ($F_{\rm per}$ ~ 0.65$F_{\rm Edd}$), $t_{\rm rec}$ dropped by approximately half without a corresponding change in $F_{\rm per}$. We attribute this shift in burst regimes to marginally stable burning—where a fraction of the fuels burn stably while the remainder triggers bursts—occurring during the luminous phases. Aside from Cir X-1, IGR J17480−2446 is the only source known to exhibit a continuous transition between stable and unstable burning, making Cir X-1 a crucial source for understanding nuclear burst regimes.
Burst durations ($\tau_{\rm D}$) strongly depend on the hydrogen fraction in burning fuel via the $rp$-process. We found that $\tau_{\rm D}$ of Cir X-1 is a few seconds longer than those of GS 1826−24, a well-known solar-abundance system, implying the hydrogen-rich environment in this binary. This conclusion is well consistent with the extremely young age of Cir X-1 (<4600 yr) suggested by a supernova remnant associated with this system, whereas most bursters typically classified as LMXBs are much older (~$10^9$ yr). This supports the scenario where the hydrogen envelope in such a young binary has not yet been stripped (Ishii et al. to be submitted).

Speaker: Nonoka Ishii (Department of physics, Kyoto University)

11:20 AM → 11:45 AM Coffee Break

11:45 AM → 12:40 PM Scientific Session: Session 2

11:45 AM Fine structure and hindrance in the 12C+12C fusion

Recent experimental data have demonstrated that the coupled-channels
approach significantly overestimates fusion cross sections at deep subbarrier
energies. This phenomenon, referred to as fusion hindrance,
was first identified in the 60Ni+89Y system, and has subsequently been observed
in several other medium-heavy systems, such as 64Ni+64Ni. However, it remains
unclear to what extent fusion hindrance occurs in lighter systems, such as 12C+12C,
which are of critical importance to nuclear astrophysics.

In this contribution, I will present our recent reanalysis of fusion cross sections for
the 12C+12,13C systems and discuss the presence or absence of the fusion hindrance
phenomenon in these systems. I will also present our recent attempts to describe
fusion cross sections of these systems by combining a reaction model with shell model
calculations for the compound nuclei, 24,25Mg.

Speaker: Kouichi Hagino (Department of Physics, Kyoto University)

12:10 PM From Heavy Elements to Actinides: Constraining the Role of the i-Process at Low Metallicities

The intermediate neutron-capture process (i-process) has emerged as one of the most promising yet least understood nucleosynthetic mechanisms responsible for the production of heavy elements beyond iron. Operating at neutron densities intermediate between those of the slow (s-) and rapid (r-) neutron-capture processes (~10¹³–10¹⁵ cm⁻³), the i-process is capable of producing distinctive abundance signatures that cannot be explained by the classical s- or r-process alone. Although theoretical models predict that the i-process may occur during proton-ingestion episodes in evolved stars, its astrophysical site, operating conditions, and contribution to Galactic chemical evolution remain uncertain. Carbon-Enhanced Metal-Poor (CEMP) stars exhibiting simultaneous enhancements of s- and r-process elements (the so-called CEMP-rs stars) provide one of the most compelling observational laboratories for investigating i-process nucleosynthesis, as their heavy-element abundance patterns closely resemble theoretical i-process predictions. In our recent study (A. M. Riyas et al. (2026)), we investigated the presence of very heavy neutron-capture elements, including the actinides, in a sample of CEMP stars using high-resolution, high signal-to-noise near-ultraviolet spectra obtained with UVES on the VLT. We successfully determined the abundances of very heavy r-process elements such as Tb, Ho, Tm, Yb, Os, Ir, and Ta, in approximately seventeen stars and detected actinides in three of them. The key result of this work is the detection of actinides in three CEMP-rs stars, representing the first observational evidence for the presence of actinides in confirmed CEMP-rs stars. The observed abundance patterns are in good agreement with theoretical i-process nucleosynthesis predictions, indicating that the i-process can make a significant contribution to the production of very heavy and actinide elements in CEMP-rs stars. These findings provide important new observational constraints on the operation of the i-process at low metallicities and offer valuable insights into the nucleosynthetic origin of heavy elements in the early Universe.

Speaker: Muhammed Riyas A (University of Calicut, Kerala, India)

12:25 PM Probing the N=126 Region: Decay Properties of Relevance to the r-Process

Unlocking the origins of the third r-process peak requires a broader understanding of the neutron-rich nuclei near the N=126 shell closure. To validate theoretical predictions and improve r-process calculations, new experimental data on these exotic isotopes are critical. This talk reports on measurements of half-lives and β-delayed neutron emission probabilities ($P_n$) for neutron-rich nuclei across the N=126 shell closure, performed during the BRIKEN campaign at RIBF, including the first measurements of 40 isotopes. The implications on nuclear structure and impact on nucleosynthesis will be discussed.

Speaker: Tik Tsun Yeung (The University of Tokyo)

12:40 PM → 2:00 PM Lunch and Coffee

2:00 PM → 3:50 PM Scientific Session: Session 3

2:00 PM COLLECTIVE NEUTRINO OSCILLATIONS IN NUCLEAR ASTROPHYSICS

Collective oscillations of neutrinos represent emergent nonlinear flavor evolution phenomena instigated by neutrino-neutrino interactions in astrophysical environments with sufficiently high neutrino densities. These many-body systems exhibit interesting properties such as quantum entanglement. In this talk efforts to calculate evolution of the many-neutrino systems beyond the mean-field approximation, using both classical and quantum computing, will be discussed. Imprint of neutrinos on element formation in core-collapse supernovae and neutron star mergers will be illustrated.

Speaker: Baha Balantekin (University of Wisconsin, Madison)

2:25 PM A new Big Bang Nucleosynthesis measurement of the D+D reactions at CRYRING@FAIR

Big Bang Nucleosynthesis (BBN) models combine cosmological and particle physics models with nuclear reaction cross section data to predict the primordial abundances of the light elements. The deuterium abundance is of particular focus as it is extremely sensitive to the baryon density in the early Universe. A precise measure of the baryon density from BBN, along with precision measurements of the Cosmic Microwave Background (CMB), and the primordial deuterium abundance could provide for a probe of beyond the standard model physics between the BBN and recombination epochs in the early Universe. Astronomical observations of the primordial deuterium abundance and measurements of the CMB, have now reached percent level precision. However, the use of deuterium as a precision cosmological probe is now limited by uncertainties in the key D+D nuclear reaction cross sections.

In this talk, I will present a recent measurement of the D+D reactions using the CARME array at the CRYRING@FAIR low-energy storage ring. The CRYRING allows the storage of heavy-ions at low energies below 1 MeV/A, ideal for studying low-energy nuclear reactions for astrophysics. Here, deuterium ions were stored in the CRYRING at energies relevant for BBN and interacted with an ultra-thin gas-jet deuterium target every revolution around the ring. Nuclear reaction products were detected by specialised silicon detectors mounted directly under the extreme high-vacuum (XHV) conditions within the ring. I will present the details of this measurement and the potential impact on Big Bang Nucleosynthesis.

CARME is a significant part of the UK in-kind contribution to FAIR and is supported by the ERC-STG grant ELDAR.

Speaker: Jordan Marsh (The University of Edinburgh)

2:50 PM Big Bang Nucleosynthesis, Cosmic Entropy, Gravity, and the Cosmological Lithium Problem

Big Bang Nucleosynthesis, Cosmic Entropy, Gravity, and the Cosmological Lithium Problem

Big Bang Nucleosynthesis remains as a pillar of modern cosmology against which any modification of physics in the early universe must be constrained. This includes Einstein’s gravity and our understanding of the formation and evolution of stars in the early universe.. In this talk we will explore a concept rooted in AdS/CFT correspondence string theory and quantum entanglement, that gravity is an emergent phenomena and that entropy, not gravity, could be the underlying force driving the cosmic expansion as described in Kaniadakis cosmology. Existing BBN constraints will be reviewed and updated. At the same time, the cosmic lithium problem remains unsolved in spite of years of effort. We describe simple solutions to this based upon the detailed evolution of stars within the Spite plateau that has been used to quantify the primordial lithium abundance for decades.

Work Supported by the U.S. Department of Energy under Nuclear Theory Grant: DE-FG02-95-ER40934.

Speaker: Grant Mathews (University of Notre Dame)

3:10 PM Ending the second cosmological Li problem

Lithium is the heaviest element produced during Big Bang nucleosynthesis. The amount produced can be predicted through the cosmic microwave background and measured through old metal-poor stars. Li has two stable isotopes, with Li-7 being more abundant than Li-6. In particular, the detection of Li-6 in old metal-poor halo stars contradicts the Big Bang nucleosynthesis prediction by 5 orders of magnitude; this disagreement is known as the second cosmological lithium problem. We investigate the detections of Li-6 within three stars through the use of ESPRESSO@VLT observations and state-of-the-art synthetic spectra. We do not detect Li-6 in any star, indicating that there is no second cosmological lithium problem. This is consistent with Galactic modelling assuming Li destruction in old metal-poor stars.

Speaker: Ella Wang (Stockholm University)

3:30 PM The $^7$Be($n,p_1$)$^7$Li$^*$ reaction relevant to the cosmological lithium problem studied with the $^9$Be($^3$He,$\alpha$)$^8$Be($p$)$^7$Li and $^7$Li($^3$He,$d$)$^8$Be($p$)$^7$Li reactions

\documentclass[a4paper]{article}
\begin{document}
\begin{center}
\noindent The $^7$Be($n,p_1$)$^7$Li$^*$ reaction relevant to the cosmological lithium problem studied with the $^9$Be($^3$He,$\alpha$)$^8$Be($p$)$^7$Li and $^7$Li($^3$He,$d$)$^8$Be($p$)$^7$Li reactions\
\vspace{5mm}

N. Iwasa,$^1$ K. Ichimura,$^1$ S. Ishikawa,$^1$ S. Kubono,$^{2, 3}$ M. Egeta,$^1$ \
T. Haginouchi,$^1$ S. Ishio,$^1$, S. Matsue,$^1$ S. Numazawa,$^1$ K. Watanabe.$^1$ \
S. Sonoguchi,$^1$ T. Miyashita,$^1$ K. Nishio,$^4$ K. Hirose,$^4$ H. Makii,$^4$ \
R. Orlandi,$^4$ F. Suzaki,$^4$ J. Smallcombe,$^4$ S. Hayakawa,$^3$ and T. Kawabata$^5$
\
\vspace{5mm}
$^1${\it Department of Physics, Tohoku University, Sendai, Miyagi 980-8578, Japan.}\
$^2${\it RIKEN Nishina Center, RIKEN, Wako, Saitama 351-0198, Japan.}\
$^3${\it Center for Nuclear Study (CNS), the University of Tokyo,Wako, Saitama 351-0198, Japan}\
$^4${\it Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan.}\
$^5${\it Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan.}\
\end{center}

\noindent Abstract:

The primordial $^7$Li abundance observed in metal poor stars is known to be about one third of that predicted by the standard big bang nucleosynthesis (BBN) models.
This discrepancy is called ``the cosmological lithium problem'' and is one of the most important issues remained in BBN.
The questions are if (1) the BBN models correctly include all the nuclear reaction process,
(2) the astronomical observations correctly reflect the primordial $^7$Li abundance, or
(3) by other reasons like new physics beyond the standard model might be hidden.
From the point of the nuclear reaction process, since most of $^7$Li were immediately destroyed by the $^7$Li($p,\alpha$)$^4$He reaction,
the primordial $^7$Li was mainly synthesized by the electron capture of $^7$Be after the end of BBN epoch.
If the $^7$Be destruction reaction rate was large enough to reduce primordial $^7$Li abundance, then the present model would be validated without introducing any unknown physics.
The $^7$Be($n,p$)$^7$Li reaction is considered to be one of the most important $^7$Be destruction reactions.
However, the $^7$Be($n,p_1$)$^7$Li* (0.478keV, $\frac{1}{2}^-$) reaction was neglected in BBN except for the 2$^-$ state at 18.91 MeV in $^8$Be.

We have studied the $^7$Be($n,p_1$)$^7$Li$^*$ reaction by performing experiments to populate the resonant states at 18.9 - 20.1 MeV in $^8$Be by
the $^9$Be($^3$He,$\alpha$)$^8$Be$^*$ and $^7$Li($^3$He,$d$)$^8$Be$^*$ reactions and to measure decay protons to the ground and
first excited states in $^7$Li (called $p_0$ and $p_1$, respectively) [1].
The ($n,p_1$) contribution around BBN energy was found to be about 1 \%.
We are now studying $^7$Be destruction reactions by tritons by using transfer reactions.
The present status of the project will be also discussed.
\vspace{5mm}

\noindent
References: \
$[1]$ N. Iwasa {\it et al}., Phys. Rev. C{\bf 103}, 015801 (2021); N. Iwasa {\it et al}., Phys. Rev. C{\bf 112}, 035801 (2025).
\end{document}

Speaker: Naohito IWASA (Department of Physics, Tohoku University)

3:50 PM → 4:20 PM Coffee Break

4:20 PM → 6:10 PM Scientific Session: Sessin 4

4:20 PM Direct detection of interstellar radionuclides – messengers of heavy element nucleosynthesis and recent nearby cosmic explosions

Earth is exposed to nearby cosmic events. Freshly produced radionuclides in the interstellar medium contain information about how and where the heavy elements are made in nature. The solar system moves through the interstellar medium (ISM) and collects interstellar dust particles that contain fresh nucleosynthetic signatures, including the radionuclides Fe-60 (t${_{1/2}}$=2.6 Myr) and Pu-244 (t${_{1/2}}$=81 Myr) or Cm-247 (t${_{1/2}}$=15.7 Myr). These nuclides are incorporated into terrestrial archives over millions of years.
Detection of interstellar nuclides remains extremely challenging and so far was successful only with Accelerator Mass Spectrometry (AMS). Recent technical developments have seen an exceptional gain in measurement efficiency and sensitivity for smaller AMS systems, in particular for actinides, including Pu-244 and Cm-247; and more recently for Hf-182 (t${_{1/2}}$=9 Myr). On the other hand, very large accelerators with >10 million volts terminal voltage are required for the identification of small traces of interstellar Fe-60.
Recent data demonstrate a global Fe-60 influx and is evidence for exposure of Earth to recent (<10 Myr) supernova explosions. In addition, search in deep-sea archives and in lunar soil samples provides the first clear detection of interstellar Pu-244, an actinide nuclide exclusively produced by rapid-neutron capture (r-process), supporting the hypothesis that the dominant heavy element r-process nucleosynthesis is a rare process.
Besides new data for the direct search for interstellar signatures, including Fe-60, Pu-244 and the first search for Cm-247, I will also present preliminary results of recent laboratory measurements using AMS for understanding Fe-60 and Hf-182 production in massive stars - predominantly produced via double neutron capture reactions.

Speaker: Anton Wallner (FWIR-HZDR)

4:45 PM Direct Reaction and Resonance Studies for Nuclear Astrophysics at CENS

Nuclear physics inputs for rare isotopes remain one of the major sources of uncertainty in model predictions for astrophysical observables such as X-ray burst light curves, elemental abundance patterns, and stellar evolution. In particular, reaction rates involving short-lived nuclei and the resonance properties that govern them play an important role in explosive hydrogen and helium burning, breakout from the hot CNO cycle, and heavy-element nucleosynthesis. However, experimental information is still limited for many key reactions and states of astrophysical interest.

To address these questions, a broad experimental program in nuclear astrophysics has been pursued at the Center for Exotic Nuclear Studies (CENS) based on both direct and indirect approaches. Recent efforts include direct studies of astrophysically important ($\alpha$,$p$) reactions with active-target techniques, resonance and scattering studies relevant to reaction-rate constraints and nuclear structure, and detector developments for experiments with rare-isotope beams.

Representative topics include studies related to $^{14}\mathrm{O}(\alpha,p)^{17}\mathrm{F}$, $^{17}\mathrm{F}(\alpha,p)^{20}\mathrm{Ne}$ and $^{34}\mathrm{Ar}(\alpha,p)^{37}\mathrm{K}$, proton upscattering of the Hoyle state, optical-model-potential studies near the Coulomb barrier, and the development of the AToM-X active-target TPC. These activities are also establishing a practical path toward a sustained rare-isotope-beam nuclear astrophysics program at RAON.

Recent progress in direct reaction and resonance studies for nuclear astrophysics at CENS, selected research highlights, and future opportunities at RAON and other facilities will be presented.

Speaker: Sunghoon (Tony) Ahn (Institute for Basic Science)

5:10 PM First mass measurements of short-lived nuclei at HIAF-SRing

The HIAF project completed technical construction by the end of 2025, and started beam commissioning of the complex thereafter.

In April 2026, high-precision mass measurements of short-lived rare isotopes produced via projectile fragmentation of a $^{209}$Bi beam were successfully conducted with the storage ring SRing and in-flight separator HIRIBL, employing Isochronous Mass Spectrometry, as the first scientific experiment at HIAF.

This mass-measurement campaign aims at neutron-deficient nuclei in the vicinity of $N=82$. Nuclei in this region have long been of great interest because of the robustness of the N=82 shell gap. In this presentation, I will give a general introduction to the experiment, including the experimental setup, preliminary results, and ongoing analysis, as well as future plans for mass measurements of the neutron-deficient nuclei beyond $N=Z$ and the neutron-rich nuclei along $N=126$ at HIAF, which are motivated by the study of the $rp$-process and the $r$-process.

Speaker: Chaoyi FU (Institute of Modern Physics, Chinese Academy of Sciences)

5:30 PM Nuclear spectroscopy at KISS/KISS-1.5 to explore the origin of heavy elements synthesized by r-process

The KEK Wako Nuclear Science Center (WNSC) has developed the KEK Isotope　Separation System (KISS) at RIKEN to study the nuclear properties such as half-lives and atomic masses of the nuclei in the vicinity of neutron magic number N = 126, trans-uranium elements, and actinides. This research aims to explore the origin of heavy elements synthesized by the rapid neutron capture process.
The multinucleon transfer (MNT) reactions combined with a gas cell system enable us to produce these nuclei, which are difficult to study in other facilities. At the KISS facility, these neutron-rich nuclei have been produced by MNT reactions of 136Xe/238U beams and the production targets of W, Ir, and Pt. Their nuclear spectroscopy, including decay studies at a beta-gamma decay station, precise mass measurements using MRTOF-MS, and laser spectroscopy have been successfully performed.
To further this research, WNSC have started the construction of KISS-1.5 drastically to increase the experimental efficacy for nuclear spectroscopy.
In the talk, we will introduce the KISS facility, report the recent experimental results, and discuss future perspectives at KISS-1.5.

Speaker: Yoshikazu HIRAYAMA (IPNS, KEK)

5:50 PM Direct mass measurements for nuclear astrophysics and prospects toward the $N = 126$ r-process region

Nuclear masses of unstable nuclei are essential inputs for understanding nuclear structure far from stability and astrophysical nucleosynthesis. For neutron-rich nuclei, neutron separation energies are among the key nuclear inputs that shape the r-process path and element abundance peaks. However, experimental data remain limited for heavy neutron-rich isotopes relevant to the r-process. At RIKEN RIBF, the recent development of a high-intensity $^{208}$Pb primary beam, together with BigRIPS and ZeroDegree Spectrometer, has opened new opportunities to access heavy exotic nuclei near the predicted r-process path$^{[1]}$.
For astrophysical applications, mass uncertainties of <100 keV are often required to constrain separation energies and nucleosynthesis calculations. To achieve this precision, short-lived RIs are produced and separated by BigRIPS and ZeroDegree Spectrometer, stopped and extracted with a radio-frequency carpet-type helium gas cell, cooled in an ion trap, and injected into a multi-reflection time-of-flight mass spectrograph. With a measurement time of a few tens of milliseconds and relative mass precision of $\delta m/m < 10^{-7}$, MRTOF mass spectrometry is well suited for direct mass measurements$^{[2]}$.
In this contribution, we summarize recent mass measurements performed at RIBF. The results will be discussed in terms of separation-energy systematics, shell evolution$^{[3-6]}$, and implications for explosive nucleosynthesis$^{[7]}$. We will also present plans to extend MRTOF mass measurements toward neutron-rich nuclei around $N = 126$, enabled by recent heavy-RI beam developments at RIBF, and discuss challenges toward the third r-process abundance peak around $A = 195$.
[1] N. Fukuda $\textit{et al.}$, Prog. Theor. Exp. Phys. $\textbf{2026}$, 061D01 (2026).
[2] M. Rosenbusch $\textit{et al.}$, Nucl. Instrum. Methods Phys. Res. A $\textbf{1047}$, 167824 (2023).
[3] S. Iimura $\textit{et al.}$, Phys. Rev. Lett. $\textbf{130}$, 012501 (2023).
[4] D. S. Hou $\textit{et al.}$, Phys. Rev. C $\textbf{108}$, 054312 (2023).
[5] W. Xian $\textit{et al.}$, Phys. Rev. C $\textbf{109}$, 035804 (2024).
[6] W. Xian $\textit{et al.}$, Front. Phys. $\textbf{13}$, 1644477 (2025).
[7] S. Kimura $\textit{et al.}$, Phys. Rev. Lett. $\textbf{135}$, 152701 (2025).

Speaker: Shun Iimura

Wed, October 21

9:00 AM → 9:30 AM Morning Coffee

9:30 AM → 11:15 AM Scientific Session: Session 5

9:30 AM Modeling and nucleosynthesis of novae and X-ray bursts

Novae and X-Ray Bursts are among the most important stellar explosions in our Galaxy. Classical novae are driven by thermonuclear explosions in the envelopes accumulated through mass transfer onto white dwarf stars in close binary systems. During these events, approximately $10^{-7}-10^{-4}$ M$_\odot$ of material enriched in CNO nuclei, and in some cases in intermediate-mass elements such as Ne, Na, Mg, and Al, are ejected into the interstellar medium. Infrared and ultraviolet observations have also confirmed dust formation in the expanding nova ejecta, raising the possibility that novae may contribute to the inventory of presolar grains found in meteorites. Recent work on the subclass of recurrent novae, including T CrB and other well-known systems, has focused on characterizing their accretion histories and white-dwarf masses. In many recurrent novae, the accreting white dwarf is inferred to be close to the Chandrasekhar mass because of the observed short recurrence periods. Numerical simulations suggest that such systems may experience net white-dwarf mass growth, making at least some recurrent novae plausible progenitors of thermonuclear supernovae.

