ARIS2026 (-1)

9 Feb 2026, 09:00 → 10 Feb 2026, 18:20 Asia/Tokyo

main conference hall, meeting rooms (Palthe Iizaka)

Prior to the main ARIS2026 conference, we are pleased to announce the Pre-Conference named ARIS2026(-1), to be held at the same venue.

• Dates: February 9 (Mon) – 10 (Tue), 2026
  
  

• Venue: Palthe Iizaka, Iizaka Onsen, Fukushima, Japan
  
  

This pre-conference will focus on experimental and theoretical studies in radioactive isotope science,  providing a forum for researchers—especially from Asian countries—to present their work, exchange ideas,  and promote collaborations in preparation for ARIS2026.

Details on the program  will be announced later.
We look forward to your participation.

Please give us ANY comments from here. 

Note this is not the indico for the fifth ARIS conference (ARIS2026). For contributing to the main ARIS conference, please visit official site.

 

 

From Fukushima Station (Tohoku Shinkansen) to Iizaka Onsen_v2.pdf

Monday 9 February

registration

12:15 lunch

2nd Session

1 What does the Q moments in Cd isotopes indicate?

Speaker: Yutaka Utsuno (Japan Atomic Energy Agency)

2 TBA

Speaker: Marco Tik Tsun Yeung

3 TBA

Speaker: Dr Daisuke Suzuki (Department of Physics, University of Tokyo)

4 Low-energy nuclear reactions at OEDO and HIMAC

Speaker: Nobuaki IMAI (CNS, Univ. of Tokyo)

5 Pair transfer reaction measurement at RCNP

Speaker: Dr Shinsuke Ota (RCNP, Osaka University)

2nd session

6 Arch behaviour of charge radii with Fayans pairing

Arch behaviour of charge radii of Ca isotopes has been a long standing problem in nuclear theory. Recently, it was proposed that the Fayans pairing is a possible solution to obtain it using nuclear density functional theory. In this talk, we will explain the mechanism why the Fayans pairing can show the arch behaviour.

Speaker: Dr Tomoya Naito (The University of Tokyo)

7 Ni-86: Possible doubly-magic nucleus with neutron halo

The self-consistent mean-field calculation with semi-realistic interactions has predicted that N=58 becomes a magic number at Ni, at which n2s1/2 is the highest occupied orbit. Thereby, Ni-86 can be very distinguished, as it is a doubly-magic nucleus and possesses a neutron halo simultaneously. With the least ambiguities in the many-body wave function, it may provide a unique opportunity to investigate, e.g., reaction mechanisms in halo nuclei.

Speaker: Hitoshi Nakada (Chiba University)

8 Measurement of B(M1) values for l-forbidden transitions and evaluation of mesonic effects in neutron-rich chlorine isotopes

We aim to investigate mesonic effects in nuclei by measuring B(M1) values for l-forbidden (Δl = 2, ΔJπ = 1⁺) transitions. The transition strengths were obtained from level lifetimes measured using the line-shape analysis method with Ge detectors. In this study, we performed two in-beam γ-ray spectroscopy experiments to determine the lifetimes of the first excited states in 39Cl (CAGRA campaign, RCNP) and 43Cl (HiCARI campaign, RIBF). The analysis results will be presented.

Speaker: yasutaka yamamoto

9 Study on the compound nucleus neutron-capture reaction of $^{130}$Sn using (d,p) surrogate reaction for understanding the r-process

