6th International Workshop on Quasi-Free Scattering with Radioactive-Ion Beams: QFS-RB 2026

27 Sept 2026, 15:00 → 2 Oct 2026, 17:30 Asia/Tokyo

Takayama Municipal Cultural Hall, 1-188-1 Showacho, Takayama City, Gifu Japan

Yuki Kubota (RIKEN Nishina Center), Kazuki Yoshida (RCNP)

The 6th International Workshop on Quasi-Free Scattering with Radioactive-Ion Beams (QFS-RB 2026) will take place at Takayama Municipal Cultural Hall, Gifu Japan on Sep. 28th – Oct. 2nd. The workshop is jointly organized by RCNP Osaka, RIKEN Nishina Center, and the TOPTIER project of IBS and RIKEN.

The workshop will be the sixth in a series of international workshops dedicated to the topic of applying QFS in inverse kinematics with radioactive beams, which started 2008 in Trento (QFS-RB 2008), with following workshops in Azores (QFS-RB 2013), York (QFS-RB 2017), Maresias (QFS-RB 2019) and Lefkada (QFS-RB 2023).

Circulars:

The first circular: QFS-RB2026_First_circular.pdf
The second circular: QFS-RB2026_Second_circular.pdf
The final circular: QFS-RB2026_Final_circular.pdf

 

Key Topics:

• Quasi-free scattering with hadrons and electrons as probes
• Single-particle state and spectroscopic factors
• Short-range correlations
• Direct reaction theory
• Pair interactions
• Structure effects
• Polarisation observables
• Clustering in nuclei
• Spectroscopy beyond the driplines
• Status and future prospects of quasi-free scattering with radioactive ion beams

 

Workshop Venue:

The workshop is held at akayama Municipal Cultural Hall. Please see Venue for details.

Confirmed Speakers (alphabetical order)

• Seisho Abe (U. Tokyo)
• Mack Atkinson (Reed College)
  
• Carlos Bertulani (East Texas A&M)
• Stefano Brolli (U. Of Milan)
• Jie Chen (Southern University of Science and Technology)
• Quentin Delignac (IJCLab Orsay)
• Mario Gomez-Ramos (U. Seville)
• Nobuo Hinohara (Tsukuba Univ.)
• Naoyuki Itagaki (OMU)
• Masaaki Kimura (RIKEN)
• Dae Ik Kim (Pusan National University)
• Andrea Lagni (TU Darmstadt)
• CheongSoo Lee (IBS)
• Jin Lei (Tongji University)
• Pengjie Li (Fudan Univ.)
• Hao Liu (Tongji University)
• Xiaoyu Liu (The University of Hong Kong)
• Taichi Miyagawa (RCNP)
• Nikhil Mozumdar (TU Darmstadt)
• Dien Nguyen (The University of Tennessee, Knoxville)
• Tetsuo Noro (Kyushu Univ.)
• Taishi Ochi (Tsukuba Univ.)
• Shoya Ogawa (Kyushu Univ.)
• Valerii Panin (GSI, Darmstadt)
• Stefanos Paschalis (University of York)
• Yelei Sun (Beihang University)
• Satoru Terashima ( Institute of Modern Physics)
• Ryotaro Tsuji (U. Tokyo)
• Manuel Xarepe (TU Darmstadt)
• Zaihong Yang (Peking University)
• JiChao Zhang (RCNP)
  

International Advisory Committee:

• Thomas Auman (TU Darmstadt)
• Carlo Barbieri (University of Milan)
• Didier Beaumel (JCLab Orsay)
• Carlos Bertulani (Texas A&M)
• Willem H. Dickhoff (Washington University in St. Louis)
• Or Hen (MIT)
• Jenny Lee (The University of Hong Kong)
• Antonio M. Moro (Universidad de Sevilla)
• Takashi Nakamura (Science Tokyo)
• Kazuyuki Ogata (Kyushu University)
• Stefanos Paschalis (University of York)
• Marina Petri (University of York)
• Stefan Typel (GSI)
  