X-ray bursts (XRBs) are another class of thermonuclear explosions that involve neutron stars rather than white dwarfs. These events constitute the most frequent type of thermonuclear stellar explosion in our Galaxy (the third, in terms of total energy output after novae and supernovae). To date, most of the efforts undertaken in the modeling of XRBs have relied on non-rotating, 1D hydrodynamic simulations. We will report on pioneering XRB models computed with different angular velocities (up to 80% of the critical value) and discuss the differences obtained in the lightcurves and in the associated nucleosynthesis with respect to non-rotating models. It is worth noting that, while all XRB hydro simulations performed to date report that ejection from a neutron star is unlikely, radiation-driven winds during photospheric radius expansion have been suggested to lead to the ejection of a tiny fraction of the accreted envelope. Here, we will report the results of the coupling of a non-relativistic, radiative wind model with a series of XRB hydrodynamic simulations, quantifying the expected contribution of XRBs to the Galactic abundances.

This invited talk will review the current understanding of novae and XRB, with empasis on the explosion mechanisms, the main nuclear processes involved and their associated uncertainties. Particular attention will be devoted to the impact of nuclear reaction rates and weak interactions on abundance predictions and observational diagnostics.

Speaker: Jordi Jose (UPC Barcelona)

9:55 AM The 2025 evaluation of experimental thermonuclear reaction rates (ETR25)

Thermonuclear reaction rates are essential inputs for predictive models of stellar structure, evolution, explosions, and nucleosynthesis. In this talk, I will present a new evaluation of experimentally based thermonuclear rates for 78 proton- and alpha-induced reactions on target nuclei in the A<40 mass region. Building on earlier Monte-Carlo reaction-rate methods, the new evaluation applies modern statistical techniques, including Bayesian inference and Monte-Carlo sampling, to derive recommended rates and uncertainties with well-defined probabilistic meaning. The analysis incorporates experimental resonance strengths, indirect constraints on partial widths, nonresonant radiative-capture contributions, and high-temperature extrapolations where needed. For each reaction, rates are tabulated from 1 MK to 10 GK, together with fractional rate contributions and uncertainty estimates. The resulting laboratory-based rates provide a transparent and reproducible resource for uncertainty studies in nuclear astrophysics, while also highlighting where future measurements are needed to further improve stellar model predictions.

Speaker: Christian Iliadis

10:20 AM New s-process nucleosynthesis predictions for low-mass AGB stars and implications for meteoric data

We present new slow neutron-capture (s) process nucleosynthesis predictions calculated with the Monash post-processing code for low-mass asymptotic giant branch (AGB) stars of solar metallicity, half-solar, and double-solar metallicity. We updated many of the nuclear inputs related to decay and neutron-capture rates and will present several significant results related to presolar stardust grain and other meteoritic data. The new models quantitatively reproduce the minor s-process production of the classical p-only $\mathrm{^{94}Mo}$ observed in stardust silicon carbide (SiC) grains and match the $\mathrm{^{64}Ni}/\mathrm{^{58}Ni}$ values from the SiC grain data. Also, the $\mathrm{^{80}Kr}/\mathrm{^{82}Kr}$ and $\mathrm{^{137}Ba}/\mathrm{^{136}Ba}$ ratios are better fitted to SiC grains than using the previous models, while $\mathrm{^{138}Ba}/\mathrm{^{136}Ba}$ still presents some problems. Our new models still do not match the isotopic composition of W in large SiC stardust grains but do match the W composition observed in other types of meteoritic materials, especially when including the contribution of the long-lived $\mathrm{^{182}Hf}$ to $\mathrm{^{182}W}$. Finally, the first experimental measurement of the $\mathrm{^{205}Tl}$ decay rate in stars allowed us for the first time to use the radioactive s-process isotope $\mathrm{^{205}Pb}$ to determine the isolation time of solar material inside its parent molecular cloud. We obtain positive isolation times of around 10 Myr, consistent with those from $\mathrm{^{107}Pd}$ and $\mathrm{^{182}Hf}$, the other s-process short-lived radionuclides found in the early Solar System.

Speaker: Balázs Szányi (Konkoly Observatory)

10:40 AM Indirect measurements with stable beams to improve reaction rate calculations for explosive nucleosynthesis

The iThemba Laboratory for Accelerator-Based Science (LABS) in Cape Town, South Africa, is a leading facility in Africa with regard to experimental nuclear physics as well as radioisotope production. The lab hosts various accelerators, with one such instrument being the K=200 separated-sector cyclotron (SSC). The K=600 magnetic spectrometer, one of the SSC end stations, coupled with its ancillary detectors for singles and coincidence measurements, has been used in various studies relevant to nuclear astrophysics, among others. The K600 is a high-resolution magnetic spectrometer that uses dispersion matching with a drift-chamber focal plane and that can operate at 0°. One of only 2 spectrometers globally that can operate with these parameters. With silicon arrays for particle detection and lanthanum-bromide or clover arrays for gamma spectroscopy, this end station has proven to be a powerful and versatile instrument.

In particular, reaction rates relevant to type-I x-ray bursts (XRBs) and explosive nucleosynthesis in general have been measured. The hot CNO breakout reaction rate of $^{18}$Ne$(\alpha,p)$$^{21}$Na has been studied via the indirect $^{24}$Mg$(p,t)$$^{22}$Mg reaction, and $^{50}$Cr$(p,t)$$^{48}$Cr to determine the $^{44}$Ti$(\alpha,p)$$^{47}$V reaction rate. Measurements with approved beamtime include $^{28}$Si$(p,t)$$^{26}$Si for an indirect measurement of the $^{22}$Mg$(\alpha,p)$$^{25}$Al reaction rate and the $^{32}$S$(p,t)$$^{30}$S measurement, which will be used to measure astrophysically relevant states in $^{30}$S, to determine branching ratios for the $^{26}$Si$(\alpha,p)$$^{29}$P and $^{29}$P$(p,\gamma)$$^{30}$S reaction rates. This talk will discuss the research within the field of nuclear astrophysics that is conducted with the K600 magnetic spectrometer at iThemba LABS in South Africa.

Speaker: Johann Wiggert Brummer (iThemba LABS)

11:00 AM The Impact of the New 59Fe Decay Rates on 60Fe and 26Al Nucleosynthesis in Massive Stars

The diffuse $\gamma$-ray emission from short-lived radioactive $^{26}\text{Al}$ and $^{60}\text{Fe}$ provides a direct probe of ongoing nucleosynthesis in the Galaxy. However, theoretical models have long struggled to reproduce the observed $^{60}\text{Fe}/^{26}\text{Al}$ flux ratio, typically predicting values significantly higher than the constraints derived from INTEGRAL/SPI observations. In this work, we investigate the impact of the recently measured temperature-dependent stellar $\beta^-$ decay rate of $^{59}\text{Fe}$ on the nucleosynthesis of these isotopes. We compute a grid of nonrotating massive star models (14–80 $M_\odot$) at solar metallicity using the MESA code, coupled with a rigorous numerical resolution analysis. We find that the updated rate significantly suppresses the net production of $^{60}\text{Fe}$ by approximately 0.28 dex ($\sim 47\%$) compared to models using LMP theoretical rates, while leaving the $^{26}\text{Al}$ yields virtually unchanged. This reduction is primarily driven by the enhanced $\beta^-$ decay during convective carbon-shell burning. Integrating these yields over a standard Salpeter initial mass function (IMF), we predict a Galactic flux ratio of $\sim 0.18$, which is in excellent agreement with the observed value of $0.184 \pm 0.042$. Furthermore, this ratio exhibits a weak dependence on the IMF slope. Our results indicate that the updated nuclear physics input significantly alleviates the longstanding $^{60}\text{Fe}$ overproduction problem, bringing theoretical predictions into much closer alignment with current Galactic observations.

Speaker: Bingyang Tan (National Astronomical Observatories, Chinese Academy of Sciences)

11:15 AM → 11:40 AM Coffee Break

11:40 AM → 12:40 PM Scientific Session: Session 6

11:40 AM Extra-galactic archaeology - elemental abundances of high-z galaxies

Extra-galactic archaeology - elemental abundances of high-z galaxies

The James Webb Space Telescope (JWST) is expected to find the first galaxies - those hosting metal-free stars. Surprisingly, though, galaxies with strong metal lines have been detected indicating unusual chemical composition (e.g. high N/O ratio). Nitrogen can be enhanced not only by asymptotic giant branch (AGB) stars but also Wolf-Rayet (WR) stars. I show galactic chemical evolution models that can naturally reproduce N emitters with intermittent star formation. Wolf-Rayet stars are expected to enhance Fluorine as well. With Atacama Large Millimeter/submillimeter Array (ALMA), we show two submillimeter galaxies, one at z=4.4 with a high F abundance, while another at z=6.0 with no F enhancement, which further supports the intermittent star formation in early Universe. Although these do not require changing the initial mass function (IMF), I will discuss how other elements (C and Ar) can be used to constrain the IMF and the first stars.

Speaker: Chiaki Kobayashi (University of Hertfordshire)

12:05 PM Potassium abundances in extremely metal-poor stars as a probe of the final phases of massive star evolution

Potassium (K; Z = 19) is an essential element for life and for the formation of rocky planets. Along with other odd-Z elements such as scandium (Sc) and vanadium (V), potassium is generally thought to be synthesized during the evolution of massive stars or at the moment of core-collapse supernova explosions. However, quantitative predictions of potasium yields in massive stars, as well as the relative contributions from hydrostatic and explosive nucleosyntehsis, remain uncertain.

We used the High-Dispersion Spectrograph (HDS) on the Subaru Telescope to determine potassium abundances in 18 extremely metal-poor stars ([Fe/H]=log(N_Fe/N_H) − log (N_Fe/N_H)_Sun<-3), whose surface chemical compositions likely reflect the yields of individual massive-star supernovae.

We detected weak potasium resonance lines at 766/769 nm in seven stars.For these stars, we find that the potassium-to-calcium ratios ([K/Ca]) are nearly constant, with a mean value of +0.11 dex and a very small scatter, below the level of observational uncertainties. In contrast, large star-to-star variations are observed in Na/Mg ratios. In this talk, I will discuss the implications of these chemical abundance trends for the origin and chemical evolution of potassium.

Speaker: Dr Miho Ishigaki (National Astronomical Observatory of Japan)

12:25 PM Unveiling the Origins of Newly Discovered Super Li-Rich Stars

Standard stellar evolution predicts severe lithium depletion in evolved stars; however, a rare subset of giants with lithium abundances exceeding meteoritic values, known as “super Li-rich” (SLR; A(Li) > 3.3) stars, defies this expectation and presents a major astrophysical puzzle. To understand this extreme enhancement, it is essential to distinguish internal production (e.g., a “lithium flash”) and external pollution (e.g., binary mass transfer or planet engulfment) for possible origins. Because Li abundance alone cannot reveal its origin, a comprehensive and precise elemental abundance pattern is essential. In this presentation, we report on our program to derive precise stellar parameters and elemental abundances for four newly confirmed SLRs from the LAMOST MRS catalogue, followed up with high-resolution spectroscopic observations using Subaru/HDS and Gemini-N/MAROON-X, covering 400–900 nm. The Li abundances of these stars range from A(Li) ~ 3.6 to 4.5. Our targets include one subgiant, two red giants, and one supergiant, all exhibiting saturated Li 670.8 nm lines and spanning sub-solar to very metal-poor ranges. From the two observations with approximately one month separation, we detect indications of variability in spectral features of two targets, as seen in their H-alpha, Li 670.8 nm, and Na D line profiles. We aim to investigate the common or unique feature of these targets, exploring potential correlations with their evolutionary status or formation scenarios. Our results are compared to previously discovered SLRs and one ultra-Li-rich star (A(Li) ~ 6.5), for which an archive spectrum of Subaru/HDS is analyzed. Updated findings from this project will be presented in detail.

Speaker: Bakuh Danang Setyo Budi (SOKENDAI/NAOJ)

12:40 PM → 1:55 PM Lunch and Coffee

1:55 PM → 3:45 PM Scientific Session: Session 7

1:55 PM Underground nuclear astrophysics JUNA experiments

The Jinping Underground experiment for Nuclear Astrophysics (JUNA) takes advantage of the ultra-low background of the CJPL to conduct experiments for directly studying crucial reactions at stellar energies in the evolution of stars. From 2020, JUNA commissioned an mA level high current accelerator based on an ECR source, as well as high efficiency BGO and 3He detectors. These combination enabled JUNA to perform direct measurements of key nuclear reactions in $ 10^{-13} \, \mathrm{b} $ sensitivity with the beam exposure of few hundreds of Coulomb, including $ {}^{25} \mathrm{Mg} \left( p, \gamma \right) {}^{26} \mathrm{Al} $, $ {}^{19} \mathrm{F} \left( p, \alpha \gamma \right) {}^{16} \mathrm{O} $, $ {}^{19} \mathrm{F} \left( p, \gamma \right) {}^{20} \mathrm{Ne} $, $ {}^{13} \mathrm{C} \left( \alpha, n \right) {}^{16} \mathrm{O} $, $ {}^{12} \mathrm{C} \left( \alpha, \gamma \right) {}^{16} \mathrm{O} $, and $ {}^{18} \mathrm{O} \left( \alpha, \gamma \right) {}^{20} \mathrm{Ne} $ with improved precision and closer to the Gamow window. These precise reaction rates provide valuable insights into the high precision astrophysics simulation. The highlights of JUNA experiments such as $ {}^{12} \mathrm{C} \left( \alpha, \gamma \right) {}^{16} \mathrm{O} $ will be presented.

Speaker: Weiping Liu (China Institute of Atomic Energy)

2:20 PM Experimental Challenges in Underground Nuclear Astrophysics Laboratories: Status and Future Perspectives Toward the LUNANOVA Project

The goal of nuclear astrophysics is to measure nuclear reaction cross sections of astrophysical interest and to determine reaction rates in order to improve our understanding of stellar evolution and the synthesis of the elements. At the typical temperatures of stellar interiors, the relevant energy region—the so-called Gamow window—is of the order of a few hundred keV, where nuclear cross sections are extremely small due to the strong suppression caused by the Coulomb barrier.

The LUNA (Laboratory for Underground Nuclear Astrophysics) Collaboration has demonstrated that, by performing experiments deep underground and by applying low-background techniques developed in astroparticle physics, it is possible to measure nuclear cross sections down to energies relevant for stellar nucleosynthesis.

This talk will provide an overview of the experimental techniques adopted in underground nuclear astrophysics and will present the most recent results and major achievements of the LUNA experiment. In addition to the scientific program of LUNA, the newly funded LUNANOVA project—supported by the ERC Synergy Grant —will be introduced.

Speaker: Alba Formicola (INFN Roma)

2:45 PM The 19F(p,g)20Ne measurement at LUNA

The $^{19}$F + p reactions play a key role in two main scenarios: on one hand the nucleosynthesis of heavy elements (A $\le$ 40) via CNO break out, as observed in ultra-iron-poor stars. On the other hand, a precise knowledge of the $^{19}$F + p reaction rates, which represent the main destruction channels of fluorine, is crucial to understand its puzzling galactic origin and abundance. Among these processes, the detection of the $^{19}$F(p,$\gamma$)$^{20}$Ne reaction has long been elusive, owing to inevitable background from, $\gamma$-ray emissions associated with the (p,$\alpha_{2,3,4}$) channels. This limitation became apparent in early measurements, whose validity has been called into question by two late studies. More recently, an underground measurement at JUNA reported resonance strength and branching ratios for the resonances at $E_\mathrm{cm}$ = 323 keV and
$E_\mathrm{cm}$ = 225 keV (this latter observed for the first time), leading to a reaction rate up to a factor 7 larger than literature.
In the present talk I will report on a new experimental campaign performed at LUNA, located at the underground Laboratori Nazionali del Gran Sasso (Italy) owing to a reduction of cosmic-ray background by several orders of magnitude. The high sensitivity setup exploited, measurement details and techniques and preliminary results for both $(p,\alpha\gamma)$ and $(p,\gamma)$ channels will be presented in the talk.
Finally, LUNA collaboration propose a series of experiments to tackle the $^{19}$F(p,$\alpha$)$^{16}$O reaction channels, for which poor data are available below 500 keV, exploiting a new detection system to detect simultaneously charged particles and $\gamma$ rays and a novel approach for the investigation of the (p,$\alpha_1$) reaction.

Speaker: Denise Piatti (INFN, Division of Padova)

3:05 PM Indirect Measurement of the 16O(12C,α)24Mg Reaction at Stellar Energies

The 16O(12C,α)24Mg reaction is one of the major channels of the 12C+16O fusion process and plays
an important role during the advanced evolution of massive stars (M>8M⊙), as well as during explosive
carbon and oxygen burning. The astrophysical energy region extends from 3 to 7.2 MeV in the center-of-mass frame.
Experimental investigations of the 16O(12C,α)24Mg reaction are currently limited to center-of-mass
energies above 4 MeV, making extrapolations to lower energies unavoidable. To investigate this unexplored
region, the 16O(12C,α)24Mg reaction has been studied by applying the Trojan Horse Method [1] to the
three-body reaction 16O(14N,α24Mg)2H, covering the entire astrophysical energy range.
The extracted astrophysical S(E)factor exhibits pronounced resonant structures below 4 MeV, enhancing the non-resonant extrapolation by about a factor of 200. These results provide the first experimental evidence that the low-energy behavior of the α channel is dominated by resonant contributions
rather than by a smooth non-resonant trend, with important consequences for the corresponding stellar
reaction rate. The experiment, the data analysis, and the obtained results will be presented and discussed.

[1] A. Tumino et al., Ann. Rev. Nucl. and Part. Phys. 71 (2021) 345

Speaker: Aurora Tumino (Dipartimento di Ingegneria e Architettura, Universita degli Studi di Enna “Kore”, Italy & INFN–LNS, Laboratori Nazionali del Sud, Catania, Italy)

3:25 PM Neutron induced reactions for BBN: the ^3He +n case

Nuclear reactions induced by neutrons play a key role in several astrophysical scenario like primordial nucleosynthesis, s and r process and so on. From an experimental point of view, their reaction cross sections and reaction rates at astrophysically relevant temperatures are usually a hard task to be measured directly. Nevertheless big efforts in the last decades have led to a better understanding of their role in the different nucleosynthetic networks. In this work we will review the possibility of application of the Trojan Horse Method to extract the cross section at astrophysical energies for neutron induced reactions, examining validity tests as well as different applications. Moreover a detailed study of the $^3$He(n,p)$^3$H reaction off the $^2$H($^3$He,pt)H three--body process will be discussed. The experiment was performed using the $^3$He beam, delivered at a total kinetic energy of 9 MeV by the Tandem at the Physics and Astronomy Department of the University of Notre Dame. Data extracted from the present measurement are compared with other published sets available in literature. the reaction rate will be calculated and the astrophysical applications will also be discussed in details for the case of the Big Bang Nucleosynthesis.

Speaker: rosario pizzone (infn lns)

3:45 PM → 4:15 PM Coffee Break

4:15 PM → 5:40 PM Scientific Session: Session 8

4:15 PM Chemical and isotopic analysis of samples returned by the Hayabusa2 mission from the asteroid Ryugu

Sample return missions are of vital importance to the scientific community, particularly in the domains of planetary science and cosmochemistry. These missions provide pristine, terrestrially unaltered extraterrestrial materials that can be analyzed in a laboratory with a level of detail that is not possible through remote sensing. The recent success of asteroid sample return missions has led to significant advancements in solar system science. The Hayabusa2 mission by JAXA successfully retrieved a total of 5.4 grams of samples from two locations on the surface of the C-type asteroid (162173) Ryugu and returned them back to Earth. A series of analyses for the elemental abundances of these samples indicated that Ryugu bear a strong resemblance to those of the Ivuna-type (CI) carbonaceous chondrites, which are a unique group of meteorites with a chemical composition similar to that of the solar photosphere except for highly volatile elements (noble gases, H, C, N, and O) and Li that was destroyed in the Sun by nuclear reactions. Additionally, the isotopic compositions in bulk Ryugu samples were generally consistent with those of CI chondrites, suggesting that the source materials of Ryugu and CIs share a common genetic heritage. Since the materials observed in CI chondrites may have been modified on Earth, the Ryugu samples are more chemically pristine than other Solar System materials that have been analyzed in laboratories, including CI chondrites. Thus, it is suggested that Ryugu is the most primordial material in the Solar System and serves as a crucial reference for studying the origin and evolution of the Solar System.

Speaker: Tetsuya Yokoyama (Department of Earth and Planetary Sciences, Institute of Science Tokyo)

4:40 PM Meteoritic isotopic anomalies as precision tests of stellar nucleosynthesis

Meteoritic isotopic anomalies preserve the isotopic fingerprints of stellar nucleosynthesis before and during Solar System formation. In presolar grains, these signatures can be measured in individual stellar condensates, while bulk meteorite components and leachates record the incomplete mixing of distinct nucleosynthetic carriers in the solar protoplanetary disk. Together, these materials provide some of the most precise laboratory constraints on neutron-capture nucleosynthesis, stellar evolution, and Galactic chemical evolution.
In this invited talk, I will give a broad introduction to meteoritic isotopic anomalies and discuss recent collaborative efforts to revisit several long-standing discrepancies between meteoritic data and asymptotic giant branch star (AGB) predictions. Using updated neutron-capture information from the n_TOF and Back-n facilities together with FRUITY AGB models, we found that several previously unresolved isotope systems can now be brought into good agreement with meteoritic constraints. These include Dy isotopic anomalies in meteorite leachates, Mo–Nb systematics relevant to 94Mo/92Mo in presolar SiC grains, and the 64Ni enrichments of AGB-derived SiC grains.
Although these cases all point toward improved agreement between meteoritic data and AGB nucleosynthesis, the underlying causes of the earlier discrepancies are different. For Dy isotopes, the mismatch was likely amplified by limitations in early meteoritic measurements, including unresolved isobaric interferences. For Ni isotopes in presolar SiC grains, earlier measurements were affected by solar Ni contamination, whereas new Ni isotope data reveal intrinsic AGB signatures consistent with FRUITY predictions when updated 64Ni neutron-capture constraints are used. For the Mo–Nb system, the key issue lies instead in the inaccurate treatment of the temperature-dependent β− decay rate of 94Nb in previous AGB models, which limited the production of 94Mo through the β− decay channel.
I will also discuss how the new Ni isotope measurements of presolar SiC grains extend beyond AGB nucleosynthesis. In particular, correlated 60Ni enrichments in selected grains provide isotopic evidence for local Type Ia supernova pollution of the parent molecular clouds from which their parent stars formed. These results show how meteoritic isotopic anomalies can be used not only to refine nuclear inputs and stellar models, but also to trace the evolving contributions of different stellar sources to Galactic chemical evolution.