The rapid neutron capture process, r-process, is responsible for the production of more than half of the elements heavier than iron. However, the physical conditions and astronomical sites of the r-process have not yet been determined. The lack of experimental data on the properties of the involved exotic nuclei is a significant source of uncertainty. In particular, the difficulty of directly measuring neutron capture reactions for short-lived nuclei hinders the determination of neutron capture rates in the r-process. The area near $^{132}$Sn (Z = 50, N = 82) is a critical region in the r-process. A drastic decrease in the neutron capture rate when crossing the neutron magic number 82 is expected for the compound neutron capture due to the large energy gap after the shell closure. Due to a lack of experimental data, there are large uncertainties in neutron capture rates for this region, which result in large ambiguities in r-process conditions and the calculation of final elemental abundances.
The neutron capture rates can usually be determined with the knowledge of $\gamma$-emission probabilities of the neutron unbound states. However, the low $\gamma$-emission probabilities and usually low $\gamma$-ray detection efficiencies have been experimental obstacles. At the OEDO-SHARAQ beamline in RIKEN RIBF, an alternative method to identify experimental $\gamma$-emission probability was developed, in which the heavy reaction residues are identified with the SHARAQ spectrometer, and the $\gamma$-emission probability can be obtained based on the number of heavy residues with increased neutron numbers. The $^{130}$Sn(d,p) reaction measurement in inverse kinematics was performed using a $^{130}$Sn secondary beam to identify the $\gamma$-emission probabilities in $^{131}$Sn with this method, alongside $^{130}$Te and $^{124}$Sn beams for reference reactions. The kinetic energies of the secondary beams were degraded to about 20 MeV/u. We identified Sn isotopes with A = 129, 130, and 131, which correspond to two, one, and zero neutron emissions after the reaction, respectively, and the $\gamma$-emission probability near the one-neutron separation energy of $^{131}$Sn was explored. Experimental details and preliminary results, including those for the reference isotopes, will be presented.

Speaker: Dr Sunghan Bae (IRIS, IBS)

10 TBA

Speaker: Park Chaeyeon (IRIS/IBS)

15:45 coffee break

Poster Session

11 KISS-1.5 to reveal the origin of heavy-element synthesis

Speaker: Yoshikazu HIRAYAMA (IPNS, KEK)

12 Development of wire carpets for the new-generation helium gas catcher at the SLOWRI facility in RIKEN RIBF

Speaker: Aiko Takamine (Kyushu University)

13 TBA

Speaker: Kentaro Yako (CNS, University of Tokyo)

14 Design of Low-Pressure Vertical Drift Chamber Using Garfield++ for High-Rate Environments

To experimentally quantify isoscalar proton–neutron pairing correlations in atomic nuclei, we plan systematic measurements of nucleon-pair transfer reactions. In order to separate the isoscalar (T = 0) and isovector (T = 1) pair-transfer strengths, it is effective to combine the (α,⁶Li) reaction, in which both components can be excited, with the (d,α) reaction, in which preferentially selects the isoscalar component. A new physics quantity called pair polarizability has been suggested, which can be determined by measuring the pair-removal and pair-addition strengths up to the high-excitation-energy region. Theoretically, an enhancement of the proton-neutron pair polarizability around $^{116}$Sn along the tin isotope chain is predicted.

For this purpose, we are upgrading an experimental system based on the Large Acceptance Spectrometer (LAS). The typical energy of the reaction products, $^6\rm{Li}$ and $^4\rm{He}$, is 10 - 15 MeV/u and the typical total rate at the focal plane is expected to be 6 Mcps with a signal-to-noise ratio of 0.1% due to inelastic scattering. In such a high-rate environment, pile-up becomes a primary limiting factor, and detector compactness, which helps suppress event overlap, is therefore an important design guideline. In addition, from the viewpoint of long-term and sustainable operation, the replacement of cathode foils with cathode-wire configurations, which offer better material availability, as well as the reduction of readout channels to suppress overall costs, are important issues. Furthermore, comprehensive optimization is required, taking into account practical aspects such as fabrication, installation, operation, and maintenance.

The design of a low-pressure vertical drift chamber (LP-VDC) for the LAS upgrade is ongoing .Assuming an operation with 10-kPa iso-butane gas, for the various geometrical configurations, including the wire arrangement, plane spacing, and cathode structure (foil or wire), the detection efficiency and the position resolution are estimated by using a simulation toolkit Garfield++.

In this presentation, the procedure of the simulation and the results for the several configurations will be discussed.