Speaker: Nan Liu (Boston University)

5:05 PM The evidence of the supernova neutrino-process recorded in the oldest solids in the solar system

A huge number of neutrinos radiated at supernova explosions is considered to have an important role for production of some rare isotopes (ν-process). Although some measurements such as astronomical observation of 19F in metal poor stars and the existence of a short-lived radioisotope of 92Nb at the solar system formation in primitive meteorites are candidates for the ν-process, there is no clear evidence that the ν-process actually occurred in the universe. Our previous prediction has demonstrated that the correlation between the isotopic ratios at least in two different elements can constrain the astrophysical conditions where presolar grains were produced [1]. Here we present the result that a detailed core-collapse a supernova (CCSN) nucleosynthesis calculation including the ν-process reproduce the correlation between enhancement of 138La/139La and 50Ti/48Ti observed in calcium-aluminum-rich inclusions (CAIs) in primitive meteorites, which are the oldest solids in our solar system. In our calculation, 138La is predominantly produced from 138Ba by the charged current reactions with electron neutrinos, and 50Ti is produced by successive neutron capture reactions on Ti isotopes.
This result is consistent with the recent result that the isotopic abundance anomalies of Ti isotopes observed in CAIs can be only explained by the slow neutron capture reactions (s-process) in C-shell burning in massive star before the SN explosion [2]. The present result shows that the La-Ti correlation observed in the CAIs is the evidence that the ν-process in CCSNe occur in the universe, and that its product contributed to the early solar materials. This gives a hint to the long-standing problem whether the collapse of the proto-solar nebula was triggered by the shock by a nearby SN. We present the detailed nucleosynthesis calculation with key neutrino-nucleus reactions and the role of the s-process in C-shell burning. We also explain the model of the mixing of the SN ejecta to the proto-solar nebula.
[1] X. Yao, et al. ApJ, 980, 247 (2025).
[2] T. Iizuka, et al. ApJL, 979, L29 (2025).

Speaker: Takehito Hayakawa (National Institutes for Quantum Science and Technology)

5:25 PM Tracing Circumstellar Dust Formation and Evolution with Presolar Silicates in DOM 08006

Presolar grains are survivors of circumstellar dust preserved in primitive meteorites. They enable laboratory analyses of circumstellar dust formation and evolution [1]. Astronomical observations and circumstellar models suggest that circumstellar dust of oxygen-rich asymptotic giant branch (AGB) stars comprises diverse mineral phases, including predominantly amorphous, Mg-rich silicates, corundum, and metastable (transition or amorphous) alumina [2]. However, microstructural studies have shown that nearly half of presolar silicates characterized by TEM are crystalline, whereas the remaining amorphous grains exhibit a broad range of Mg/(Mg+Fe) ratios [3]. Similar discrepancies are also observed for Al-rich oxides, where circumstellar dust is inferred to contain corundum and metastable alumina, whereas presolar oxides are dominated by corundum and spinel [4]. These observations raise the possibility that the discrepancy between circumstellar silicate dust and presolar silicates may also reflect post-condensation dust evolution [5]. To investigate the relationship between the mineralogical and compositional diversity of presolar silicates and circumstellar dust evolution, we conducted coordinated isotopic and microstructural analyses of newly identified presolar silicates.

Smooth matrix areas, which are expected to contain abundant presolar grains [5], were selected from a thin section of Dominion Range (DOM) 08006 (CO3.0). Isotopic imaging of secondary ions (12C, 13C, 16O, 17O, 18O, 28Si, 27Al16O) was performed with a CAMECA NanoSIMS 50L (ARIM, U.Tokyo). We analyzed the oxygen isotope ratios per pixel (17O/16O, 18O/16O) and identified presolar grains using L'IMAGE software. Some of the identified presolar grains and surrounding matrix were extracted by FIB (Helios5 Dualbeam; TF), and (S)TEM analysis (JEM-2800, JEM 2100F; JEOL) was performed to determine the chemical compositions and the mineral phases.

We identified 79 presolar oxides and silicates (8 oxides and 71 silicates) from an area of ~19,670 μm². Five presolar silicates were further characterized by TEM. One grain (AREA06_20_Si_PG47) belongs to Group 3, indicating an origin in a low-mass, low-metallicity AGB star. This is the first in-situ TEM analysis of a Group 3 presolar silicate from a meteorite. The grain is a ~1400 nm single-crystalline olivine with Mg/(Mg+Fe) ~ 0.9. The remaining four grains belong to Group 1 (low- to intermediate-mass AGB stars): three are olivine with Mg/(Mg+Fe) > 0.7, whereas one (LCM01b_Si_PG07) is an amorphous, Ca-bearing Fe-rich grain with a composition of (Mg0.50Fe0.83Ca0.28)Al0.09SiO3.75.

The high fraction of crystalline grains among TEM-characterized presolar silicates in this study may reflect secondary crystallization in the circumstellar region or protoplanetary disk, or a sampling bias resulting from the easier recognition of crystalline grains during FIB preparation for TEM analyses. The amorphous grain (LCM01b_Si_PG07) is distinguished by its unusual Fe-rich, Ca-bearing, but Al-poor composition. The enrichment of Ca, together with abundant Fe, without corresponding Al enrichment is not readily explained by direct condensation of the present composition. The formation of a Ca-bearing amorphous silicate precursor followed by chemical modification involving Fe enrichment through interaction with the surrounding environment.

[1] Nittler, L. R. and Ciesla F. (2016) ARAA 54, 53., [2] Takigawa, A., et al. (2019) ApJL 878, L7., [3] Seifert et al. (2022) MAPS 57, 1119., [4] Takigawa, A., et al. (2014) GCA 124, 309., [5] Hashizume, H. (2026) M.Sc. thesis, U-Tokyo.

Speaker: Hiroyuki Hashizume (Department of Earth and Planetary Science, The University of Tokyo)

6:00 PM → 9:00 PM Poster Session

6:00 PM $^{24}Mg(p,\gamma)^{25}Al$ at LUNA

$\rm^{24}Mg(p,\gamma)^{25}Al$ plays a key role in the Mg–Al cycle, e.g. influencing the chemical evolution of asymptotic giant branch stars and the nucleo-synthesis of intermediate-mass nuclei, notably $\rm ^{26}$Al.
Despite its relevance, the reaction rate at stellar energies remains poorly constrained due to the extremely low cross sections within the sub-resonant Gamow window.

In this talk we present an experimental study on $\rm^{24}Mg(p,\gamma)^{25}Al$ carried out at the Laboratory for Underground Nuclear Astrophysics
(LUNA), located at the low-background environment of the INFN Laboratori Nazionali del Gran Sasso (Italy). We focused on the experimentally accessible energy range between 200 and 400 keV, which includes one narrow resonance and a direct-capture (DC) component. Reaction $\rm \gamma$-rays were acquired using two different setups: a high-efficiency $\rm 4\pi$ BGO detector, optimized for cascade detection, and a HPGe detector.
For the first, a coincidence-based analysis technique was developed exploiting detector segmentation together with compound nucleus de-excitation pattern and energy-gating conditions. This allowed to enhance the detection sensitivity for weak DC signals.
With the second, also thanks to the the excellent energy resolution and stability of the LUNA - 400 accelerator, we improved the determination of the 223~keV resonance energy and provided an independent study of the DC cross section.

Both the measurement campaigns and their results will be presented.

Speaker: David Rapagnani (University of Naples "Federico II")

6:00 PM 7Be + n Destruction Channels and the Cosmological Lithium Problem

The cosmological lithium problem [1] remains one of the major unresolved issues in nuclear astrophysics. It is related to the production and destruction channels of primordial $^{7}$Be, the main source of $^{7}$Li. Though the production channels of $^{7}$Be are well studied [2], improved measurements are required in the destruction reactions. The dominant neutron-induced destruction channels, $^{7}$Be$(n,p)^{7}$Li, $^{7}$Be$(n,p_{1})^{7}$Li$^{}(0.478)$, and $^{7}$Be$(n,\alpha)\alpha$, were previously investigated using the Trojan Horse Method (THM) through measurements of the $^{7}$Be + $d$ reaction at 3.16 MeV/u [3]. This resulted in a 10% reduction of the lithium discrepancy. Later, an indirect study of the $^{7}$Be$(n,p_{1})$ channel by Iwasa et al. [4] reported a significantly smaller cross section, implying a smaller contribution of this channel to the cosmological lithium problem than that inferred in Ref. [3]. In this work, we make a detailed study of the destruction channels of $^{7}$Be with neutrons via indirect methods. The experiment was carried out at HIE-ISOLDE, CERN, with a 5 MeV/u $^{7}$Be beam on a CD$2$ target [5]. The $^{7}$Be$(n,\alpha)\alpha$ reaction is studied via the THM, while the $^{7}$Be$(n,p_{1})$ cross section is derived from the $\Gamma_{p_{1}}/\Gamma_{p_{0}}$ ratios extracted from the $^{7}$Be$(d,p)^{8}$Be$^{}(p)^{7}$Li$^{*}$ reaction, as the $\Gamma_{p_{0}}$ values of the relevant excited states in $^{8}$Be are well known [6]. The present results lead to a few percent improvement in the lithium discrepancy. In addition, the $\Gamma_{p_{1}}/\Gamma_{p_{0}}$ ratios for the 20.9 MeV $(4^{-})$ and 21.5 MeV $(3^{+})$ states in $^{8}$Be are determined for the first time.

References:
1. A. Coc et al., Astrophys. J. Lett. 600, 544 (2004).
2. Carmona-Gallardo et al., Phys. Rev. C 86, 032801 (2012) (R).
3. S. Hayakawa et al., Astrophys. J. Lett. 915, L13 (2021).
4. N. Iwasa et al., Phys. Rev. C 112, 035801 (2025).
5. Sk M. Ali et al., Phys. Rev. Lett. 128, 252701 (2022).
6. L. Damone et al., Phys. Rev. Lett. 121, 042701 (2018).

Speaker: Sayan Samanta (Bose Institute, Kolkata, India)

6:00 PM A Hybrid Treatment of Baryon Degeneracy in Neutrino Transport for Core-Collapse Supernovae

We present neutrino-transport calculations for core-collapse supernova explosions (CCSNe), treating both degenerate and non-degenerate baryonic matter. Because neutrino–nucleon interactions are strongly affected by baryon degeneracy through Pauli blocking, the high-density region near the neutrinosphere requires careful phase-space integrations for the participating nucleons.

To address this issue, we develop a hybrid model that includes nucleon-degeneracy effects in Urca processes and neutrino-pair production within the neutrino-transport equation. The resulting CCSN simulations yield the evolution of the proto-neutron-star radius and shock-wave radius, and demonstrate the impact of baryon degeneracy on neutrino propagation.

Speaker: Myung-Ki CHEOUN (Soongsil University)

6:00 PM A Na-rich Actinide-boost r-II Candidate: The Chemo-kinematic Origin of LAMOST J015857.38+382834.7

We present a chemo-kinematic study of an extremely metal-poor giant LAMOST J015857.38+382834.7 (hereafter J0158) with [Fe/H] = -3.46. J0158 shows an unusual light-element pattern, with strong Na enhancement but no strong carbon enhancement, consistent with globular cluster-like second-population chemistry. Its high [Eu/Fe] = +1.6, and low Ba abundance classify it as a strongly r-process-enhanced r-II star. The high [Th/Fe] = +2.0 implies [Th/Eu] ≈ +0.4, making J0158 a promising actinide-boost r-II candidate, though further Th/U confirmation is needed. A pair-instability supernova (PISN) origin is disfavored because J0158 is Na-rich and neutron-capture-rich, unlike PISN candidates that show very low Na and weak neutron-capture enrichment. Its orbit places it near the Wukong/LMS-1 substructure, suggesting formation in an accreted dwarf-galaxy system locally enriched by a rare r-process event.

Speaker: Dayoung Byun (Chungnam National University)

6:00 PM A Near-Infrared Spectroscopic Search for Multiple-Population Signatures in NGC 1978

NGC 1978 is one of the youngest massive globular clusters (GCs) in the Large Magellanic Cloud, with reported photometric multiple-population (MP) signatures. We present a high-resolution near-infrared abundance analysis of 19 red giant branch-like stars in NGC 1978 using H- and K-band IGRINS spectra. Stellar parameters and abundances of C, N, O, Na, Mg, Al, Si, Ca, Ti, and Ce were derived through synthetic spectral fitting. The sample has a mean [Fe/H] = -0.49 with a scatter of 0.04 dex, indicating no large iron spread. The clearest feature is a C–N anticorrelation, while O varies only weakly, and the total C+N+O abundance remains nearly constant. This suggests redistribution among C, N, and O rather than a change in total CNO content. Na and Al are not clearly enhanced in the N-rich stars, Mg shows no obvious depletion, and Ce remains nearly uniform. These results give no strong evidence for enrichment by supernovae or asymptotic giant branch stars. We also find a tentative spatial trend in [N/C] along a preferred projected axis. Overall, NGC 1978 appears to host a mild MP-like chemical pattern mainly traced by C and N, rather than a fully developed old-GC-like MP.

Speaker: Mr Jaehyun Kim (Chungnam National University)

6:00 PM A Stellar Thermometer $^{176}$Lu/$^{176}$Hf of the Main $s$-Process in AGB Stars

The $^{176}$Lu ($t_{1/2}\sim$36 Gyr) and $^{176}$Hf are only produced by the main component of the slow neutron capture process (main $s$-process) in AGB stars.
The nucleosynthesis of the isomeric state of $^{176}$Lu$^{m}$ ($t_{1/2}\sim$3 h) dominates the $^{176}$Lu/$^{176}$Hf ratio because it cannot reach the thermal equilibrium with the ground state $^{176}$Lu$^{g}$ at the temperature of the main $s$-process.
We made a comprehensive nucleosynthesis including the $^{176}$Lu isomeric state in the main $s$-process during interpulse phases of two metal-poor stars (LP625$\_$44 and CS31062-012).
The isotopic ratio of $^{176}$Lu/$^{176}$Hf is 0.69 in two stars, which is independent from stellar metalicity, indicating that the ratio can be a stellar thermometer of the main $s$-process in AGB stars.

Speakers: Xinxu Wang (Beihang University), Yudong Luo

6:00 PM An Actinide-boost r-I Star as a Fossil Record of Early r-process Enrichment: Gemini/GHOST Abundance Analysis of LAMOST J122216.86−063345.26

We present a detailed chemical abundance analysis of LAMOST J122216.86−063345.26 (J1222), an actinide-boost r-I star observed with Gemini-S/GHOST. J1222 is a very metal-poor giant with [Fe/H] = −2.45 and is dynamically associated with the I’itoi substructure, making it a valuable tracer of early chemical enrichment in a system accreted into the Milky Way. From 43 measured elements, we find [Eu/Fe] = +0.61 and [Ba/Eu] = −0.52, classifying J1222 as an r-I star. Despite its moderate Eu enhancement, it shows a clear actinide-boost signature, with [Th/Dy] = −0.74. We also derive upper limits for U and Pb, which further constrain its neutron-capture abundance pattern. This combination suggests that actinide production is not simply set by the overall level of r-process enhancement. We interpret the abundance pattern of J1222 in relation to compact-object merger enrichment, including NSM and NS–BHM scenarios, focusing on neutron-rich ejecta, post-merger outflows, and the enriched gas from which the star formed. As a fossil record within the I’itoi substructure, J1222 connects the nucleosynthetic conditions of early r-process enrichment to the chemical evolution of an accreted system, and ultimately to the assembly history of the Milky Way halo.

Speaker: Miji Jeong (Korea Astronomy and Space science Institute (KASI))

6:00 PM An Observational Discrepancy in the Fuel Budget of Superbursts

X-ray bursts are thermonuclear explosions that occur when accreted material on the surface of a neutron star reaches critical conditions. Superbursts are exceptionally energetic events, lasting several hours or longer and releasing more than two orders of magnitude more energy than ordinary X-ray bursts. They are thought to involve carbon burning. Previous studies have suggested that the fuel mass inferred from standard thermal cooling models exceeds the mass estimated to have been supplied by accretion. However, because only one superburst had been detected from each source during the observational period, it has been difficult to quantitatively investigate the origin of this discrepancy.

In this study, we investigate this issue using sources with two or more detected superbursts. We analyzed approximately 31 years of long-term monitoring data from RXTE/ASM, Swift/BAT, and MAXI/GSC for the low-mass X-ray binaries Aql X-1 and 4U 1608–52. The total accreted mass between superbursts was estimated by assuming that the persistent bolometric flux is proportional to the mass-accretion rate and integrating the persistent emission over time. Instrument count rates were converted to bolometric fluxes using conversion factors that depend on the spectral state. For MAXI/GSC, we additionally evaluated fluxes from spectra integrated over selected intervals. The inferred accreted masses are $(0.4–0.8)\times10^{25}$ g for Aql X-1 and $(1.2–1.8)\times10^{25}$ g for 4U 1608–52. In contrast, cooling-model fits to the superburst light curves yield burned fuel masses of $(1.1–2.0)\times10^{25}$ g and $(8–10)\times10^{25}$ g, respectively, assuming burning over the entire neutron-star surface. Thus, the fuel mass inferred from the cooling model exceeds that supplied by accretion between superbursts. This result suggests that conventional cooling models may need to be revisited. Possible interpretations include localized burning on the neutron-star surface and a carbon reaction rate enhanced relative to the standard theoretical value.

Speaker: Amira Aoyama (Tokyo University of Science / RIKEN)

6:00 PM Anomalous Bursting Regime in the Clocked Burster GS 1826−238

Type-I X-ray bursts are thermonuclear explosions on the surfaces of accreting neutron stars (NSs). During these bursts, the rapid proton-capture process (rp-process) is thought to synthesize heavier nuclei and leave observable imprints on the burst light curves. While most X-ray bursters exhibit irregular burst recurrence times and profiles, only a few sources, known as “clocked” bursters, display highly regular bursting activity. These systems provide a unique opportunity to constrain the properties of accreting NSs and accreted material through detailed comparisons between observations and theoretical models.
We report the discovery of an anomalous bursting regime in the prototypical clocked burster GS 1826−238 using observations with the CubeSat X-ray observatory NinjaSat and NuSTAR. In May 2025, GS 1826−238 underwent a soft-to-hard state transition for the first time in a decade. During the subsequent hard state, NinjaSat observations revealed a new clocked-bursting phase with an unprecedentedly short recurrence time of $t_{\rm rec} = 1.603 ± 0.040\ {\rm hr}\ (1\sigma)$. Previous observations showed that the burst recurrence time decreases with increasing mass accretion rate, reaches a minimum value of ~3 hr, and then increases again. The observed recurrence time of 1.6 hr is therefore nearly a factor of two shorter than the previously observed minimum. In addition, the bursts exhibited reduced blackbody normalization and fluence compared with earlier clocked-bursting epochs. NuSTAR observations in February 2026 independently identified another short-recurrence phase with $t_{\rm rec} = 1.91±0.06\ \rm hr$, confirming that this behavior persists over multiple epochs.
The observed recurrence times are difficult to reconcile with the conventional picture in which bursts ignite uniformly over the NS surface. We propose instead that fuel accumulated over only a fraction of the stellar surface, resulting in an enhanced local accretion rate. This scenario naturally explains the unusually short recurrence times together with the reduced emitting area and burst fluence. Our results demonstrate that even for GS 1826−238, the benchmark source for observation–model comparisons of thermonuclear bursts, more realistic models incorporating multidimensional accretion may be required.

Speaker: Tomoshi Takeda (Kyoto University)

6:00 PM ASFIN collaboration studies of γ-induced reactions at the HIγS facility

γ-induced reactions like (γ, n), (γ, p), and (γ, α) are of interest in several astrophysical scenarios such as Big Bang Nucleosynthesis and the Li-problem, Si-burning in massive stars, p-process. Recently, the ASFIN collaboration, in the framework of an international collaboration, has started an experimental campaign at the High Intensity Gamma-Ray Source (HIγS) dedicated to the study of different γ-induced reactions such as $^{7}$Li(γ,t), $^{102}$Pd(γ,p),$^{102}$Pd(γ,α), $^{112}$Sn(γ,p), $^{112}$Sn(γ,α) and $^{24}$Mg(γ,α). Such kinds of experiments require, among others, a precise determination of the γ-beam flux. The $^{197}$Au(γ,n)196Au reaction is commonly used as a reference process to measure the gamma beam intensity in photonuclear reaction experiments. However, at energies higher than 14.7 MeV, the cross-section values of the $^{197}$Au(γ,n)$^{196}$Au reaction available in the literature (both from experiments and theory) exhibit conflicting values. In this context, a new measurement of the $^{197}$Au(γ,n)$^{196}$Au reaction cross-section was performed at the HIγS facility using the activation method.
In this presentation, an overview of the ASFIN experimental campaign will be provided. Moreover, the experimental procedure and preliminary results of the new measurement of the $^{197}$Au(γ,n)$^{196}$Au reaction cross-section will be shown.

Speaker: Giuseppe Gabriele Rapisarda (DFA-UniCT & LNS-INFN)

6:00 PM Best Reaction Target To Determine Proton Distribution Radii of Atomic Nuclei

We found that a heavy target such as Pb is most suitable for determining the proton distribution radii of unstable nuclei through charge-changing cross-section ($\sigma_\text{cc}$) measurements. As a heavy ion probe, low-$Z$ targets are routinely used to determine nucleon distribution radii of unstable isotopes. This approach has recently been extended to study proton distribution radii from $\sigma_\text{cc}$ measurements. However, empirical scaling factors have to be introduced to apply the Glauber models. In the present work, we systematically investigated the scaling factor using 39 new $\sigma_\text{cc}$ data of 18 $p$-shell nuclei on hydrogen, carbon, silver, and lead targets at around 240 MeV/nucleon. Together with the existing data, we reveal a universal dependence of the scaling factor on both the masses of target nuclei and the separation energies of projectile nuclei. The scaling factors decrease with increasing target-nucleus mass and converge to 1 for the highest-Z target, making the scaling unnecessary. We conclude that instead of a low-Z target, employing a heavy target such as Pb in $\sigma_\text{cc}$ measurements is the best option to determine the proton distribution radii of unstable nuclei.

Speaker: Jun-yao Xu (Beihang University)

6:00 PM Can a Varying Higgs VEV Solve the Cosmic Lithium Problem?

The discrepancy between the observationally inferred primordial 7Li abundance and the theoretical prediction of Standard Big Bang Nucleosynthesis (SBBN) remains one of the longstanding unsolved problems in modern cosmology. In addition, recent spectroscopic observations of metal-poor extra-galactic systems have reported a lower primordial 4He abundance than previously reported from observations of metal-poor field stars in the Milky Way. This new 4He abundance constraint appears to be inconsistent with the standard model of elementary particles and fields, which describes the breaking of lepton and baryon symmetries in the early Universe.
We have recently proposed [1] that a time-varying Higgs field may provide a unified resolution to these discrepancies involving the primordial abundances of 7Li and 4He. Elementary particles and nuclei acquire their masses through their coupling to the Higgs field. Consequently, the Higgs vacuum expectation value (VEV) determines the Fermi constant as well as the electron and quark masses. Any deviation of the Higgs VEV from its present-day value in the early Universe would modify electroweak and strong interactions, thereby affecting proton–neutron conversion rates and many thermonuclear reaction rates that play the critical roles in BBN of the light elements.
In this work, we present a detailed analysis of these effects on BBN and investigate whether concordance can be achieved among the observed primordial abundances of the light elements D, 4He, and 7Li, cosmological constraints from cosmic microwave background (CMB) fluctuations and anisotropies, and the underlying framework of particle physics.

[1] H. Feng, Y. Luo, T. Kajino, B. Sun, and T. Shima;
Phys. Rev. D (2026), submitted and under review.

Speakers: Hongrui Feng (Beihang University), Yudong Luo

6:00 PM Characterizing the Chemical Enrichment Histories of the Milky Way’s Accreted Substructures Using Metal-Poor Stars

We present a chemical and dynamical analysis of 22 metal-poor stars with [Fe/H] < –1.0 selected from Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). High-resolution spectra were obtained with Gemini-N/GRACES and Gemini-S/GHOST, enabling the determination of stellar atmospheric parameters and elemental abundances spanning light, α, iron-peak, and neutron-capture elements. Combining these chemical abundances with Gaia-based dynamical information, we associate the majority of the sample with known Milky Way (MW) substructures, including Gaia-Sausage-Enceladus (GSE), Wukong/LMS-1, and I’itoi. We identify more than half of the sample as r-process-enhanced stars, indicating strong neutron-capture enrichment. Abundance trends of [Mg/Fe], [Eu/Mg], [Ba/Mg], and [Eu/Ba] indicate distinct enrichment histories for each substructure. These results show that metal-poor stars can constrain the nucleosynthetic pathways and progenitor properties of accreted MW systems.

Speaker: Young Sun Lee (Chungnam National University)

6:00 PM Chiral Microscopic Optical Potentials for νp Process Nucleosynthesis in the Ge Ga Region

νp-process in supernovae produces light p-nuclei. The (n,p) reactions on Ge isotopes control how much matter flows toward heavy nuclei, but existing reaction rates rely on phenomenological models with unknown uncertainties.
We computed new (n,p) reaction rates in the Ge-Ga region using microscopic optical potentials derived from chiral nuclear forces, compared them with the standard JINA library, and tested their impact on nucleosynthesis.
The chiral potentials give systematically different rates. The choice of optical potential shifts the final abundance pattern of p-nuclei in ways that cannot be covered by simply scaling the old rates up or down. Notably, neighboring isotopes respond very differently — one reaction can dramatically redistribute matter along the mass chain while the next hardly matters at all. This suggests that optical potential uncertainties, rather than statistical model parameters, are the dominant source of error for these reactions.

Speaker: Tong Zhang (Institute of Modern Physics, Chinese Academy of Sciences)

6:00 PM Comparison of low-energy 12C+ 12C and 12C+ 13C fusion reaction through compound-nucleus spectra

The $^{12}\mathrm{C} + ^{12}\mathrm{C}$ fusion reaction plays a key role in several astrophysical explosive phenomena. However, the cross section for the $^{12}\mathrm{C} + ^{12}\mathrm{C}$ fusion reaction at the relevant energy region is difficult to determine because of both experimental limitations and strong resonant structures. We develop a reaction model that explicitly treats the $\mathrm{C} + \mathrm{C}$ channel and the $\mathrm{Mg}$ channel. The model reproduces the contrasting resonant structures and smooth energy dependence observed in the $^{12}\mathrm{C} + ^{12, 13}\mathrm{C}$ systems. In the analysis, the experimentally observed upper limit behavior of $^{12}\mathrm{C} + ^{13}\mathrm{C}$ to $^{12}\mathrm{C} + ^{12}\mathrm{C}$ fusion cross section is used as a practical empirical constraint.

Speaker: Kosei Nagao (Kyoto University)

6:00 PM Constraints on New Physics Based on Supernova Explodability

Core-collapse supernovae are powerful cosmic laboratories to probe physics beyond the Standard Model. While exotic particles can alter explosion dynamics, previous studies relying on post-processing could not fully capture the non-linear feedback on multi-dimensional hydrodynamic features. In this talk, we report constraints on new physics obtained through two-dimensional neutrino-radiation hydrodynamic simulations.

First, we investigate eV-mass active-sterile neutrino oscillations ($\nu_e \leftrightarrow \nu_s$). Our simulations reveal that large mixing angles significantly reduce the electron-neutrino flux, suppressing neutrino-driven heating and preventing shock revival. Based on the observational fact that supernovae do explode, we establish a new constraint that excludes a substantial fraction of the parameter space favored by terrestrial experiments.

After that, we report results for dark photons (DPs). By performing simulations self-consistently coupled with DP production, we find that the DP cooling channel can lead to a failed explosion. Our results demonstrate that multi-dimensional hydrodynamic feedback is indispensable for evaluating astronomical signatures of novel particles in signals from supernova events.

Speaker: Kanji Mori (Fukuoka University)

6:00 PM Data-driven exploration of the neutron ${}^3$P${}_2$ pairing gap using Cassiopeia A neutron star observational data

The rapid cooling observed in the Cassiopeia A neutron star (CasA NS) is one of the most stringent tests for neutron-star cooling theory. While Cooper-pair breaking and formation (PBF) neutrino emission is a leading candidate, uncertainties remain regarding the PBF efficiency factor $q$ and the neutron ${}^3$P${}_2$ pairing gap. This work [1] explores in a data-driven manner how the optimized gap shape responds to variations of the PBF emissivity parameter within a fixed cooling setup. We introduce a novel gap parametrization, in which each parameter carries direct physical meaning and controls the gap amplitude, peak location, width, and asymmetry. Using a Fortran-based cooling code and the BSk24 equation of state, we perform parameter-space exploration guided by the CasA NS data. Global optimization is carried out with Optuna's tree-structured Parzen estimator, followed by local refinement using the Nelder-Mead method. The optimized solutions yield physically reasonable gaps with peak amplitudes $\Delta_\text{max}\approx0.5-0.6$ MeV. For $M=1.4M_\odot$, increasing $q$ drives the optimized gap and critical-temperature profiles toward smoother and more localized shapes, improving consistency with the observed trend. Models with $q\gtrsim0.4$ reproduce the decline rate within the $1\sigma$ confidence interval, whereas the baseline case $q\simeq0.19$ lies near the $3\sigma$ level. Our results suggest larger effective PBF emissivities than the baseline estimate. As a next step, we are undertaking Bayesian inference including uncertainties in mass, envelope composition, equation of state, pairing microphysics, and age offset [2]. In this talk, we will show how we can get deeper insight into dense nuclear matter by using precise observational data of neutron star surface temperatures, like CasA NS.

${}\;$
[1] Y. Nam and K. Sekizawa, Phys. Rev. C 113, 045807 (2026).
[2] K. Sekizawa and Y. Nam, in preparation.

Speaker: Dr Kazuyuki Sekizawa (Institute of Science Tokyo)

6:00 PM Direct measurement of astrophysically important (a,p) reactions using AToM-X active target TPC

Investigating (α,p) reactions is essential for understanding explosive stellar environments, such as X-ray bursts and core-collapse supernovae. However, direct measurements of (α,p) reactions with rare-isotope beams remain experimentally challenging, and previous studies have therefore relied largely on theoretical estimates and indirect approaches. An Active Target Time Projection Chamber (AT-TPC) provides a suitable detection system for such measurements, combining high detection efficiency with three-dimensional tracking in a thick gas target. A new Active Target TPC for Multiple nuclear physics eXperiments, AToM-X, is being developed at the Center for Exotic Nuclear Studies (CENS) for direct measurements of astrophysically important reactions. In this presentation, the development status of AToM-X and the approved experimental programs will be discussed including the direct measurement of the ¹⁷F(α,p)²⁰Ne reaction cross sections at CRIB in RIKEN.

Speaker: Dr Soomi Cha (Center for Exotic Nuclear Studies, Institute for Basic Science)

6:00 PM Dynamics of core-collapse supernovae with quark-matter cores

A first order phase transition to quark matter can provide a shock revival mechanism for core-collapse supernovae and a means to enhance the energy of the explosion. Recent studies have also noted the onset of radial oscillations of the core that can be excited when the equation of state allows the formation quark matter. Such oscillations may produce an observable signal in emitted neutrinos. In this work, expand on previous models in spherical symmetry by including effects neutrino-heated convection based upon Supernovae Turbulence in Reduced-Dimensionality (STIR). We analyze a set of solar-metallicity progenitor models from 14 - 40 $M_{\odot}$ in. We find that most models with turbulence tend to explode before reaching the secondary shock or oscillations from the phase transition. This implies that it may be difficult to observe the oscillations. Nevertheless, at least two models experience the onset of oscillations. We also analyze the source of the oscillations and show that they result when the quark matter coexistence region realizes an equation of state with an adiabatic index of 4/3. This occurs relatively far out in the star. The resulting oscillations are not a pure breathing mode, but have a node at the radius where the adiabatic index crosses 4/3. We present semi-analytic models for the onset and frequency of the oscillations.

Speaker: Grant Mathews (University of Notre Dame)

6:00 PM Effective Binary Star Yields for stable and Radioactive Nuclides in Galactic Chemical Evolution

Nucleosynthetic yields from stars are key inputs for galactic chemical evolution models and are essential for understanding the origin and distribution of elements in galaxies. While most chemical evolution studies adopt single-star yields for massive stars, observations indicate that the majority of massive stars form and evolve in binary systems. Incorporating the effects of binary evolution into chemical evolution models remains challenging due to the complexity of binary interactions and the computational cost of population synthesis. In this work, we compute effective binary star yields, which provide a practical framework for including binary contributions in chemical evolution models with an approach analogous to single-star yields. These effective yields encapsulate the impact of binary interactions, such as mass transfer and binary birth distributions, on stellar nucleosynthesis without requiring explicit binary population synthesis. We incorporate these yields into chemical evolution models to study their effects on both stable elements and short-lived radionuclides, including 26Al, and 60Fe. By comparing chemical evolution models using standard single-star yields, primary yields, and effective binary yields, we quantify their effects on stable and radio nuclides abundances and explore their implications for galactic chemical enrichment and early solar system formation. In this presentation, we will share the insights into the role of binary evolution in shaping observed abundance distributions.

Speaker: Tejpreet Kaur (Indian Institute of Technology Kanpur, India)

6:00 PM Effects of $\Lambda NN$ and $\Lambda\Lambda N$ Three-Body Interactions on Hyperonic Neutron Star Equations of State

The observations of massive neutron stars provide a stringent constraint on the nuclear matter equation of state (EoS). While exotic particles such as hyperons may emerge in high-density neutron-star matter, their appearance generally softens the EoS, making it difficult to sustain neutron stars with masses of $2M_\odot$ or heavier. This apparent inconsistency between hyperonic EoS models and observations is known as the hyperon puzzle. Density-dependent repulsive $\Lambda NN$ and $\Lambda\Lambda N$ three-body interactions may provide a possible mechanism for recovering stiffness, but their effects on neutron-star structure are still unclear.

In this work, we investigate how $\Lambda NN$ and $\Lambda\Lambda N$ three-body interactions affect the neutron-star EoS and mass-radius relation. We construct beta-equilibrated $npe\mu\Lambda$-matter EoSs based on Skyrme-type energy-density functionals, varying the parameters $(A_3,\beta)$ and $(C_3,\gamma)$ associated with $\varepsilon_{\Lambda NN}=A_3 n_\Lambda n_N^{\beta+1}$ and $\varepsilon_{\Lambda\Lambda N}=C_3 n_\Lambda^2 n_N^\gamma$, respectively. The Tolman--Oppenheimer--Volkoff equation is then solved to obtain the corresponding mass--radius relations.

From the numerical calculations, we find that larger coupling constants $A_3$ and $C_3$ and smaller exponents $\beta$ and $\gamma$ tend to increase the maximum mass. The $\Lambda\Lambda N$ interaction mainly stiffens the EoS after $\Lambda$ particles appear, whereas the $\Lambda NN$ interaction can also change the density region where hyperons become important, sometimes producing abrupt softening of the EoS. We analyze the number of extrema of the EoS and, when appropriate, consider the Maxwell construction for a mixed-phase scenario.

In this talk, we will discuss how density-dependent repulsive $\Lambda NN$ and $\Lambda\Lambda N$ three-body interactions modify hyperonic neutron-star EoSs, how these modifications are reflected in the mass-radius relation and the maximum mass, and how extrema of the EoS affect the interpretation of the results.

Speaker: Taeho Lee (Institute of Science Tokyo)

6:00 PM Effects of extra neutrino emissivities in kaon condensation on thermal evolution of neutron stars

Thermal evolution of neutron stars, as well as mass and radius observations, brings about important astrophysical information on properties of highly dense matter in inner core of a neutron star. As a candidate of novel hadronic phase, a coexistent phase of kaon condensation and hyperon-mixed matter [abbreviated to (Y+K) phase] has been extensively studied from both theoretical and observational viewpoints. In the previous studies, however, the (Y+K) phase had a problem that it significantly softens the equation of state (EOS) , so that it cannot give massive neutron stars as large as two solar mass.  The problem has been recently solved with inclusion of universal three-body forces between baryons. It has been shown that sufficiently stiff EOS including the (Y+K) phase has been obtained, being enough to be consistent with the observations of masses and radii of massive  neutron stars.
  In the presence of the (Y+K) phase, the rapid cooling mechanisms via neutrino emissions, i.e.,  the kaon-induced Urca (KU) processes, become possible.
Recently we have obtained the cooling history of compact stars with the KU processes with use of the EOS including the (Y+K) phase ; The effects of the KU processes on the time evolution of surface temperature have been investigated on the assumption of the density dependence of the proton $^1$S$_0$ pairing strengths.
 In this talk, we further discuss in detail main neutrino emission mechanisms unique to the (Y+K) phase by obtaining the density-dependence of neutrino emissivities for the KU processes associated with both nucleons and hyperons ($\Lambda$ and $\Xi^-$ hyperons). We clarify the role of such extra neutrino emission processes on the cooling of neutron stars by comparing with the recently detected cold neutron stars.

Speaker: Prof. Takumi Muto (Chiba Institute of Technology)

6:00 PM Effects of Multineutron States on Nuclear Composition in Supernova Matter

We investigate the possible impact of multineutron states on nuclear composition under conditions relevant to core-collapse supernovae and proto-neutron stars. We examine the role of multineutron states, such as dineutrons and tetraneutrons, which may emerge from neutron correlations in neutron-rich matter. We extend a statistical model of nuclear matter by incorporating dineutron and tetraneutron degrees of freedom.
We find that dineutrons and tetraneutrons can become abundant at high densities and in neutron-rich environments, thereby reducing the abundance of unbound neutrons. Their formation also decreases the abundance of neutron-rich nuclei. This redistribution increases the abundance of unbound protons and, in turn, enhances the abundance of heavy nuclei.
These results suggest that multineutron correlations can modify the nuclear composition of neutron-rich supernova matter and may affect neutrino opacities. In particular, the increase in unbound protons may enhance electron-type neutrino emission, while the enhanced abundance of heavy nuclei may increase coherent neutrino scattering. These effects could influence neutrino heating and neutrino trapping in core-collapse supernovae and proto-neutron stars.

Speaker: Tatsuya Matsuki (The University of Tokyo)

6:00 PM Effects of the 2SC+$<dd>$ phase on the cooling of compact objects

Compact objects such as neutron stars are composed of matter so dense that they can be likened to a single, massive atomic nucleus. The density at their cores exceeds that of a nuclear nucleus, and it is predicted that various states of matter—not found in ordinary atomic nuclei—will emerge there. The state of matter within these objects has a significant impact on neutrino emission, which can be observed through the object’s surface temperature. By comparing the observed temperatures of compact objects with theoretical calculations, we can explore the state of matter inside them.

We investigated the thermal evolution of compact objects, assuming colour superconducting quark matter exists within them. Since multiple pairings are conceivable in the colour superconducting state, in this study we assumed that one of the following phases would emerge: the CFL phase, the 2SC phase, or the 2SC+$<dd>$ phase, which takes into account quark-hadron continuity of ${}^3P_2$ superfluidity. We found that considering the 2SC+$<dd>$ phase allows us to explain the observational results for compact objects.

Speaker: Tsuneo NODA (Kurume Institute of Technology)

6:00 PM Estimation of the slope parameter L using magnetar asteroseismology

By identifying quasi-periodic oscillations reported in FRB 20240114A (from the Five-hundred-meter Aperture Spherical Telescope) with neutron star crustal torsional oscillations, together with experimental constraints on the nuclear saturation parameter, the incompressibility $K_0$, we constrain the mass and radius of an extragalactic neutron star at redshift $z=0.13$. Identifying the low-order QPO frequencies as fundamental oscillations, and frequencies of 567.7 Hz or 655.5 Hz (rest frame) as first overtone candidates implies neutron star mass ranges of $1.00-1.55 M_\odot$ or $1.17-1.76 M_\odot$, respectively. Additionally, accounting for the nuclear parameter dependence of low-mass neutron star structure yields an estimated radius of $12.5-13.5$ km. Simultaneously, we also constrain the nuclear saturation parameter, namely the density dependence of the nuclear symmetry energy, $L$, and determine it to be $L=59.5-96.8$ MeV, which is broadly consistent with the previous constraints on $L$ obtained from the experiments and astronomical observations. This can be investigated with upcoming FRB surveys over a broad range of redshifts and more elaborate data analyses.

Speaker: Prof. Hajime SOTANI (Kochi University)

6:00 PM Exclusive Indirect Measurement at the ISAC-II Facility of the 22Ne(α,γ)26Mg Reaction for s-process Nucleosynthesis

Around half the elements heavier than iron originate from the astrophysical slow neutron-capture (s-) process. This mechanism occurs within the stellar environments of asymptotic giant branch and massive stars, where the endothermic 22Ne(α,n)25Mg reaction is one of the main sources of neutrons. This reaction competes with 22Ne(α,γ)26Mg across the astrophysical temperature regime 150 – 300 MK (Ecm = 300 – 750 keV). To constrain both the temperature at which neutron production is activated and how much 22Ne is converted to neutrons, it is essential to understand the contribution of resonances to the reaction rates. Several resonances for these 22Ne+α reactions have been directly measured down to Ecm = 706 keV. However, below 700 keV there remains considerable disagreement between experimental studies on the resonance strengths of crucial states. To confront this weakly-constrained energy region, at the ISAC-II beamline in TRIUMF (Canada) we performed a dedicated study of crucial 26Mg states using the indirect 22Ne(7Li,t)26Mg reaction. A 22Ne beam at 3 MeV/nucleon bombarded a 500 μg/cm2 LiF target, following which the gamma-rays and 26Mg recoils were measured using the TIGRESS and EMMA systems, respectively. The tritons were detected at backward laboratory angles using a Micron S3 silicon detector. We will present the setup and preliminary analysis from this study, the results of which are expected to enhance our understanding of these essential neon-burning reactions in stellar nucleosynthesis.

Speaker: Thomas Chillery (University of Naples)

6:00 PM Exploring the Origin of Elemental Abundances in Cassiopeia A

A massive star explodes as a core-collapse supernovae at the end of life and the explosion can be observed as a supernova remnant (SNR) over up to about ten thousand years. The elemental abundances observed in SNRs provide important clues to both nucleosynthesis in pre-supernova evolution and the supernova explosion. Recent observations of Cassiopeia A (Cas A), which is one of the best-studied SNR, with XRISM/Resolve have revealed detailed abundances of various elements, including odd-Z elements such as Cl and K (XRISM Collaboration 2025; Sato et al. 2026). These observations point out the possibility that the progenitor of Cas A experienced a shell merger caused by convective mixing shortly before core collapse. However, it remains unclear whether the observed elemental abundances originate from pre-supernova evolution or explosive nucleosynthesis, which burning they reflect, and whether each observed region can be reproduced with a single burning layer.

In this study, we calculate 1D stellar evolution and supernova nucleosynthesis and compare the results with the elemental abundance measurements of Cas A. We focus particularly on the newly observed odd-Z elements, including Cl and K, as well as Fe-peak elements, to investigate the relative contributions of pre-supernova evolution and explosive nucleosynthesis.

Our results suggest that the observed elemental abundance ratios cannot be explained by a single burning layer and may require contributions from multiple burning layers.