Speaker: Fumiya Furukawa (RCNP)

15 TBA

Speaker: Nishioka

16 Current Status of The Segmented 139La-GPS Scintillation Crystal Detector as a New β-implant Detection Tool

The rapid neutron capture (r-) process gained significant amounts of interest as a means of nucleosynthesis of elements in astrophysical environments. Consequently, there have been ongoing efforts to better understand it from the perspective of both, nuclear physics and astrophysics. From the standpoint of nuclear physics, such efforts include measurements of β-decay and delayed neutron emissions of the r-process elements for a more accurate input for the calculations in relation to its theoretical modelling [1].

Typically, β-γ spectroscopies are conducted with implantation detectors at fragmentation facilities such as the Silicon strip detectors at Radioactive Isotope Beam Factory (RIBF). However, these detectors lack fast timing response for the purpose of neutron time-of-flight measurements of the delayed neutron emissions. To address this limitation, a detector was developed with segmented Yttrium orthosilicate (YSO) scintillation crystal (Z ≈ 35, ρ ≈ 4.5 g/cm^3). The characteristics of the YSO detector enable an 80% correlation efficiency with a 3mm correlation radius between implant events and β-decay events [2].

The success of this detector encouraged the development of Lanthanum-enriched, segmented (Gd, La)2Si2O7:Ce (La-GPS) scintillation crystal (Z ≈ 51, ρ ≈ 5.2 g/cm^3) detector with the aim of achieving better correlation radius and higher energy resolution compared to the YSO, and faster timing response than Silicon strip detectors [3]. This presentation showcases the current status of the La-GPS scintillation crystal detector of (1.5 x 1.5)mm arranged into a 32 x 32 array in the x-y plane.

References
[1] M. R. Mumpower et al., “The impact of individual nuclear properties on r-process nucleosynthesis,” Prog. in Particle and Nucl. Phys., vol. 86, pp. 86-126, 2016.
[2] R. Yokoyama et al., “Segmented YSO Scintillation Detectors as a New β-Implant Detection Tool for Decay Spectroscopy in Fragmentation Facilities,” Nucl. Instrum. Methods Phys. Res. A, Accel. Spectrom. Detect. Assoc. Equip., vol. 937, pp. 93–97, 2019.
[3] A. Suzuki et al., “Fast and high-energy-resolution oxide scintillator: Ce-Doped (La,Gd)2Si2O7,” Appl. Phys. Express, vol. 5, no. 10, p. 102601, 2012.

Speaker: Yasmin Anuar

Tuesday 10 February

4th session

17 Development of a VOICE for α Induced reaction cross section measurement

Ionization chambers are widely used in nuclear physics experiments and their role has recently expanded to active target applications. VOICE (Vertically Oriented wire Ionization Chamber with sEgmentation) is being developed at the Center for Exotic Nuclear Studies (CENS), Institute for Basic Science (IBS), to enable direct measurements of alpha induced reaction cross sections. The detector adopted vertically oriented electrodes and a Frisch grid to enhance energy resolution and employs a $^{4}$He active gas target to directly observe reaction products in inverse kinematics. For commissioning, VOICE will measure the $^{40}$Ar + $\alpha$ reaction using a well established channel to validate its performance. The thick target method will be adopted to scan a broad center of mass energy region and demonstrate the detector’s capability. The commissioning experiment is currently being prepared at RAON. In this presentation, more details of the detector status and commissioning plan will be discussed.