In this talk, we discuss the origin of the elemental abundances observed in different regions of Cas A.

Speaker: Ryota Hatami (SOKENDAI/NAOJ)

6:00 PM Fast Neutrino Flavor Conversion and Its Possible Impact on Core-Collapse Supernova Nucleosynthesis

Core-collapse supernovae are promising sites of explosive nucleosynthesis, where the electron fraction of the ejecta is strongly influenced by the spectra and angular distributions of electron neutrinos and antineutrinos. Recent multidimensional simulations suggest that fast neutrino flavor conversion can occur in the decoupling region of core-collapse supernovae, potentially modifying the neutrino radiation field before it shapes the composition of the outflow. However, the connection between nonlinear flavor conversion and nucleosynthesis remains insufficiently understood.

In this contribution, I discuss how collective neutrino flavor conversion may affect supernova nucleosynthesis through changes in the local $\nu_e$ and $\bar{\nu}_e$ distributions, charged-current reaction rates, and the resulting electron fraction $Y_e$. I focus on the possible occurrence of fast flavor conversion in multidimensional core-collapse supernova environments and examine how flavor-modified neutrino distributions could be incorporated into nucleosynthesis post-processing calculations. Particular attention is given to how angular crossings and nonlinear flavor equilibration may alter the local $\nu_e$ and $\bar{\nu}_e$ radiation fields, as well as to the theoretical uncertainties involved in applying local flavor-conversion prescriptions to dynamical ejecta.

This study aims to clarify which aspects of flavor conversion are most relevant for nucleosynthesis predictions and to identify the conditions under which flavor effects may leave observable imprints on supernova ejecta composition.

Speaker: Liu Jiabao (Waseda University)

6:00 PM Formation, evolution, and nucleosynthesis of the dwarf satellites of the Milky Way

We analyze the chemical evolution of alpha elements and iron for sumulated dwarf galaxies in Milky-Way-like plane-of-satellite systems for the TNG50 large-scale cosmological simulation. We first analyze the formation of the 11 most lumious satelites that form the plane of satellites around the MIlky Way. Having identified simulated systems that match the properties of the Milky-Way satellites, we analyze in detail their formation and alpha-element nucleosynthesis. We show that the direct nucleosynthesis from the simulations is sometimes a poor fit to the observations. However, simple corrections for the contribution of iron from double-degenerate white dwarf mergers and a diminished efficiency of mixing of ejecta from core collapse supernovae and Type IA supernovae can account for the apparent discrepancies.

Speaker: Grant Mathews (University of Notre Dame)

6:00 PM Galactic chemical Evolution of r-process elements

The origin of the heaviest elements is still a matter of debate. For the rapid neutron capture process (r-process), multiple sites have been proposed, e.g., neutron star mergers and (sub-classes) of supernovae. R -process elements have been measured in a large fraction of metal-poor stars. Galactic archaeology studies show that the r-process abundances among these stars vary by over 2 orders of magnitude. On the other hand, abundances in stars with solar-like metallicity do not differ greatly. While the large scatter at low metallicities might point to a rare production site, why is there barely any
scatter at solar metallicities?
In this poster, I will discuss chemical evolution scenarios that provide an explanation for the observed abundance features of r-process elements in our Galaxy, especially at the lowest metallicities.

Speaker: Benjamin Wehmeyer (University of Wrocław)

6:00 PM Galactic chemical Evolution with short lived radioactive isotopes

Studying the galactic chemical evolution with short lived radioisotopes (SLRs) has a significant advantage over using stable elements: Due to their radioactive decay, SLRs carry additional timing information on astrophysical nucleosynthesis sites.

We can use meteoritic abundance data in conjunction with a chemical evolution model to constrain the physical conditions in the last rapid neutron capture process event that polluted the early Solar system prior to its formation [1].

Further, with the help of detections of live SLRs of cosmic origin in the deep sea crust [2], we can use these data in a 3-dimensional chemical evolution code to explain why different classes of radioisotopes should often arrive conjointly on Earth, even if they were produced in different sites (e.g., neutron star mergers, core-collapse/thermonuclear supernovae) [3].

Finally, we included radioisotope production into a cosmological zoom-in simulation to create a map of Al-26 decay gamma-rays indicating areas of ongoing star formation in the Galaxy, consistent with the observations by the SPI/INTEGRAL instrument [4].

We provide predictions for future gamma-ray detection instruments (e.g., COSI) [5]

References:
[1] Côté et al., 2021 Science 371, 945
[2] Wallner et al., 2021 Science 372, 742W
[3] Wehmeyer et al., 2023 ApJ 944, 121
[4] Kretschmer et al., 2013 A&A 559, A9
[5] Wehmeyer et al., 2025 A&A 695, 190

Speaker: Benjamin Wehmeyer (University of Wrocław)

6:00 PM Gemini/GMOS Spectroscopy of Bright CEMP Candidates from LAMOST

Metal-poor stars preserve fossil records of early nucleosynthesis and the chemical evolution of the Milky Way (MW). Carbon-enhanced metal-poor (CEMP) stars are especially useful tracers of the MW’s earliest enrichment. We obtained medium-resolution (R ~ 4000) spectra with Gemini/GMOS for a sample of bright CEMP candidates selected from the LAMOST survey. We derive stellar atmospheric parameters and measure the abundances of key elements, including C, Mg, Sr, and Ba, which are essential for identifying CEMP stars and investigating their nucleosynthetic origins. The abundance patterns obtained from these observations enable preliminary classification of the targets into CEMP subclasses and provide insight into the chemical enrichment history of the early MW. These results establish a foundation for future high-resolution spectroscopic follow-up aimed at detailed chemical abundance studies of newly identified CEMP stars.

Speaker: Chang Mok Do (Chungnam National University)

6:00 PM Identifying Mono-Enriched Candidates among Extremely Metal-Poor Stars through Chemical Signatures

The earliest chemical enrichment in the Universe was driven by supernovae of Population III stars. Low-mass second-generation stars formed from gas polluted by these ejecta can survive to the present day as extremely metal-poor (EMP) stars in the Galactic halo. Their abundance patterns provide a fossil record of early nucleosynthesis and chemical evolution. However, an observed EMP star may have been enriched either predominantly by a single Population III supernova or by a mixture of several supernovae. Identifying mono-enriched candidates is therefore essential for using stellar abundances to infer the properties of individual first stars.
In this study, I develop a framework to identify mono-enriched candidates by connecting EMP-star abundances from the SAGA Database to Population III supernova yield models. Mock mono- and multi-enriched abundance patterns are constructed from theoretical Pop III yield models with varying progenitor mass and explosion energy, including dilution effects, and support-vector-machine classifiers are trained to distinguish the two cases. Cross-validation tests indicate that four-dimensional abundance-ratio classifiers balance performance and observational applicability, with C/iron-peak ratios emerging as effective diagnostics.
I apply an ensemble of selected classifiers to SAGA EMP-star abundances, propagate observational uncertainties by resampling, and assign mono-likeness scores to individual stars. By examining the performance of classifiers with different abundance-ratio combinations, I identify which elements and abundance ratios are most important for selecting mono-enriched candidates in observed EMP samples. This framework provides a physically motivated way to select stars that may preserve relatively clean chemical signatures of individual Population III supernovae, forming a basis for future yield fitting and inference of first-star properties.

Speaker: Ryo Ishikawa (Tohoku University)

6:00 PM Impact of experimental mass of $^{70}$Kr on the $^{68}$Se waiting-point in the $rp$-process

The recent mass measurement of $^{70}$Kr using the $B\rho$-defined isochronous mass spectrometry yields a mass excess of $-41320(140)$ keV, indicating a 220-keV increase in binding energy compared to the AME2020 prediction. We utilize this experimental mass to probe its impact on the potential waiting point $^{68}$Se in $r$p-process and quantitatively constrain the $2p$-capture reaction flow that can bypass this waiting point. Our investigation shows that the more tightly bound nature of $^{70}$Kr enhances this $2p$-capture reaction flow up to a factor of four. This enhancement reduces the effective half-life of $^{68}$Se. A one-zone X-ray burst model calculations reveal that the higher flow of $^{70}$Kr has distinct effects on the tail structure of light curve and the final SnSbTe abundances in the ashes due to a stronger $r$p-process heating.

Speaker: MIN ZHANG (Institute of Modern Physics, Chinese Academy of Sciences)

6:00 PM Impact of Proximity Potential Models on the 12C+ 12C Fusion Reaction

The 12C+12C fusion reaction plays a crucial role in stellar carbon burning and the evolution of massive stars. However, significant uncertainties remain in the fusion cross sections and reaction rates at astrophysical energies. In this work, we systematically investigate the performance of various versions of the proximity potential formalism in describing the 12C+12C fusion process. Fusion cross sections are calculated using the one-dimensional barrier penetration model and compared with available experimental data. The corresponding astrophysical S-factors and thermonuclear reaction rates are also evaluated. Statistical analyses are performed to identify the potential models that best reproduce the experimental measurements. The results provide improved constraints on the 12C+12C reaction and help reduce nuclear physics uncertainties in stellar evolution calculations.

Keywords: Nuclear astrophysics, 12C+12C fusion, carbon burning, proximity potential, reaction rates.

Speaker: AZNI ABDUL AZIZ (INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA)

6:00 PM Impacts of recent nuclear reactions on the rp-proccess in X-ray bursts

Nucleosynthesis in Type I X-ray bursts, particularly the rp-process, provides an important connection between nuclear physics and astrophysical observations. However, many reaction rates relevant to explosive hydrogen burning remain experimentally unconstrained, and theoretical predictions still involve substantial uncertainties. We investigate the astrophysical impact of a newly calculated set of theoretical reaction rates obtained with the Hauser-Feshbach code SMARAGD [1]. Using one-zone X-ray burst models covering a typical range of burst conditions, together with a reaction network optimized for rp-process nucleosynthesis, we compare the results based on the new SMARAGD rates with those obtained using standard reaction-rate libraries. Monte Carlo--based sensitivity calculations are also employed to evaluate the effects of reaction-rate uncertainties. We find that the updated theoretical rates can lead to moderate systematic changes in the rp-process path. Their impact on X-ray-burst light curves is generally limited, whereas more pronounced differences appear in the final abundances, especially for nuclei in the trans-iron region. These results suggest that systematic revisions of theoretical reaction rates may affect the interpretation of burst ashes even when their observable light-curve effects are modest. Our study highlights the importance of assessing theoretical reaction-rate uncertainties in rp-process nucleosynthesis. It also shows that Monte Carlo sensitivity studies are valuable for identifying influential reactions, but their interpretation requires caution in regions where many rates remain poorly constrained by experiment.

[1] T. Rauscher, EPJA 62, 35 (2026)

Speaker: Dr Nobuya Nishimura (Kogakuin University)

6:00 PM Josephson-Induced HQV-SQV Binding at the $^1S_0$-$^3P_2$ Interface and Its Implications for the Vortex Network Model of Pulsar Glitches

Pulsar glitches are sudden quasi-periodic increases in the rotation frequency of neutron stars, and are believed to originate from the dynamics of quantized vortices in the neutron superfluid interior. Recently, the vortex network model proposed by Marmorini et al.(2024) suggested that the coupling between $^3P_2$ half-quantized vortices (HQVs) in the outer core and $^1S_0$ singly-quantized vortices (SQVs) in the inner crust gives rise to a large-scale vortex network, providing a candidate mechanism for the diversity of observed glitch phenomena. However, the microscopic nature of this HQV-SQV interaction has not been investigated.
Using the Gross-Pitaevskii framework for the two-component $^1S_0$-$^3P_2$ coexistence phase, we perform two-dimensional simulations varying the density-density and Josephson coupling constants. We find that the Josephson term, arising from the relative phase between the two condensates, dominates over the density-density coupling and induces a strong HQV-SQV attraction. The resulting HQV-SQV-HQV bound state provides microscopic support for the boojum structure at the crust-core boundary envisioned in the vortex network model, and opens a new avenue for understanding the microscopic origin of vortex coupling relevant to pulsar glitch phenomena.

Speaker: Tatsuhiro Hattori (Institute of Science Tokyo)

6:00 PM Mass measurements of neutron-rich lanthanide isotopes via MRTOF mass spectrograph

The rapid neutron-capture process (r-process) is considered responsible for the production of approximately half of the elements heavier than iron in the universe. However, theoretical predictions of r-process abundance patterns still suffer from large uncertainties because experimental nuclear data for neutron-rich nuclei, including atomic masses, $\beta$-decay half-lives, and neutron-capture rates, remain scarce. In particular, the formation mechanism of the rare-earth abundance peak around mass number A ~ 165 has not yet been fully understood, and several mechanisms have been proposed depending on the astrophysical environment. Experimental data for neutron-rich lanthanide nuclei are essential for understanding the formation mechanism of the rare-earth peak.
Among the relevant nuclear properties, atomic masses play a particularly important role because they determine neutron separation energies and reaction Q-values, which strongly affect neutron-capture and $\beta$-decay processes. Even a mass variation of several hundred keV can significantly alter the calculated reaction rates and resulting abundance distributions. Precise mass measurements in the neutron-rich lanthanide region are therefore required to reduce the nuclear-physics uncertainties in r-process calculations.
In this study, we performed precision mass measurements of neutron-rich lanthanide isotopes produced in multinucleon transfer reactions using a $^{136}$Xe beam and a natural Er target at the KEK Isotope Separation System (KISS). The reaction products were collected and transported to a multi-reflection time-of-flight mass spectrograph (MRTOF-MS) for mass determination. In this presentation, we will report the experimental details and the results of the mass measurements.

Speaker: Yuki Yamanouchi (Kyushu University)

6:00 PM Neutron Capture Rate Uncertainties and Their Impact on r-Process Nucleosynthesis

Neutron capture rates play an important role in shaping r-process patterns and are commonly calculated within the Hauser-Feshbach statistical model. Their predictions depend on nuclear masses, nuclear level densities, γ-ray strength functions, and optical potentials. We investigate how uncertainties in these statistical model inputs propagate to r-process nucleosynthesis by calculating neutron capture rates with TALYS and implementing them in the WinNet reaction network for neutron star merger and parametric models. We compare the impact of different nuclear input prescriptions on the final abundance patterns and identify the dominant sources of uncertainty. Among the statistical model ingredients considered, nuclear level densities produce the largest abundance variations. This work provides a systematic assessment of neutron capture rate uncertainties in r-process nucleosynthesis.

Speaker: Mr Yu An (TU Darmstadt, HFHF)

6:00 PM Non-LTE Spectral Constraints on Nucleosynthesis Conditions in Neutron Star Mergers

Radioactive decay in material ejected from a binary neutron star (BNS) merger powers a thermal transient known as a kilonova. Following the detection of the gravitational-wave event GW170817, the associated kilonova AT2017gfo was observed. This event provided the first opportunity for spectroscopic studies of freshly synthesized $r$-process material. Although several absorption and emission features have recently been identified, the elemental abundances inferred from the spectra remain uncertain. The key limitation of previous analyses is the assumption of local thermodynamic equilibrium (LTE), thereby neglecting non-thermal ionization by high-energy electrons from radioactive decay.

We develop a non-LTE ionization model including non-thermal ionization by high-energy electrons to improve abundance estimates for the early-phase spectra of AT2017gfo. Focusing on the prominent absorption feature around $1\,\mu\mathrm{m}$, we investigate the required abundances of helium (He) and strontium (Sr), which have been proposed as the candidate contributors to this feature. Our modeling indicates that the spectral feature requires either He or Sr with a mass fraction of $1\mathrm{-}10\%$ in the ejecta moving at $\sim 0.15\mathrm{c}$. Comparison with nucleosynthesis calculations suggests that the inferred abundances favor relatively neutron-rich conditions ($Y_\mathrm{e} \lesssim 0.35$) for the $r$-process nucleosynthesis in GW170817 because both He and Sr are overproduced at higher electron fractions due to $\alpha$-rich freeze-out. Within this range, there are two regimes: intermediate electron fractions ($0.15 \lesssim Y_\mathrm{e} \lesssim 0.35$) and even lower electron fractions ($Y_\mathrm{e} \lesssim 0.15$). In the former, the inferred Sr abundance is reproduced, in agreement with the solar $r$-process pattern. In the latter, Sr production is suppressed while a sufficient amount of He is produced through $\alpha$-decays of trans-Pb nuclei. Interestingly, if He is the dominant contributor to the absorption feature, this would provide an indirect signature of the production of elements beyond the third $r$-process peak.

Speaker: Koya Chiba (Tohoku University)

6:00 PM Nuclear $\gamma$-ray and Internal-conversion X-ray Emission from Neutron-rich Ejecta Associated with Magnetar Giant Flares

A magnetar is a neutron star whose surface magnetic field is typically stronger than $10^{13}\,{\rm G}$. Its large magnetic energy powers outbursts in the X-ray to $\gamma$-ray bands. The most energetic class of such bursts, with released energies of $10^{44}$--$10^{47}\,{\rm erg}$, is called a giant flare (GF). Radio afterglows detected from two Galactic GFs suggest the presence of massive, fast ejecta with masses of $(10^{-8}$--$10^{-6})\,M_\odot$ and velocities exceeding $0.1c$, where $c$ is the speed of light.
For the Galactic magnetar SGR 1806--20, an enhancement in the MeV $\gamma$-ray band was observed approximately $1000\,{\rm s}$ after the GF. Patel et al. (2025) showed that the observed MeV $\gamma$-ray light curve and spectra can be approximately reproduced by nuclear $\gamma$-ray emission from the radioactive decay of nuclei synthesized in mildly neutron-rich ejecta, assuming an ejecta mass, velocity, and electron fraction of $10^{-6}\,M_\odot$, $0.1c$, and $Y_e=0.4$, respectively.

In this work, we calculate X-ray and $\gamma$-ray light curves and spectra by taking into account nuclear $\gamma$-ray emission and self-absorption in the ejecta, as in Patel et al. (2025). In addition, we include decays through nuclear isomeric states, internal-conversion X-rays (ICX-rays), and composition-dependent opacities, none of which were considered in Patel et al. (2025). Using a spherical, adiabatically expanding, constant-velocity ejecta model coupled to a nuclear reaction network, similar to that of Patel et al. (2025), we evaluate the time evolution of the density, temperature, and abundances of ejecta with a mass of $10^{-6}\,M_\odot$ and a velocity of $0.1c$. We refer to this case as the P25 model. We also consider a heavier and faster ejecta model with a mass of $2\times10^{-5}\,M_\odot$ and a velocity of $0.3c$, motivated by the MHD simulations of Bransgrove et al. (2026). We refer to this case as the B26 model.

We find that, in the P25 model, the light curves and spectra above $200\,{\rm keV}$ are similar to those obtained by Patel et al. (2025). Below $200\,{\rm keV}$, the fluxes are enhanced relative to those of Patel et al. (2025) owing to the effects of nuclear isomers and ICX-rays. Even with the forthcoming COSI mission, the detection of nuclear $\gamma$-rays from a GF in the Large Magellanic Cloud (LMC) at $50\,{\rm kpc}$ would be challenging. ICX-rays in the $20$--$30\,{\rm keV}$ band could be detected with NuSTAR for a nearby Galactic GF within $3\,{\rm kpc}$. In the B26 model, nuclear $\gamma$-rays above $200\,{\rm keV}$ could be detected with COSI even for a GF in the LMC. However, identifying individual nuclear $\gamma$-ray lines would be difficult because of Doppler broadening. For a Galactic GF at $10\,{\rm kpc}$, nuclear $\gamma$-rays and ICX-rays could be detected with NuSTAR in the $30$--$80\,{\rm keV}$, $10$--$30\,{\rm keV}$, and $\lesssim10\,{\rm keV}$ bands at epochs of a few $10^3\,{\rm s}$, $10^4\,{\rm s}$, and a few $10^4\,{\rm s}$ after the GF, respectively.

Speaker: Dr Shin-ichiro Fujimoto (Kumamoto national college of technology)

6:00 PM Nuclear Masses and Isomers in X-ray Burst Nucleosynthesis

Type I X-ray bursts provide an important site for rp-process nucleosynthesis, where reaction flows are strongly influenced by nuclear masses, beta-decay lifetimes, and possible isomeric states. In this talk, I will present recent studies on the impact of new precision mass measurements, including 70Kr near the 68Se waiting point and nuclei in the A～90–100 region, on X-ray burst light curves and final ashes. I will also discuss how low-lying nuclear isomers may modify effective stellar reaction flows and introduce additional uncertainties or pathways in explosive nucleosynthesis.

Speaker: Yudong Luo

6:00 PM Nucleosynthesis in Neutron Star Merger Accretion Disks: Hydrodynamical Heating and Observational Constraints

Simulating nucleosynthesis requires an accurate evolution of temperature and density within astrophysical environments. Contemporary nuclear networks typically post-process tracers from astrophysical simulations and assume the energy generated by nuclear heating is the dominant source of entropy change along the tracer. However, such a procedure neglects entropy changes embedded in the tracer evolution, including those from shocks. Shocks are often found in extreme astrophysical environments, such as NSM accretion disks, which can cause sharp changes in entropy and temperature. As nuclear reactions and thus abundance evolution depend heavily on temperature, neglecting additional changes in temperature will result in inaccurate final abundances, potentially clouding comparisons with observational data. Here, we introduce a temperature-solving routine for the nucleosynthesis code PRISM, which self-consistently computes the temperature due to nuclear heating, shock-heating, and other sources of energy found in Lagrangian tracer particles from simulations. We discuss the impact of this new routine on tracer particles from the 3D GRRMHD NSM accretion disk simulation $\nu$bhlight and compare the abundance pattern changes due to this shock-heating procedure with those due to uncertainties in nuclear data. We additionally discuss how effectively NSM accretion disk abundances map onto metal-poor star observations, such as the well-studied HD222925.

Speaker: Mr Pranav Nalamwar (University of Notre Dame)

6:00 PM Nucleosynthesis in Supernova Remnant Cassiopeia A: Probing Origins of Light Odd-Z Elements and Progenitor Stellar Processes

Chlorine (Cl) and potassium (K) are essential elements for life, yet their cosmic origins remain poorly understood. Current Galactic chemical evolution models underestimate the production of Cl and K by up to an order of magnitude (e.g., Kobayashi et al. 2020). However, these light odd-Z elements have not been clearly detected at their production sites, preventing direct observational tests of their nucleosynthetic origins. Here, we present X-ray observations of the core-collapse supernova remnant Cassiopeia A, led by XRISM/Resolve. For the first time in the X-ray band, we detect Cl and K, together with a possible signature of P, alongside neighboring even-Z elements (XRISM Collaboration 2025). Notably, we measure a K/Ar abundance ratio 1.2–1.3 times the solar value, indicating efficient production of odd-Z elements in this event. Such yields are expected to depend on progenitor properties, including rotation (Limongi et al. 2018), as well as dynamic stellar-evolution processes such as shell mergers (Ritter et al. 2018; Issa et al. 2026). In this presentation, we will present XRISM/Resolve results in combination with complementary observations from previous X-ray missions, and discuss their implications for nucleosynthesis in Cassiopeia A.

Speaker: Kai Matsunaga (Kyoto University)

6:00 PM Origin of the [Na/Mg] Scatter in Metal-poor Stars

Metal-poor stars preserve chemical abundance patterns imprinted by nucleosynthesis in the early Universe, providing key constraints on the evolution and explosions of massive stars at extremely low metallicity. Among these abundance ratios, [Na/Mg] exhibits a particularly large scatter (Ishigaki et al. 2026). Sodium is mainly produced during carbon burning, and its yield can be predicted more robustly than those of later-stage burning products, which are more affected by nonlinear late-stage evolution and supernova explosions. Although previous stellar evolution calculations have shown that sodium yields depend on initial conditions such as the zero-age main-sequence (ZAMS) mass and rotation velocity (Nomoto et al. 2013), the physical origin of the observed [Na/Mg] scatter remains unresolved.

To reveal this origin, we conducted a grid of stellar evolution calculations for massive stars with different ZAMS masses (10, 11, ..., 25 M_sun) and metallicities (10^-2, 10^-3, ..., 10^-5 Z_sun). We investigated how the nuclear burning history is connected to the final yields of carbon-burning products, including Na. We also compiled an observational dataset from two large catalogs of metal-poor stars (Roederer et al. 2014; Cohen et al. 2013), applying selection criteria to reduce uncertainties in stellar populations and abundance measurements, and compared it with our theoretical results.

Our calculations show that the final yields separate into two groups with high and low [Na/Mg] ratios, depending on the burning regime in the O+Ne shell during the final evolutionary stage. Models with stable shell burning retain relatively high [Na/Mg], whereas those experiencing dynamical carbon burning in the O+Ne shell exhibit low [Na/Mg]. In the latter case, alpha-capture reactions, particularly (Na(α,p)Mg) and (Ne(α, γ)Mg), are strongly activated, destroying Na and enhancing Mg production. This reaction pathway explains the observed [Na/Mg] scatter. By contrast, [Al/Mg] does not show a comparable separation, consistent with the observed abundance patterns.

This work identifies the nuclear-reaction origin of the observed [Na/Mg] scatter in metal-poor stars. We discuss its possible connection to shell merger during the final stage of stellar evolution. We also discuss the implication that most stars in our selected observational sample show low [Na/Mg], suggesting that alpha-capture reactions in the O+Ne shell commonly operated in their progenitors. Our findings demonstrate that not only abundance ratios themselves but also their scatter provide important constraints on stellar evolution in the early Universe. Expanding samples of metal-poor stars will therefore be essential for using abundance scatter as a more precise probe of early stellar evolution.

Speaker: Shota Wajima (Kyoto University)

6:00 PM Photoneutron cross sections for 45Sc: Insights into the origin of 45Sc

We report the new measurement of the photoneutron reaction for $^{45}$Sc performed using the quasi-monoenergetic $\gamma$-ray beam at the Shanghai Laser Electron Gamma Source (SLEGS). The obtained cross sections achieve an overall uncertainty better than 4\%. Compared with previous experimental data, the present results are systematically higher by a factor of approximately 1-2. By combining the present data with available $^{44}$Ca($p,\gamma$) reaction data, the parameters of the Hauser-Feshbach statistical model are further constrained. Using the TALYS code, we calculated the relevant reaction rates associated with $^{45}$Sc production channels. The sensitivity of $^{45}$Sc yield was investigated in both $\nu p$-process and O-Ne burning scenarios with respect to the newly determined $^{44}$Sc($n,\gamma$)$^{45}$Sc, $^{44}$Ca($p,\gamma$)$^{45}$Sc, and $^{41}$K($\alpha$,$\gamma$)$^{45}$Sc reaction rates. Our results indicate that the yield of $^{45}$Sc is only weakly affected by the updated nuclear physics inputs, suggesting that nuclear data uncertainties in these channels have a limited impact on the final $^{45}$Sc production in the considered astrophysical environments.

Speaker: Xuan Pang (Beihang University)

6:00 PM Probing proton upscattering of the $^{12}$C Hoyle State with the AToM-X active-target TPC

Proton-induced inelastic scattering to the $^{12}$C Hoyle state (7.654 MeV), which de-excites $^{12}$C to its ground state by carrying away the excitation energy — a process known as "upscattering" — may enhance the stellar triple-alpha process by up to orders of magnitude. The triple-alpha enhancement was predicted using previous measurements of the time-reversed reaction $^{12}$C($p$,$p'$)$^{12}$C$^*$(HS) covering proton energies up to ~2.3 MeV above the Hoyle-state threshold, while the cross section in the higher-energy region relied on Hauser-Feshbach calculations. Using AToM-X, the active-target TPC developed at the Center for Exotic Nuclear Studies (CENS), with 8–18 MeV proton beams, we plan to extend the $^{12}$C($p$,$p'$)3$\alpha$ cross-section measurement up to ~10 MeV above the Hoyle-state threshold and determine the resulting triple-alpha enhancement. A main challenge in this experiment lies in reconstructing the three-alpha events and distinguishing them from background reactions. To address this, we present an analysis using Geant4 simulations to identify the three-alpha tracks.

Speaker: Dr Jung Woo Lee (Center for Exotic Nuclear Studies, Institutes for Basic Science)

6:00 PM Recoil-enabled neutrino heating in core-collapse supernovae

In core-collapse supernova explosions, the energy transfer from neutrinos to matter (neutrino heating) is considered a key ingredient of the explosion mechanism. However, even after taking into account multidimensional hydrodynamics, magnetic fields, turbulence, and realistic nuclear equations of state, reproducing robust explosions over a wide range of progenitors remains challenging.
Janka and Müller showed that even a modest increase in neutrino heating efficiency can significantly enhance the explosion energy [1]. This suggests that relatively small corrections to neutrino energy deposition may have important consequences for the explosion dynamics. In our previous study, we investigated the energy and momentum transfer through elastic neutrino scattering with nucleons, nuclei, electrons, and bulk nuclear matter, and suggested that these processes may provide an additional heating source of the magnitude required for successful explosions [2].
In the present study, the recoil-induced energy transfer is reevaluated systematically using the dynamic structure factor of the medium. Quantitative contributions from coherent elastic neutrino–nucleus scattering (CEvNS), neutrino–electron scattering, and other elastic scattering processes to neutrino heating will be discussed.
[1] H.-T. Janka and E. Müller, Astron. Astrophys. 306 (1996) 167–198.
[2] T. Shima, Phys. Lett. B872 (2026) 140135

Speaker: Tatsushi Shima (Research Center for Nuclear Physics, Osaka University)

6:00 PM Relativistic Quantum Description of Synchrotron Radiation from Ultra-High-Energy Protons in Strong Magnetic Fields

The origin of ultra-high-energy cosmic rays (UHECRs), such as the recent $2.44×10^{20}$ eV "Amaterasu" event detected by the Telescope Array, remains one of the most intriguing mysteries in astrophysics. Identifying the sources of these particles is challenging because their trajectories are significantly deflected by cosmic magnetic fields. A promising approach to identifying UHECR sources is the observation of synchrotron γ-rays emitted by UHE protons in extremely strong magnetic fields ($B \gtrsim 10^{15}$ G), such as those associated with magnetars.
In this presentation, we propose a comprehensive theoretical framework for describing synchrotron emission from UHE protons in the intense magnetic field regime. Unlike conventional semiclassical approaches, our model is based on a fully relativistic quantum treatment using the Dirac equation, where the motion of particles is quantized into discrete Landau levels. In the UHE regime, the emission processes are not limited to electromagnetic γ-rays; strong-interaction particle production, including π and ρ mesons, becomes significant. Our formulation consistently incorporates these processes alongside proton recoil effects.
A significant computational challenge arises because the Landau quantum numbers for UHE protons can reach $N≳10^{15}$, rendering direct numerical calculations impractical. We overcome this difficulty by identifying and applying a generalized scaling rule for quantum transition probabilities. This rule allows us to reliably infer results for extremely large Landau numbers from calculations performed at lower, manageable values.
Our results reveal that proton recoil significantly modifies emission behavior. Specifically, we find that the decay width reaches a maximum and subsequently decreases with increasing magnetic field strength—a stark contrast to the monotonic increase predicted by classical theory. This work provides a rigorous theoretical foundation for interpreting high-energy radiation from UHECR acceleration sites and offers new insights into the nature of the most energetic particles in the universe.
References
[1] Telescope Array Collaboration, Science 382, 903 (2023).
[2] A. Tokuhisa and T. Kajino, ApJ. 525, L117 (1999).
[3] T. Maruyama et al., Phys. Rev. D113, 023023 (2026)..

Speaker: Tomoyuki Maruyama (College of Bioresource Sciences, Nihon University)

6:00 PM Revealing α-Element's Past with Subaru/IRD: Oxygen Abundance of 35 Very Metal-Poor Stars from Near-IR OH lines

Oxygen abundances in very and extremely metal-poor (V/EMP) stars provide critical constraints on early massive stars' nucleosynthesis. We present an oxygen abundance analysis for 35 V/EMP stars ($-4.0<\text{[Fe/H]}<-1.5$) using near-infrared $H$-band OH lines from high-resolution Subaru/IRD spectra. To evaluate these atmospheric diagnostics, we compare OH-based abundances against the 3D/NLTE-insensitive [OI] 6300Å line using archival optical spectra. Oxygen abundances are determined via 1D/LTE spectral synthesis.

We identify a strong temperature-dependent discrepancy between the tracers. In cooler red giants ($T_\text{eff}\lesssim4600$K), OH-based abundances are systematically lower than [OI] by 0.05-0.25 dex, while warmer RGs show a higher one, directly consistent with expected 3D atmospheric effects on molecular lines in general. Despite this systematic offset, thanks to numerous near-IR OH lines yields significantly smaller random errors than relying on a single, weak [OI] line.

Leveraging this statistical precision, we derive an empirical calibration to align our more precise 1D/LTE OH-based abundances onto the robust [OI]-based abundance. This correction is not equivalent to canonical 3D/NLTE OH-based abundances, but it substantially reduces scatter in the [O/Fe] trend, bringing our OH-based abundances into better agreement with Galactic chemical evolution models. Additionally, we are ready to extend this study to even lower metallicity RGs with future NIR high-resolution spectroscopic observations.

Speaker: Bakuh Danang Setyo Budi (SOKENDAI/NAOJ)

6:00 PM Rotation-induced Relaxation of Supernova Constraints on Axionlike Particles

Supernovae realize extreme environments of high temperature and high density, serving as useful astrophysical laboratories for probing feebly interacting new particles such as axion-like particles (ALPs). In this work (arXiv:2604.17840 [astro-ph.HE]), we investigate how rotation modifies the constraints on MeV-scale ALPs coupled to photons derived from SN 1987A. We constrain the ALP parameter space based on both the energy-loss argument and the gamma-ray limits. Adopting initial angular velocities of $\Omega_0 = 0.0$ and $1.0~\mathrm{rad\,s^{-1}}$ in the iron core, we carry out two-dimensional core-collapse supernova simulations for three progenitor models --- a $14 + 9\,\mathrm{M}_\odot$ binary system and $13\,\mathrm{M}_\odot$ and $18\,\mathrm{M}_\odot$ single stars with solar metallicity --- and estimate ALP emission rates through post-processing. We find that rotation suppresses ALP emission by reducing the core temperature via centrifugal support. The neutrino luminosity is similarly reduced by rotation; however, the suppression of ALP emission is more pronounced, resulting in relaxed constraints under a simplified criterion based on the energy-loss argument. This effect is particularly significant in the rotating $18\,\mathrm{M}_\odot$ model, where a substantial decrease in the central temperature occurs at post-bounce time $t_{\mathrm{pb}} = 0.8$-$1~\mathrm{s}$. For this simplified criterion, such rapid temporal variations indicate that the resulting constraints depend sensitively on both the evaluation time and the underlying supernova model. In this talk, we also discuss the impact of ALP energy transport on the thermodynamic evolution of the SN ejecta and its effects on nucleosynthesis.

Speaker: Tsurugi Takata (Fukuoka University)

6:00 PM Secondary i- and s-Processes Following the r-Process in Collapsar Jets

The origin of heavy elements via the r-process remains a frontier in nuclear astrophysics. While neutron star mergers (NSMs) are confirmed sites, collapsars and magnetohydrodynamically driven jets (MHDJs) offer unique environments due to their distinct jet dynamics.
We discover for the first time that fission neutrons released after the r-process freeze-out can induce secondary i- and s-processes exclusively in collapsar jets. This originates from the synergy of an extremely neutron-rich environment and jet deceleration, which maintains the required late-time neutron density. To quantify these contributions, we propose a new theoretical decomposition method to separate the contributions of r-, i-, and s-processes. Sensitivity analyses reveal that specific neutron-capture reactions, such as Yb175(n,g)Yb176 and Er169(n,g)Er170, significantly impact rare-earth element synthesis, pointing to future experimental targets. Additionally, elevated [Tm/Eu] and [Lu/Eu] ratios are identified as potential observational indicators for collapsars.
Furthermore, we establish a theoretical framework for late-time jet propagation by considering the collision between the jets and the ambient medium, deriving a density evolution corrected for jet deceleration and mass accumulation. This work bridges hydrodynamic simulations, nuclear physics, and astronomical observations, enriching our understanding of heavy element nucleosynthesis.

Speaker: Zhenyu He (China Institutu of Atomic Energy)

6:00 PM Stellar 191Ir(n, g) cross section: calculations and astrophysical s-process nucleosynthesis implications

Neutron-capture cross sections are essential nuclear physics inputs for modeling the s-process nucleosynthesis, which is responsible for producing approximately half of the elements heavier than iron in the Universe. The isotope {}^{191}_{77}\mathrm{Ir} plays an important role in the s-process because neutron capture on $^{191}\mathrm{Ir}$ produces $^{192}\mathrm{Ir}$, a branching-point nucleus that influences the nucleosynthesis flow in the iridium-platinum-osmium mass region. However, existing experimental measurements and evaluated nuclear data libraries for the {}^{191}\mathrm{Ir}(n,\gamma){}^{192}\mathrm{Ir} reaction show significant discrepancies, leading to uncertainties in astrophysical reaction rates and abundance predictions. In this work, the neutron-capture cross section of the {}^{191}\mathrm{Ir}(n,\gamma){}^{192}\mathrm{Ir} reaction was investigated using theoretical calculations. Calculations were performed using the TALYS-2.2 nuclear reaction code with six different nuclear level density models. The calculated cross sections were validated against experimental data available in the EXFOR database and compared with the latest version of the evaluated nuclear data libraries ENDF/B-VIII.1, JEFF-4.0, JENDL-5, TENDL-2025, and BROND-3.1. The results indicate that the microscopic Skyrme-Hartree-Fock-Bogoliubov (SHFB) and Gogny-Hartree-Fock-Bogoliubov (GHFB) level density models provide the best agreement with experimental observations. MACSs and stellar reaction rates were determined for the astrophysically relevant temperature range of $kT = 5$--$100\,\mathrm{keV}$. The derived reaction rates are systematically lower than the recommended KADoNiS 0.3 values. Implementation of the new MACSs in the NETZ s-process network calculations shows an increase of approximately 5.2\% in the final abundance of 191Ir during He-shell flash conditions in thermally pulsing asymptotic giant branch (TP-AGB) stars. These results provide improved nuclear data for {}^{191}\mathrm{Ir} and contribute to a more reliable understanding of heavy-element nucleosynthesis in stellar environments.

Speaker: Prof. Kawchar Patwary (Comilla University)

6:00 PM Study of feasibility of the $^{84}$Kr(n,$\gamma$) $^{85}$Kr reaction measurement via the Asymptotic Normalization Coefficient method for for Astrophysical s-process

The neutron-capture reaction $^{84}$Kr(n,$\gamma$)$^{85}$Kr plays an important role in the astrophysical s-process, where $^{85}$Kr acts as a key branching-point nucleus influencing the production of isotopes in the mass region around Sr and Rb. Since direct measurements of this reaction are experimentally difficult, an indirect approach based on the Asymptotic Normalization Coefficient (ANC) method is proposed to constrain the direct neutron-capture at astrophysical energies. The feasibility study of the reaction $^{84}Kr(d,p)${85}Kr measurements will be presented through reaction kinematics and detector response simulations to identify the most favorable setup.

Speaker: Prof. Rosario Gianluca Pizzone (Università di Catania & INFN-LNS)

6:00 PM Study of Low-Lying Negative-Parity T=5 States in 48Ca with ANASEN and a Reaccelerated 47K Beam

Particle-hole excitations near closed nuclear shells provide important information on single-particle properties, shell evolution, and residual two-body interactions. While doubly magic and near-doubly magic nuclei have been extensively studied, charge-changing particle-hole excitation states in $^{48}$Ca, corresponding to negative-parity T=5 states, remain less well established. These states are of particular interest because they can be interpreted as isobaric analog states associated with particle-hole excitations in $^{48}$K.
To investigate these states, the $^{47}$K($p$,$p$)$^{47}$K elastic resonance scattering measurement was performed in inverse kinematics using the Array for Nuclear Astrophysics and Structure with Exotic Nuclei (ANASEN) as an active-target detector. A radioactive $^{47}$K beam from ReA3 at the National Superconducting Cyclotron Laboratory, with an energy of 4.6 MeV/u, was delivered to methane gas inside ANASEN. The methane gas served as both the hydrogen target and the active detector medium, allowing the excitation function for $p$+$^{47}$K elastic scattering to be measured over $E_{c.m.}$ = 1-4.5 MeV.
Recoil protons were detected with the ANASEN charged-particle detector system, and the reaction kinematics were reconstructed to obtain the center-of-mass excitation function. The excitation function is being analyzed to extract resonance parameters for negative-parity T=5 states in $^{48}$Ca. The experimental method, analysis procedure, and preliminary results will be presented.

Speaker: Gyoungmo Gu (Sungkyunkwan University,Center for Exotic Nuclear Studies, Institute for Basic Science)

6:00 PM The challenging direct determination of the cross section of the 12C+12C reaction at LUNA

Carbon burning is a crucial stage of stellar evolution, determining whether stars evolve toward neutron stars, black holes, or CO white dwarfs. These outcomes depend strongly on the $^{12}C+^{12}C$ reaction rate, which is still uncertain at astrophysical energies.

This reaction mainly proceeds through the $^{12}C(^{12}C,\alpha)^{20}Ne$ and $^{12}C(^{12}C,p)^{23}Na$ channels. While it has been studied over a wide energy range, direct measurements only reach 2.1 MeV, above the astrophysical region. Indirect methods extend to lower energies, but with significant normalization uncertainties, making new direct measurements essential.

A direct study is now being carried out by the LUNA collaboration at LNGS using high-intensity carbon beams and a low-background $\gamma$-detection setup based on a 150% HPGe detector surrounded by NaI scintillators. This configuration combines high efficiency, excellent resolution, and strong background suppression, providing a sensitivity much higher than previous direct experiments.

Besides improving the measurement of the $^{12}C+^{12}C$ cross section, this setup will also allow the study of the level density and possible cluster structure of $^{24}Mg$ in the $E_{cm}=1.5–3.5$ MeV region, which may play an important role in the astrophysical reaction rate.

In this contribution, I will present the recent progress in setup development and installation, Geant4 simulations, HPGe detector characterization, and the first beam-on-target results for the direct study of the $^{12}C+^{12}C$ reaction.

Speaker: Riccardo Maria Gesuè (Gran Sasso Science Institute (GSSI), INFN LNGS)

6:00 PM The Impact of Residual Heating on Type-I Bursts

In accreting neutron stars, rapidly brightening phenomena have often been observed, so-called Type-I bursts. Most of them are observed in a hard state, that is, a relatively dark phase. In the hard state, most observations show an inverse relation between burst recurrence time and accretion rate, which is in line with conventional burst models.

Recently, many bursters have been observed when they transit accretion regime from soft state to hard state, the former of which shows brighter persistently. In this case, burst observations tend to show a shorter burst recurrence time than that expected from the inverse relation, implying a new physical mechanism beyond conventional burst models.

As one of the solutions to resolve such a recurrence-time anomaly, we propose the contribution of residual heating, the excess heat inside the accreting neutron star crust in the past soft state. Although most previous burst models follow the thermal evolution of only the bursting atmosphere, to consider the effect of residual heating, one should follow whole neutron-star cooling in Type-I burst simulations. We perform burst simulations in accreting neutron stars that simultaneously cool due to thermal emission, with different cooling timescales and accretion rates in the soft state. We also argue whether the recurrence time anomaly could be solved in some latest observations.

Speaker: Dr Akira Dohi (RIKEN)

6:00 PM Theoretical study of momentum coverage and energy normalization in the $^{13}\mathrm{C}$ neutron-spectator THM approach to $^{12}\mathrm{C}+^{12}\mathrm{C}$ fusion

We investigate the $^{13}\mathrm{C}(^{12}\mathrm{C},n)^{24}\mathrm{Mg}^*$ reaction as a neutron-spectator Trojan Horse Method (THM) route to low-energy $^{12}\mathrm{C}+{}^{12}\mathrm{C}$ fusion, using the physical $^{13}\mathrm{C}=^{12}\mathrm{C}+n$ $p_{1/2}$ overlap. For a 27 MeV $^{12}\mathrm{C}$ beam and $0.8\leq E_{CC}\leq2.7$ MeV, the momentum-volume density peaks at $72.5$ MeV/$c$, with half-height points at $32.4$ and $136.4$ MeV/$c$. At $E_{CC}=1.5$ MeV, the full neutron angular range samples only $85.7$–$148.4$ MeV/$c$. Thus, no fixed-energy angular trajectory covers both intrinsic half-height points, and agreement with an accessible momentum profile alone does not determine the transfer normalization.