Speaker: Dr Minju Kim (Institute for Rare Isotope Science)

18 $\beta$-$\gamma$ spectroscopy of $^{156}$Pr nuclei

The neutron-rich rare-earth nuclei in the A$\sim$160 mass region lie in one of the deformed sectors of the nuclear chart. Examining these nuclei helps us understand the evolution of nuclear deformation. The systematics of the first excited $2^+$ states in even-even nuclei suggest that Nd ($Z=60$) isotopes exhibit among the largest ground-state deformations in the A$\sim$160 region. Experimental data near such nuclei in the far-from-stability regime have been limited, but advances in radioactive-beam facilities have made their study accessible. $\beta$-$\gamma$ spectroscopy serves as an important probe to study the nuclear structure. These studies are of astrophysical importance for understanding the origin of the rare-earth peak in the abundance distribution of the rapid neutron-capture process of nucleosynthesis, a feature thought to arise from the combined effects of maximum in nuclear deformation and $\beta$-decay. In this work, we investigate the $\beta$-$\gamma$ spectroscopy of $^{156}$Pr ($Z=59$, $N=97$) to populate its daughter $^{156}$Nd ($Z=60$, $N=96$).
The experiment was conducted at RIBF, RIKEN, using in-flight fission of a 345 MeV/nucleon $^{238}$U beam on a Be target to produce neutron-rich rare-earth isotopes. The isotopes were separated and identified using the BigRIPS separator. An active stopper, WAS3ABi, was used for ion- and $\beta$-detection, while an array of Ge detectors, EURICA, was used for $\gamma$-ray detection. This enabled us to perform the $\beta$-$\gamma$ spectroscopy.
In the presentation, first $\beta$-$\gamma$ decay spectroscopy results for $^{156}$Pr will be presented, providing nuclear structure information relevant to rare-earth peak formation.

Speaker: Mukul Khandelwal (RCNP, The University of Osaka)

19 Universal aspects of weakly bound 3-body cluster gas states and its origin

In our previous study, we found that the ${}^8\mathrm{He}(0_2^+)$ state is dominantly described by a weakly bound $\alpha + {}^2n + {}^2n$ cluster structure, and we pointed out its similarity to the $3\alpha$ gas-like state in ${}^{12}\mathrm{C}$. Based on this observation, it is considered weakly bound 3-body $S$-wave cluster states (here denoted as "3-cluster gas states") tend to appear near their corresponding energy thresholds. However, our calculations also indicate that the ${}^8\mathrm{He}(0_2^+)$ state involves a mixing between a spatially correlated $\alpha + {}^2n$ configuration and a distant ${}^2n$ cluster.
To clarify the origin of the 3-cluster gas state, we systematically vary the inter-cluster interactions between $\alpha$-${}^2n$ and ${}^2n$-${}^2n$ and demonstrate the emergence of a pure $\alpha+{}^2n+{}^2n$ 3-cluster gas state in the $0_2^+$ state. Through this analysis, we find that 3‑cluster gas states appear when the inter‑cluster interactions are taken to be identical, indicating that the 3‑cluster gas is a universal feature that can arise not only in systems of identical bosons but also in non‑identical cluster systems.

Speaker: 中川 昂星 (京都大学)