We also examine the energy-dependent distorted-wave correction relevant to THM strength extraction. At $E_{CC}=0.8$ MeV and a neutron center-of-mass angle of $15^\circ$, the factorized $^{13}\mathrm{C}$ corrections are $R_S=1.123$ for Coulomb distortion and $1.693$ with the I0/KD optical input, compared with $\sim4.0\times10^{-3}$ and $2.3\times10^{-3}$ for the converted published $^{14}\mathrm{N}$ results. Direct integration of the displaced waves changes these values to $0.421$ and $0.551$, respectively, showing that the surface factorization can change both the magnitude and the direction of the inferred energy correction. These results show that momentum-shape tests and energy normalization need to be treated separately in quantitative THM analyses.

Speaker: Dr Zifeng Luo (Institute for Basic Science)

6:00 PM Ti isotopic analysis of presolar SiC using laser post-ionization SNMS

Primitive meteorites contain nanometer- to micrometer-sized grains that exhibit isotopic anomalies in various elements relative to the solar system composition. These grains, known as presolar grains, preserve isotopic signatures that reflect nucleosynthesis in the stellar sources before the formation of the solar system. High-precision trace element isotopic analyses of presolar grains provide such information, allowing comparisons with predictions from nuclear physics and stellar evolution models. Among the presolar grains, presolar SiC grains have been extensively studied because they are relatively abundant in meteorites, and well-established methods exist for their isolation. However, because of their small size, high spatial resolution is required to analyze individual grains. In addition, high sensitivity is needed to obtain sufficient precision. Therefore, in this study, we employ a laser post-ionization secondary neutral mass spectrometer (SNMS) developed at the University of Osaka. The high spatial resolution of the Ga ion beam and the high ion yield achieved by laser post-ionization make this technique promising for isotopic analysis of presolar SiC. A multi-turn time-of-flight mass spectrometer (MULTUM) is used for mass separation, providing high mass-resolving power by adjusting the number of cycles.
In this study, we focused on Ti, a relatively abundant trace element in presolar SiC. Through instrument optimization and improvement of the measurement conditions, we successfully performed Ti isotopic analyses of presolar SiC. Ti isotopic anomalies were detected, and the observed isotopic patterns demonstrated precision comparable to that of previous studies. In the future, we plan to extend the method to simultaneous analyses of Ti and heavy elements, providing stronger constraints on the physical conditions of the parent stars.

Speaker: Kei Sato (The University of Osaka)

6:00 PM Toward a Comprehensive Understanding of Big Bang Nucleosynthesis

The aim of our research is to achieve a comprehensive understanding of the Big Bang Nucleosynthesis (BBN) process and to potentially resolve the Cosmological Lithium Problem (CLP). The CLP is a well-known issue in astrophysics, referring to the overestimation of the primordial $^7\mathrm{Li}$ abundance in standard BBN models compared to astronomical observations. One of the major challenges in addressing this problem is that many of the nuclear reaction cross sections relevant to BBN have not been measured over the full BBN energy range. Addressing this limitation requires a combination of experimental measurements and theoretical modeling to provide reliable cross sections for BBN calculations.
Our research employs both experimental and theoretical approaches to address the CLP: high-precision measurements of key nuclear reaction cross sections and the re-evaluation of nuclear reactions used in BBN calculations, including investigations of possible resonant contributions through flexible cross-section parametrizations.
In this study, we present the results of our previous experimental study and discuss a future theoretical approach.
The experimental approach focuses on measuring the cross section of the $^7\mathrm{Be}(d,p)^8\mathrm{Be}$ reaction, motivated by theoretical suggestions of its important role in the destruction of $^7\mathrm{Be}$ during BBN [1]. We produced a radioactive $^7\mathrm{Be}$ target and measured the $^7\mathrm{Be}(d,p)^8\mathrm{Be}$ reaction cross section at the tandem facility of Kobe University in Japan. The cross section at the lowest energy of $E_{\mathrm{c.m.}} = 0.12$ MeV was measured with the highest sensitivity achieved in previous measurements [2,3,4]. The measured $^7\mathrm{Be}(d,p)^8\mathrm{Be}$ cross sections indicate a modest impact on the CLP.
A future theoretical study is outlined, focusing on the exploration of potential resonant contributions in key nuclear reactions. In this approach, nuclear reaction cross sections are parametrized using an external functional form, enabling a flexible inclusion of resonant contributions within the BBN reaction network. This allows us to investigate whether such resonant effects could modify reaction rates relevant to BBN and thereby provide further insight into the CLP.

References
[1] S. Q. Hou et al., Phys. Rev. C 91, 055802 (2015).
[2] R. Kavanagh, Nucl. Phys. 18, 492--501 (1960).
[3] C. Angulo et al., ApJ 630, L105 (2005).
[4] N. Rijal et al., Phys. Rev. Lett. 122, 182701 (2019).

Speaker: Azusa Inoue

6:00 PM Understanding the actinide production through the Th/Eu abundance ratio

While the r-process yield, especially the actinide-to-lanthanide abundance ratio, has been widely studied in metal-poor stars, their evolution in the metal-rich regime is poorly understood. One cause is the limited Th abundance measurement due to the difficulty of detecting the commonly used Th II 4019 Å absorption line in stellar spectra.
In this study, we present the [Th/Eu] ratio measurement for a sample of metal-rich disk stars. Our sample covers 89 giants with metallicities -0.7 < [Fe/H] < 0.4 and ages from a few hundred Myr to ~ 14 Gyr. Age information from stellar seismology is essential for studying the radioactive element Th, as it allows us to correct for decay and recover the initial production ratios. We derive Th and Eu abundances through spectral fitting of high-resolution spectra (R~80,000) obtained with the High Dispersion Spectrograph (HDS) at the Subaru Telescope. We also demonstrate the viability of using the less-studied Th II 5989 Å line to measure Th abundance, opening the possibility of extending such measurements to larger stellar samples.
We find no correlation between [Th/Eu] and [Fe/H], which indicates a stable [Th/Eu] production ratio across metallicities. On the other hand, our study shows, for the first time, a correlation between the [Th/Eu] production ratio and stellar age, with older stars showing a higher ratio than younger stars. This hints at the different contributions of short- and long-timescale sources in the early universe and the present day. Our results imply the presence of a short-timescale source(s) that can produce a high actinide-to-lanthanide ratio, which requires further investigations from the theoretical side. This work provides observational constraints to better understand the astrophysical origins of the r-process in the context of Galactic chemical evolution.
We will further explore our findings by analyzing stars with more accurate age measurements, i.e., those belonging to stellar clusters. We are currently working on a sample of giant stars in open and globular clusters, covering young and old populations, for which high-resolution spectra are available from the Gaia-ESO Survey. We expect to confirm the [Th/Eu]-age trend by analyzing this sample and further establishing our Th line analysis method for a larger sample of metal-rich stars.

Speaker: Ainun-Nahdhia Azhari

6:00 PM Validity test of 20Ne as a Trojan Horse nucleus toward the measurement of the 16O+16O fusion cross section

Our recent work [1] investigates the 16O+16O fusion reaction, a critical process for understanding how massive stars burn oxygen during their final evolutionary stages. Because direct measurements at low stellar energies are difficult to obtain, researchers performed a validity test using the Trojan Horse Method to study the reaction indirectly. The study specifically explores using 20Ne as a Trojan Horse nucleus, examining its internal alpha-particle and 16O cluster structure to act as a virtual source for the fusion. Experimental data gathered from laboratories in Poland and Kazakhstan were compared against theoretical simulations involving relativistic mean-field models. The results show a fair agreement between the measured reaction yields and predictions, confirming that 20Ne is a viable tool for future nuclear astrophysics research. This successful test paves the way for more precise independent measurements of fusion cross sections that occur deep within stellar interiors.

[1] S. Hayakawa, S. Typel, M. La Cognata, et al., "Validity test of 20Ne as a Trojan Horse nucleus toward the measurement of the 16O+16O fusion cross section", Eur. Phys. J. A (2026) 62:13.

Speaker: marco la cognata (infn-lns)

6:00 PM Waiting for T CrB: A Once-in-a-Lifetime Opportunity to Catch Nova Neutrinos

The detection of near-TeV gamma rays from the 2021 outburst of RS Oph ($2.45$ kpc) by MAGIC established recurrent novae as Galactic TeV particle accelerators. However, the underlying emission mechanism—hadronic or leptonic—remains unresolved due to the absence of coincident neutrino detections. The anticipated outburst of the much closer recurrent nova T Coronae Borealis (T CrB, $\sim0.887$ kpc) provides an exceptional opportunity to probe the hadronic origin of nova emission through neutrino observations. We present the first comparative study of the secondary gamma-ray and neutrino emission expected from the forthcoming T CrB outburst by considering two proton acceleration scenarios: (i) external shocks (ES) at $\sim10^{13}$ cm and (ii) magnetic reconnection (MR) near the white dwarf surface at $\sim10^{9}$ cm. While the benchmark ES scenario predicts TeV gamma-ray emission detectable by current observatories, its associated neutrino flux remains below the sensitivity of existing neutrino telescopes. In contrast, the MR scenario produces a detectable neutrino signal within the reach of IceCube and KM3NeT, while the accompanying gamma rays are efficiently absorbed in the dense nova environment. Consequently, the MR neutrinos are expected to arrive several hours before the onset of ES-generated gamma-ray and neutrino emission, providing a distinctive temporal signature to discriminate between the underlying particle acceleration mechanisms in recurrent novae.

Speaker: Prantik Sarmah (Institute of High Energy Physics, Beijing)

6:00 PM Weak rates of nuclear Urca pairs in $sd$- and $pf$-shell nuclei relevant to Urca processes in the neutron star ocean

Nuclear Urca processes play important roles in the cooling of stars. Electron-capture and $\beta$- decay rates of the nuclear pairs, $^{25}$Mg-$^{25}$Na and $^{23}$Na-$^{23}$Ne, were evaluated by the shell model, and successfully applied to the cooling of O-Ne-Mg cores of stars with M$_{\odot}$ [1]. The Urca processes were shown to induce the cooling of neutron star (NS) crusts [2], where the weak rates were evaluated using the QRPA. The shell model was used to evaluate the weak rates of the $^{31}$Al-$^{31}$Mg pair [3-5], which is important for the cooling of NS crusts.
Recently, an indication of the possible existence of nuclear Urca processes in the NS ocean was obtained from the observation of superburst MAXI J1752-457 [6]. Here, we evaluate the weak rates of Urca pairs in the $sd$- and $pf$-shells, relevant to the cooling of the NS ocean [2,7] by the shell model in stellar environments, including screening effects. The nuclear pairs with $A$ =25 and 23 in the $sd$-shell are evaluated with the USDB [8], while those in the $pf$-shell, $^{57}$Mn-$^{57}$Cr, $^{63}$Ni$^{\ast}$-$^{63}$Co, $^{57}$Fe$^{\ast}$-$^{57}$Mn, $^{55}$Mn-$^{55}$Cr, $^{65}$Cu-$^{65}$Ni, $^{49}$Ti-$^{49}$Sc, and $^{67}$Cu-$^{67}$Ni, are evaluated with the GXPF1J [9]. Experimental B(GT) and energies are used as far as they are available.
The cooling strengths, L$_{34}$, [4,5,7] are evaluated by taking into account the calculated and experimental rates and energies, effective Q values obtained with the inclusion of the screening effects, and Coulomb distortion corrections. While dominant contributions to L$_{34}$ come from transitions between the ground states, when the g.s. to g.s. transition is forbidden, the contribution from the transition from (to) excited states becomes important. L$_{34}$ values increase with temperature due to contributions from transitions involving excited states. When there are forbidden transitions between low-lying states with low excitation energies, L$_{34}$ decreases. Compared to the estimates in Ref. [7], the L$_{34}$ values are found to be enhanced by a few to several times. A comparison of the L$_{34}$ values for the $^{25}$Mg-$^{25}$Na pair is also made to those in Ref. [5]. An evaluation of L$_{34}$ for the nuclear pairs in the $pfg$-shell, $^{69}$Zn-$^{69}$Cu, $^{73}$Ga-$^{73}$Zn, $^{79}$As-$^{79}$Ge, $^{81}$Se-$^{81}$As, and $^{81}$Br-$^{81}$Se, is now under way.

[1] H. Toki, T. Suzuki, K. Nomoto, S. Jones, and R. Hirschi. PRC 88, 015806 (2013);
T. Suzuki, H. Toki, and K. Nomoto, Astrophys. J. 817, 163 (2016).
[2] H. Schatz et al., Nature 505, 62 (2014).
[3] T. Suzuki and N. Shimizu, Frontiers in Physics 12, 1434598 (2024).
[4] S. Sharma, P. C. Srivastava, and T. Suzuki, Phys. Rev. C 112, 015806 (2025).
[5] L. J. Wang et al., Phys. Rev. Lett. 127, 172702 (2021).
[6] H. Huang, A. Dohi, A. Aoyama, T. Takeda, and N. Nishimura, arXiv:2602.19018 (2026).
[7] A. Deibel, Z. Meisel, H. Schatz, E. F. Brown, and A. Cumming, Astrophys. J. 831, 13 (2016).
[8] W. A. Richter, S. S. Mkhize and B. A. Brown, Phys. Rev. C 78, 064302 (2008).
[9] M. Honma, T. Otsuka, T. Mizusaki, M. Hjorth-Jensen, and B. A. Brown, J. Phys.: Conf. Ser. 20, 7 (2005); M. Honma et al., Phys. Rev. C 65, 061301(R) (2002); 69, 034335 (2004).

Speaker: Prof. Toshio Suzuki (Nihon University)

6:00 PM When AI is wrong: Apply non-artificial intelligence. How to determine model errors and fission-barriers

To discuss the determination of model errors we use for simplicity mass models ("mass tables"). Usually their errors are characterized by the root-mean-square deviation $ \sigma_{\mathrm{rms}} = \left( \left[ \sum_{i = 1}^n \left( M_{\mathrm{exp}}^i - M_{\mathrm{th}}^i \right)^2 \right] / n \right)^{1/2} $. However, we immediately (should) see
that the experimental error contributes to the rms value so it is an overestimate of the model error. What to do? We asked AI and the first suggestion that came up was: Multiply each squared residual by a weight $ w_i = 1/ \sigma_{\mathrm{exp}}^2 $ where $ \sigma_{\mathrm{exp}}^2 $ is the standard deviation for that point. But when applied to masses and especially in fitting model parameters then data points with tiny experimental errors would completely determine the outcome, which obviously is not what we want. Actually the mass of $ {}^{12} \mathrm{C} $ has zero error because it defines the atomic mass unit!! The failure of AI shows it is not optimum to hunt for some expression to use, instead we must apply real intelligence. A first step is to figure out what a model error really is. If you have a lot of model data points they usually follow a Gaussian distribution around the correct value. So, what we like to determine is the σ of this distribution. This is accomplished by applying the maximum likelihood method, and was presented already 40 years ago in [1], but few use it. I will apply it to some older and more current mass models and discuss how they perform for data that was not known when they were published. Another misconception that persists in the community is that constrained HFB calculations "automatically" converge towards fission barrier saddle points and that it is not necessary to calculate the energy versus many shape degrees of freedom. For example [2] states They require only one constraint to force a stretching of the system along the various stages while all other details of the rearrangements and shapes result automatically of the calculation. It is true that a curve is obtained but it is often not related to the actual fission barrier [3].

References
[1] P. Möller and J. R. Nix, Atomic Data Nucl. Data Tables 39 (1988) 213, and LosAlamos preprint LA-UR-3983 (with more complete tables).
[2] J. Erler, K. Langanke, H.P. Loens, G. Martinez-Pinedo, and P.-G. Reinhard, Phys. Rev. C 85 024802 (2012).
[3] P. Möller, A. J. Sierk, R. Bengtsson, H. Sagawa, and T. Ichikawa, Phys. Rev. Lett. 103 (2009) 212501.

Speaker: Peter Moller (Lund University)

Thu, October 22

9:00 AM → 9:30 AM Morning Coffee

9:30 AM → 10:50 AM Scientific Session: Session 9

9:30 AM Nuclear theory for neutron-star matter and pairing

After a brief overview of modern nuclear theory (covering both ab initio and phenomenological techniques), this talk will address a number of our recent works on many-nucleon systems. One such line of research involves the propagation of theoretical uncertainties from the chiral nuclear
interaction all the way to the few- and many-nucleon level, using quantum Monte Carlo and efficient emulators. Another family of works addresses the novel statistical technique known as conformal prediction, which we were the first to apply to nuclear physics and have recently extended to neutron-star equations of state. Finally, time permitting, I will also discuss our ongoing studies on pairing in heavy nuclei.

Speaker: Prof. Alex Gezerlis (University of Guelph)

9:55 AM Mass Measurement of New Neutron-Rich Americium Isotopes

The neutron-rich, lighter actinoid isotopes are important for revealing the origin of the heavy r-process elements beyond Pb, such as uranium. In the recent observations, the r-process element was identified in the kilonova AT2017fgo associated with the neutron-star merger. Moreover, the theoretical study has shown that the radioactive isotopes produced by the r-process play an important role as a heating source for the kilonova’s ejecta. Theoretical investigations indicate that energy release via the spontaneous fission of 254Cf is dominant among them.
The abundance of 254Cf produced in the r-process nucleosynthesis strongly depends on the nuclear masses of the neutron-rich isotopes along the predicted r-process path. However, the location of the predicted r-process path is far from the β-stable line, and the variance of theoretically predicted masses becomes larger toward the neutron-rich region, where experimental information is lacking. In particular, the difference in the nuclear mass model significantly changes the predicted kilonova light curve. Therefore, comprehensive mass measurements of the neutron-rich trans-Pb isotopes are required. However, the neutron-rich actinoid region had long been unexplored territory due to the difficulties with production methods.
Multinucleon transfer (MNT) reactions have recently been discussed as a new method to access the unreached neutron-rich region. In this presentation, we report mass measurements of new neutron-rich americium isotopes produced via the MNT reaction with 248Cm, as the first step toward exploring the Terra Incognita of the nuclear chart.

Speaker: Dr Sota KIMURA (KEK)

10:15 AM Systematics of fission-fragment mass distributions and pre- and prompt-neutron emission in neutron-rich U isotopes

A quantitative understanding of nuclear fission is important in nuclear physics, astrophysics, and nuclear applications. However, its full physical description remains unresolved because fission is a complex multistage process. We investigate the fission properties of neutron-rich uranium isotopes relevant to r-process nucleosynthesis, focusing on fragment mass distributions and prompt neutron emission in the postfission stage, while also discussing the role of multi-chance fission and prefission neutron emission. We employ a hybrid framework [1], in which fission dynamics are described by a Langevin approach and prompt neutron emission is treated with a Hauser-Feshbach statistical model code, CCONE [2]. In the Langevin calculation, the neck parameter $\varepsilon$ is introduced as an adjustable quantity, and we examine how different treatments of $\varepsilon$ affect the predicted observables. We calculated uranium isotopes from ${}^{245}$U to ${}^{276}$U, covering a wide neutron-rich region relevant to the r-process. We find a transition from asymmetric to symmetric fission around $A \sim 250$, although the detailed behavior depends on the choice of $\varepsilon$. The prompt neutron multiplicity generally increases toward heavier isotopes, but this trend is modified by changes in the fission asymmetry. We also discuss how multi-chance fission influences the fragment mass distributions and neutron emission in the most neutron-rich isotopes. Variations in $\varepsilon$ also affect neutron emission, although the resulting uncertainty remains at the level of about 10% within a reasonable parameter range. Our results provide a systematic dynamical description of fragment mass distributions and prompt neutron emission for neutron-rich uranium isotopes and show that the evolution of the fission mode plays a key role in determining postfission neutron emission.

[1] S. Tanaka, N. Nishimura, F. Minato, and Y. Aritomo, Phys. Rev. C 108, 054607 (2023).
[2] O. Iwamoto, N. Iwamoto, S. Kunieda, F. Minato, and K. Shibata, Nuclear Data Sheets, 131:259--288 (2016).

Speaker: Dr Nobuya Nishimura (Kogakuin University)

10:35 AM High-precision mass measurements for improving the r-process simulations

Approximately half of the nuclei heavier than iron are produced by the rapid neutron-capture process (r process). The r process nucleosynthesis can be simulated with nuclear reaction network codes for which nuclear data input is important. In particular, neutron-capture and photodisintegration rates are essential as they directly affect the outcome of the simulations. One of the key factors that affect the neutron capture rates are nuclear masses. However, many neutron-rich nuclei have rather large mass uncertainties. By enhancing the precision of the poorly known masses, we can also obtain more precise reaction rates which in turn lead to reduced uncertainties in the r-process simulations. This helps us to model better e.g. the solar system abundances. Also, the improved masses have an effect on the beta decay Q values which are important for the heating rate of the r process. The mass measurements are also essential to benchmark theoretical models predicting the masses for the experimentally inaccessible nuclei.

JYFLTRAP, a double Penning trap mass spectrometer [1], at the IGISOL (Ion Guide Isotope Separator On-Line) facility [2] at the University of Jyväskylä, has been successfully used to achieve high-precision mass measurements of several neutron-rich isotopes. Utilising the phase-imaging ion cyclotron resonance (PI-ICR) technique (e.g. [3]), also several low-lying isomeric states have been resolved. While currently they are not widely used in the astrophysical simulations, isomeric states can have a substantial effect on the r-process outcome [3,4]. In this contribution, I will present a few example cases of the ground and isomeric states of neutron-rich nuclei measured at JYFLTRAP with their effect on the reaction rates and the r-process simulations.

[1] Eronen, T., et al. JYFLTRAP: A Penning Trap for Precision Mass Spectroscopy and Isobaric Purification. Eur. Phys. J. A 48, 46 (2012).
[2] Moore, I.D., et al., Towards commissioning the new IGISOL-4 facility. Nucl. Inst. Meth. Phys. Res. B 317 (2013) 208.
[3] Nesterenko, D. A., et al. High-precision Measurements of Low-lying Isomeric States in In120–124 With the JYFLTRAP Double Penning Trap. Phys. Rev. C, vol. 108, no. 5, Nov. 2023.
[4] Misch, G. W., et al. Astromers: Nuclear Isomers in Astrophysics. Astrophys. J. Suppl. Ser., vol. 252, no. 1, Dec. 2020, p. 2.
[5] Misch, G. W., et al. Astromers in the Radioactive Decay of R-process Nuclei. The Astrophys. J. Lett., vol. 913, no. 1, May 2021, p. L2.

Speaker: Miikka Winter (University of Jyväskylä)

10:50 AM → 11:15 AM Coffee Break

11:15 AM → 12:00 PM Scientific Session: Session 10

11:15 AM Gamma-ray line observations for nuclear astrophysics

Nuclear astrophysics requires nuclear astronomy as it aims to understand compositional enrichment of matter in galaxies during cosmic evolution. Measuring characteristic gamma rays from nuclear transitions is among the most direct such astronomies. Yet, instrumental challenges from penetrating gamma rays and large instrumental backgrounds of such gamma-ray telescopes have constrained advances in this field, as instruments must be operated in space.
Cosmic radioactivities are by-products of nuclear fusion reactions within stars and stellar explosions, ejected into surrounding interstellar space. The decays produce characteristic gamma-rays, which have been measured by a first generation of such gamma-ray spectrometers. Among those radio-isotopes, 26Al, 60Fe, and 56Ni and 44Ti are most prominent, and have been measured in detail from different regions and sources. Short-lived 56Ni and 44Ti observations provide a diagnostic of the interiors of supernova explosions of the different types, whereas the longlived 26Al and 60Fe provide a characteristic trace of ejecta flows after immediate ejections.
We will summarize what has been learned from observations to date, and which challenges await the next generation of these instruments and missions. We then discuss the prospects of next-level science results in view of various projects in different countries.

Speaker: Roland Diehl (Max Planck Institut für extraterrestrische Physik, D-­‐85741 Garching, Germany)

11:40 AM First measurement of the $^{102}$Pd$(p,\gamma)^{103}$Ag reaction cross section in the Gamow window below $E_p = 2.5$\,MeV for the $p$-process nucleosynthesis

Sensitivity studies identify the $^{102}$Pd$(p,\gamma)^{103}$Ag reaction rate at temperatures $T_9 \simeq 2.0-3.0$ as an important nuclear input for both $p$- and $rp$-process nucleosynthesis. However, experimental information in the relevant Gamow window remains incomplete: no data are available below $E_{\mathrm{c.m.}} = 2.5$~MeV, and measurements at higher energies show sizable discrepancies, differing by factors of $\sim 1.5-3.0$. In this work, the $^{102}$Pd$(p,\gamma)^{103}$Ag cross section was measured for the first time at center-of-mass energies $E_{\mathrm{c.m.}} = 1.88$--2.58~MeV using a high-efficiency anti-Compton--anti-muon $\gamma$-ray spectrometer to suppress environmental and cosmic-ray backgrounds. Cross sections were extracted from characteristic $\gamma$ rays emitted in the decay of $^{103}$Ag, resolving the discrepancies among existing datasets and extending the measurements down to the lowest energies of astrophysical interest. The new low-energy data lead to a revised stellar reaction rate that is up to a factor of two higher than the currently adopted REACLIB and NON-SMOKER values in the astrophysically relevant $p$-process temperature range. These findings demonstrate the importance of improved low-energy experimental input for reducing nuclear physics uncertainties in $p$-process nucleosynthesis calculations.

Speaker: Dr Fulong Liu (CNS,University of Tokyo)

12:00 PM → 5:30 PM Excursion

5:30 PM → 9:00 PM Banquet

Fri, October 23

9:00 AM → 9:30 AM Morning Coffee

9:30 AM → 11:00 AM Scientific Session: Session 11

9:30 AM Helium enrichment and r-process heating in kilonovae

Kilonovae offer the potential to constrain the properties of high-density matter but the detailed sensitivities are still relatively poorly understood. An important question is whether the lifetime of the hypermassive neutron star remnant can be constrained from the kilonova signal. I will report a recent study suggesting that the lifetime can be constrained using the imprint of helium on the kilonova spectrum. The second part of the talk reports a recently developed scheme, called RHINE, to capture r-process heating in hydrodynamic simulations based on artificial neural networks.

Speaker: Oliver Just (GSI Darmstadt)

9:55 AM r-process with a first-principles neutron star merger model

We present our latest study of r-process based on a first-principle model of neutron star mergers, in which general relativity, neutrino transport, and magnetic field are self-consistently implemented. We find that magnetic field plays a pivotal role in the mass ejection and the determination of neutron richness. In this presentation, we discuss how neutron star mergers produce the solar-like r-process pattern as well as the actinide boost, which is observed in metal-poor stars. We also compare our result to that for black hole-neutron star mergers with the same model setup.

Speaker: Shinya Wanajo (YITP)

10:20 AM Nuclear equation of state at finite temperature compatible with low-energy experiments on Earth

The semi-realistic nucleonic interaction, particularly M3Y-P6 [1], has been shown to describe single-particle potentials from negative energy [2] to relatively high energy (+80MeV) [3] well, within the self-consistent mean-field (or Kohn-Sham) framework. Based on this success, the nuclear equation of state at finite temperature with M3Y-P6 is provided, which is compatible with the low-energy experiments and may be useful, e.g., for studying the supernovae. Its advantage for the spin properties [4,5] will also be mentioned.

[1] H. Nakada, Phys. Rev. C 87, 014336 (2013); Int. J. Mod. Phys. E 29, 1930008 (2020).
[2] H. Nakada and K. Sugiura, Prog. Theor. Exp. Phys. 2014, 033D02.
[3] H. Nakada and K. Ishida, Phys. Rev. C 109, 044614 (2024).
[4] K. Ishida and H. Nakada, Phys. Rev. C 111, 044610 (2025).
[5] H. Nakada and H. Iwata, Phys. Rev. C 113, 014315 (2026).

Speaker: Hitoshi Nakada (Chiba University)

10:40 AM Structure of nuclear matter below saturation density

Sub-saturation clustered nuclear matter constitutes a substantial part of neutron stars (NSs) and thus plays an essential role in multiple related phenomena, including NS cooling, oscillations and emission of gravitational waves. These complex layers are exposed to distinct astrophysical conditions, ranging from a cold-catalyzed state to a heated, out-of-equilibrium and partially dissolved matter in binary NS mergers and supernovae.
This contribution presents a unified treatment of the inhomogeneous NS region based on a nuclear energy density functional framework employing functionals accurately calibrated against both experimental and theoretical nuclear data [1]. The matter composition is determined by consistently varying the symmetry energy [2] while accounting for the finite-temperature effects [3]. Special emphasis is placed on the formation of exotic pasta shapes. I will demonstrate how microscopic (shell plus pairing) corrections, included on top of a semiclassical approach, affect the stability and occurrence of pasta phases [4]. Finally, I will introduce three-dimensional, fully quantum simulations at unprecedented scales, revealing the pasta sequence in NSs.

[1] G. Grams, N.N. Shchechilin, A. Sánchez-Fernández, W. Ryssens, N. Chamel and S. Goriely, Eur. Phys. Journ. A, 61, 35 (2025)
[2] N.N. Shchechilin, N. Chamel, A.I. Chugunov, Eur. Phys. Jour. A, 61, 132 (2025)
[3] G. Grams, N.N. Shchechilin, T. Diverres, A.F. Fantina, N. Chamel and F. Gulminelli, Universe, 11, 172 (2025)
[4] N.N. Shchechilin, N. Chamel, J.M. Pearson, A.I. Chugunov, A. Y. Potekhin, Phys. Rev. C, 109, 055802 (2024)

Speaker: Dr Nikolai Shchechilin (Institute of Science Tokyo)

11:00 AM → 11:25 AM Coffee Break

11:25 AM → 12:25 PM Scientific Session: Session 12

11:25 AM r-process-enhanced metal-poor stars studied with LAMOST and Subaru: elemental abundances and kinematics

High-dispersion spectroscopic observations have been conducted using the Subaru Telescope for metal-poor star candidates detected by China's spectroscopic survey telescope LAMOST, determining the chemical composition of about 400 objects [1, 2]. We have determined detailed abundances of heavy elements for objects that show excesses of elements heavier than iron, with analyzing the kinematics (orbital motions of these stars) in the Milky Way Galaxy. We report on the results of our series of studies on the r-process. (1) 65 objects showing excess of the r-process ([Eu/Fe]$>0.3$) are identified, among which 20 objects showing particularly large excess ([Eu/Fe]$>0.7$) are estimated based on the kinematics to have been formed in low-mass dwarf galaxies that accreted into the Galactic halos [3]. (2) Within the main substructure of the Galactic halo, the Gaia-Sausage-Enceladus (GSE), there is a group of r-process element-enhanced objects exhibiting similar orbital motion [4]. (3) One of these objects is an actinide-boost star showing an excess of the actinoid element Th, marking the example identified in GSE [5]. (4)A very metal-poor ([Fe/H] = -2.9) star that shows a large r-process excess also exhibits a large excess of Zn, suggesting that its origin is related to a supernova with high explosive energy [3].
[1] Aoki et al. 2022, ApJ, 931, 146
[2] Li et al. 2022, ApJ, 931, 147
[3] Lin et al. et al. 2026, ApJ 1003, 75
[4] Zhang et al. 2024, ApJ 966, 174
[5] Lin et al. 2025, ApJ 984, L43

Speaker: Wako Aoki (National Astronomical Observatory of Japan)

11:45 AM Phosphorus enrichment on the young side of the Milky Way: age-resolved constraints on Galactic chemical evolution

Phosphorus is an odd-Z element of astrobiological and nucleosynthetic interest, yet its Galactic origin remains poorly constrained because observable stellar P lines are weak and mostly located outside the optical wavelength range. I will present phosphorus abundance measurements for 102 evolved stars, including 82 giants in 24 open clusters and 20 classical Cepheids, based on high-resolution near-infrared spectra obtained with GIANO-B.

By combining P abundances with independently constrained stellar and cluster ages, this sample provides an age-resolved view of phosphorus enrichment on the young side of the Milky Way disk. We confirm the previously observed modest decline of [P/Fe] with increasing [Fe/H] around solar metallicity. More importantly, the open-cluster sample reveals a structured P–age relation, with two apparent regimes. For clusters older than about 1 Gyr, phosphorus abundance increases with stellar age, suggesting that these systems preserve a fossil record of diverse enrichment histories and more intense star formation in earlier Galactic environments. In contrast, clusters younger than about 1 Gyr and Cepheids show a nearly flat trend with age, consistent with a more quiescent recent chemical history in the local disk.

This age-resolved abundance pattern provides an empirical benchmark for Galactic chemical-evolution models of phosphorus. While massive stars remain the dominant expected source of P, the behaviour of the youngest populations may point to an additional delayed or metallicity-dependent contribution, potentially from lower- or intermediate-mass stellar sources. I will also discuss how robust spectral-synthesis and line-selection methods, including recent developments in PySME for survey-scale abundance analysis, can help extend such nucleosynthetic constraints to larger stellar samples.

Speaker: Mingjie Jian (Institute of Astronomy, University of Cambridge)

12:05 PM Multidimensional Dynamics and Multimessenger Signatures of Magnetorotational Supernovae

Magnetorotational (MR) core-collapse supernovae are driven by rapid rotation and strong magnetic fields and may lead to energetic explosions. Understanding the multidimensional fluid dynamics of these events is essential for predicting their observational signatures and nucleosynthetic implications. To this end, we perform three-dimensional general relativistic magnetohydrodynamic (GRMHD) simulations of rotating, magnetized progenitors with spectral neutrino transport.

In models with sufficiently rapid rotation and strong magnetic fields, our simulations produce MHD jets and characteristic gravitational-wave (GW) signals. In particular, we find low-frequency GW emission associated with neutrino memory, together with strong circular polarization arising from non-axisymmetric instabilities in the vicinity of the proto-neutron star.

The same multidimensional dynamics that drive MR explosions, including rapid shock expansion and the formation of collimated outflows, can also shape the thermodynamic histories of the ejecta that are relevant to heavy-element production. Tracer-particle trajectories extracted from our 3D GRMHD simulations allow us to characterize these nucleosynthesis-relevant conditions.

In this presentation, we will focus primarily on the explosion dynamics and GW characteristics of our MR supernova models. We will also briefly discuss the implications of the simulated ejecta dynamics for the conditions of element production.

Speaker: Shota Shibagaki (Wrocław University of Science and Technology)

12:25 PM → 1:40 PM Lunch and Coffee

1:40 PM → 3:10 PM Scientific Session: Session 13

1:40 PM Beta decay and electron capture calculations related to astrophysical applications

Beta decay and electron capture (EC) are processes mediated by the weak nuclear interaction. Both play a prominent role in the late stages of stellar evolution and during core-collapse supernova explosions. In this talk, I will give an overview of our recent work on calculating EC and beta-decay rates in stellar environments and their implications for core-collapse supernova dynamics [1,2]. Rates for a large number of nuclei from $Z=20$ to $Z=50$ are calculated within the nuclear density functional theory (DFT) framework, including finite-temperature effects under high-density stellar conditions. It is demonstrated how increasing density and temperature can significantly impact the weak-interaction rates.

Beta-decay rates are also important for determining the timescale of the nuclear $r$-process. Using a quantified DFT framework, we have computed beta-decay rates for $r$-process nuclei, including contributions from both allowed and first-forbidden transitions [3]. The new rates are found to slow down the synthesis of heavy elements in the $r$-process. Lastly, I will discuss how weak-decay rate calculations can be accelerated and their model uncertainties estimated using recent developments in data-driven emulators [4].

[1] A. Ravlic, S. Giraud, N. Paar, R. Zegers Phys. Rev. C 112, L032801 (2025).

[2] T. Dasher, A. Ravlic, S. Lalit, E. O'Connor, K. Godbey, Phys. Rev. D 113, 123041 (2026).

[3] A. Ravlic, Y. Saito, W. Nazarewicz, Phys. Rev. C 113, 045802 (2026).

[4] L. Jin, A. Ravli\'c, P Giuliani, K. Godbey, W. Nazarewicz, Phys. Rev. Research 7, 043347 (2025).

Speaker: Ante Ravlic (Facility for Rare Isotope Beams, Michigan State University)

2:05 PM Experimental studies of β-decay properties of very neutron-rich nuclei relevant to the r process

The search for the limits of nuclear existence at extreme isospin toward the neutron drip line is at the forefront of modern nuclear physics. Along this line, the astrophysical rapid neutron capture process (r-process), which is responsible for the synthesis of about half of the elements heavier than iron [1], provides one of the strongest motivations. The β-decay properties of very neutron-rich nuclei are key inputs to r-process calculations, and where direct data are missing, they serve as essential constraints on the theoretical models employed [2]. In particular, half-lives (T₁/₂) set the timescale of the reaction flow toward heavier masses, while β-delayed neutron emission probabilities (Pₓₙ) control the availability of late-time neutrons and shape the final abundance pattern.
In this talk, we will present a variety of experiments focusing on the β-decay properties of very neutron-rich nuclei, namely half-lives, β-delayed neutrons, and delayed γ rays, covering wide regions of the nuclear chart [3–5]. These measurements were performed at the RIBF facility using intense radioactive-isotope beams produced by in-flight fission and separated by BigRIPS, combined with complementary experimental apparatus: the high-efficiency neutron counter BRIKEN [6], high-efficiency γ-ray detector arrays, and the decay station coupled with multi-reflection time-of-flight (MRTOF) mass spectrographs [7]. Recent results, including new decay rates in the A ≈ 110 region [8] and β-decay half-lives beyond the N = 126 shell closure [9], will be discussed together with their impact on r-process calculations and prospects for reaching further toward the drip line.
[1] J. J. Cowan et al., Rev. Mod. Phys. 93, 015002 (2021).
[2] M. R. Mumpower et al., Prog. Part. Nucl. Phys. 86, 86 (2016).
[3] S. Nishimura et al., Phys. Rev. Lett. 106, 052502 (2011).
[4] G. Lorusso et al., Phys. Rev. Lett. 114, 192501 (2015).
[5] V. H. Phong et al., Phys. Rev. Lett. 129, 172701 (2022).
[6] A. Tolosa-Delgado et al., Nucl. Instrum. Methods Phys. Res. A 925, 133 (2019).
[7] M. Rosenbusch et al., Nucl. Instrum. Methods Phys. Res. A 1047, 167824 (2023).
[8] V. H. Phong, S. Nishimura et al., submitted.
[9] V. H. Phong, S. Nishimura et al., in preparation.

Speaker: Vi Phong (Radioactive Isotope Physics Laboratory, RIKEN Nishina Center)

2:30 PM Collisional-Radiative Lanthanide & Actinide Data for non-LTE Kilonova Spectral Modelling

Recent infrared observations obtained with the James Webb Space Telescope (JWST) have significantly advanced the study of kilonovae, delivering the first detailed nebular-phase spectra of AT 2023vfi, only the second kilonova to be observed spectroscopically. The spectra exhibit prominent mid-infrared emission features, some of which have been tentatively linked to r-process elements such as tellurium. With substantially broader wavelength coverage and improved sensitivity compared to the earlier observations of AT 2017gfo, these data place stringent demands on atomic physics input, particularly comprehensive collisional–radiative datasets required to interpret kilonova spectra in the nebular-phase regime.

I present large-scale, calibrated collisional-radiative atomic structure calculations for lanthanide and actinide ions, coupled with nucleosynthesis yields derived from hydrodynamical simulations of binary neutron star mergers, to model late-time kilonova spectra in the non-local thermodynamic equilibrium regime. I explore the role of heavy-ion nebular emission in shaping the mid-infrared features observed in AT 2023vfi, which have not yet been securely attributed to specific elements. I also compare detailed modelling with the currently proposed alternative explanation for these features, namely thermal dust emission. In addition, I will quantify the impact of using detailed collisional-radiative datasets versus widely adopted approximations, both on inferred elemental abundances and on the ability of emission models to reproduce the observed spectra.

Speaker: Andreas Flörs (GSI Helmholtz Centre For Heavy Ion Research)

2:50 PM The r-Process: A Complete Survey and the Impact of Ab Initio Masses

The rapid neutron-capture (r-) process is responsible for producing approximately half of the elements heavier than iron in the Universe. However, the astrophysical sites capable of generating the required extreme neutron fluxes remain uncertain. Detailed hydrodynamical simulations of proposed scenarios - such as binary neutron star mergers, magneto-rotational supernovae, and collapsars - are computationally demanding and subject to significant uncertainties, including the nuclear equation of state, neutrino interactions, and progenitor properties.

To address these challenges, we adopt a site-independent approach, based on a parametric density profile. Using nuclear network calculations, we explore a broad range of initial electron fractions, entropies, and expansion timescales. Our results reproduce those obtained in hydrodynamical simulations and extend beyond currently explored conditions. We use Bayesian inference to explore the conditions that are required to produce observed stellar r-process abundance patterns, finding that two distinct ejecta components are required.

In addition to astrophysical uncertainties, poorly constrained nuclear properties introduce significant theoretical uncertainties. Most nuclei along the r-process path are experimentally inaccessible, making reliable theoretical predictions of nuclear masses, reaction rates, and fission properties essential. We investigate the impact of ab initio nuclear mass predictions around the N=82 shell closure (associated with the second r-process peak), calculated using the Valence-Space In-Medium Similarity Renormalization Group (VS-IMSRG) method.

Speaker: Jan Kuske (TU Darmstadt)

3:10 PM → 3:35 PM Coffee Break

3:35 PM → 4:40 PM Scientific Session: Session 14

3:35 PM Recent Observations of Pulsar Wind Nebulae and Supernova Remnants

Supernova remnants and pulsar wind nebulae are nearby laboratories for studying some of the most extreme conditions in the Universe. As the debris of massive star explosions and the environments of newly born compact objects, they provide unique and nearby probes of supernova progenitors, explosive nucleosynthesis, neutron star birth properties, relativistic winds, magnetic fields, and particle acceleration up to ultra-high energies. They also reveal a remarkable diversity or “zoo” of phenomena associated with the deaths of massive stars. In this talk, I will highlight recent multi-wavelength observations of pulsar wind nebulae and supernova remnants that are shedding new light on this field. I will also discuss how upcoming facilities, together with new and forthcoming JWST studies, will open a new window on compact remnants, supernova engines, and the origin of the heavy elements.

Speaker: Prof. Samar Safi-Harb (University of Manitoba)

4:00 PM The experimental study on the compound neutron-capture rate of 130Sn via (d,p) surrogate reaction

Abstract: The neutron-capture rate in the rapid neutron-capture process (r-process) is one of the major sources of uncertainty, leaving the physical conditions for the r-process not fully constrained [1]. It was suggested that the compound-nucleus neutron-capture rate of 130Sn has a large impact on final r-process elemental abundances [1, 2]. We performed a (d,p) surrogate-reaction measurement for 130Sn in inverse kinematics at the RIKEN RIBF, OEDO SHARAQ beamline. The heavy-ion residues from the reaction (A = 129-131) were identified with the SHARAQ spectrometer, and the γ‑emission probabilities along the excitation energy of the compound nucleus, 131Sn, near the one‑neutron separation energy were obtained from the number ratios between the different-mass heavy-ion residues as a function of excitation energy. The neutron-capture cross-section of 130Sn was constrained based on the γ-emission probabilities. The experimental details and preliminary results for the neutron-capture cross section of 130Sn will be presented.

References: [1] M.R. Mumpower et al. Prog. Part. Nucl. Phys. 86, 86-126 (2016)
[2] S. Michimasa et al. Nucl. Instrum. Methods Phys. Res. B 540, 194-198 (2023)

Speaker: Dr Sunghan Bae (IRIS, IBS)

4:20 PM Poster Award and Closing

Speaker: Shunji NISHIMURA (RIKEN)