20 The research on nuclear fission with the relativistic mean field theory

Nuclear fission is a phenomenon in which a nucleus splits into two (or more) lighter nuclei. From a theoretical perspective, fission has been studied using macroscopic approaches such as the Langevin method, as well as the microscopic frameworks including the DFT(density functional theory) and GCM(generator coordinate method). A microscopic understanding of nuclear fission at the nucleonic level is essential. Since fission predominantly occurs in the actinide and superheavy region, relativistic effects play an important role, particularly because the spin-orbit interaction is naturally incorporated in relativistic formulations. In this study, nuclei are described within the relativistic mean field (RMF) theory[1], in which the nuclear force is effectively modeled through the exchange of mesons such as $\sigma,\omega,\rho, \text{and} \pi$, between nucleons.
When a nucleus undergoes fission into two fragments, their mass ratio is generally asymmetric due to the quantum shell effects. Therefore, at least two collective deformation parameters are required to describe the fission process: the nuclear elongation (quadrupole deformation, $\beta_{20}$) and the reflection asymmetry (octupole deformation, $\beta_{30}$).
In this research, we focus on spontaneous fission, which proceeds through quantum tunneling in the deformation space $(\beta_{20},\beta_{30})$. The WKB(Wentzel-Kramers-Brillouin) approximation is often used as the simplest method to evaluate this tunneling probability and to determine the fission path. Within this approximation, both the potential energy surface (PES) $V(q)$ and the mass parameters $B(q)$ are required. The PES V(q) represents the nuclear energy as a continuous function of deformation $q=(\beta_{20},\beta_{30})$ and reflects the static properties of fission, while the mass parameters $B(q)$ correspond to the inertia in the deformation space and describe the dynamical aspects of the fission process.
The PES is gained by the constrained RMF with respect to the deformation coordinates $q=(\beta_{20},\beta_{30})$. The mass parameters are evaluated using several approaches, including the cranking approximation[2], the adiabatic time-dependent Hartree-Fock-Bogoliubov (ATDHFB) method[3,4], and the quasiparticle random-phase approximation (QRPA)[5]. While there exist several calculations of mass parameters including octupole deformation within the cranking and ATDHFB approaches, QRPA-based calculations have so far been restricted to quadrupole deformation, with triaxiality taken into account. As a result, the evaluation of the spontaneous-fission lifetime $\tau_\text{SF}$ still suffers from significant uncertainties.
The aim of this research is to evaluate collective mass parameters within the QRPA framework in the two-dimensional deformation space $(\beta_{20},\beta_{30})$ and thereby improve the precision of fission lifetime.
In this talk, we will show the results for the 1-dimensional PES constrained on the quadrupole deformation only and present the current status.
[1] Y.K. Gambhir, P. Ring, and A. Thimet, Annals of Physics 198, 132-179 (1990).
[2] A. Baran, J.A. Sheikh, J. Dobaczewski, and W. Nazarewicz, PRC 84, 054321 (2011).
[3] J. Sadhukhan et al., PRC 88, 064314(2013).
[4] J. Zhao et al., Phys. Rev. C 93, 044315(2016)
[5] K. Washiyama, N. Hinohara, T. Nakatsukasa, PRC 103, 014306 (2021).

Speaker: Shion Yoshikawa (RCNP, the University of Osaka)

10:40 break

5th session

21 Role of deformation and pairing correlations in soft E1 excitations of the Borromean nucleus 19B

Speaker: Masayuki Yamagami (University of Aizu)

22 Multiconfiguration time-dependent Hartree-Fock method for many particle tunneling

We propose a multiconfiguration time-dependent Hartree–Fock (MCTDHF) method for ab initio descriptions of many-body tunneling in nuclear processes. Originally developed for intense laser-driven multielectron dynamics [1], the MCTDHF method employs a configuration interaction (CI) wavefunction in which both the CI coefficients and single-particle functions are treated as time-dependent variational parameters. This framework enables a compact and efficient representation of quantum tunneling dynamics at a reasonable computational cost. In this contribution, we review our previous work on electron dynamics [2], discuss possible different formulations of MCTDHF, and present some numerical results for the scattering of two alpha particles in one dimension [3,4].

[1] T. Kato and H. Kono, "Time-dependent multiconfiguration theory for electronic dynamics of molecules in an intense laser field", Chem. Phys Lett. 392, 533 (2004),
[2] T. Sato, H. Pathak, Y. Orimo, and K. L. Ishikawa, "Time-dependent multiconfiguration self-consistent-field and time-dependent optimized coupled-cluster methods for intense laser-driven multielectron dynamics", Can. J. Chem. 101, 698 (2023),
[3] P.-G. Reinhard, R.Y. Cusson, and K. Goeke, “Time evolution of coherent ground-state correlations and the TDHF approach”, Nucl. Phys. A 398, 141 (1983) .
[4] N. Hasegawa, K. Haginob, and Y. Tanimura, “Time-dependent generator coordinate method for many-particle tunneling”, Phys. Lett. B 808, 135693 (2020).

Speakers: Takeshi Sato, Takumi Ogata, Dr Tomoya Naito (The University of Tokyo), Yugo Komai

23 TBA

Speaker: Nori AOI (RCNP, Osaka Univ.)

12:20 lunch break

Round Table Discussion