• Tomohiro Uesaka (RIKEN)

Local Organizing Committee:

• Yuki Kubota (Co-chair, RIKEN)
• Kazuki Yoshida(Co-chiar, RCNP/RIKEN iTHEMS)
• Yoshiki Chazono (Kyushu Univ.)
• Youngman Kim (IBS)
• Shumpei Koyama (Tohoku Univ.)
• Shoya Ogawa (Kyushu Univ.)
• Junki Tanka (RCNP)

Sponsors:

This workshop is sponsored by RCNP/Osaka, JST ERATO Sekiguchi Three-Nucleon Force Project, RIKEN iTHEMS, and the TOPTIER project of IBS and RIKEN.

 

QFS-RB2026_Final_circular.pdf

QFS-RB2026_First_circular.pdf

QFS-RB2026_Second_circular.pdf

TakayamaRestaurant.pdf

Sunday 27 September

15:00 → 18:00 Welcome reception: Welcome reception Hida Hotel Plaza

Monday 28 September

09:30 → 10:00 Registration

10:00 → 10:10 Welcome address

10:00 Welcome address

10:10 → 11:40 28th Morning session 1 (Chair: K. Ogata)

10:10 Proton-induced deuteron knockout on 12C and 16O at 226 MeV

Speaker: CheongSoo LEE (IBS, Korea)

10:40 Formation mechanism of three-nucleon clusters probed by cluster knockout reactions

Speaker: Ryotaro Tsuji (University of Tokyo)

11:10 AMD Study of Intruder-Driven Mirror Energy Differences in 29Cl and 29Mg

Intruder configurations can strongly influence mirror energy differences (MEDs) in nuclei near the island of inversion. We study the 29Mg-29Cl mirror pair using antisymmetrized molecular dynamics (AMD), focusing on how intruder configurations affect the MEDs. The calculated spectrum describes both normal and intruder configurations in 29Mg and leads to new spin-parity assignments for the low-lying resonances of proton-unbound 29Cl. A clear contrast is found between the positive- and negative-parity states: the 1/2+ and 3/2+ states show relatively small MEDs, whereas the intruder 3/2- and 7/2- states undergo substantial energy lowering in 29Cl. Analysis of the Coulomb contribution shows that this behavior is associated with enhanced deformation and extended proton distributions of the intruder states, which reduce their Coulomb energies.

Speaker: Mr Dae Ik Kim (Pusan National University)

11:40 → 13:10 Lunch break

13:10 → 14:40 28th Afternoon session 1 (Chair: C. Bertulani)

13:10 How much of spectroscopic quenching belongs to the reaction model?

Speaker: Jin Lei (Tongji U)

13:40 Exact treatment of continuum couplings in nuclear optical potentials via feshbach theory

Speaker: Hao Liu (Tongji University)

14:10 Theoretical Description of Knockout Reactions Involving Unbound Clusters

Speaker: Shoya Ogawa (Kyushu university)

14:40 → 15:00 Coffee break

15:00 → 16:30 28th Afternoon session 2 (Chair: V. Panin)

15:00 First spectroscopy of 100Sn

Nuclear magic numbers arise from large energy gaps between single-particle orbitals and are a defining feature of nuclear structure. When both proton $(Z)$ and neutron $(N)$ numbers coincide with these values, doubly magic nuclei are formed, which provide valuable benchmarks for our understanding of how the strong force arranges nuclei. However, the strength of the shell closures can vary significantly, particularly far from stability. The nucleus $^{100}$Sn $(Z=N=50)$ is the heaviest bound system with equal numbers of protons and neutrons and represents the last doubly magic system along the $Z=N$ line. It serves as valuable testing ground for proton-neutron symmetry at the edge of nuclear existence, where Coulomb repulsion nearly balances the short-range nuclear attraction for the least-bound protons at the Fermi energy. Here we report the first in-beam $\gamma$-ray spectroscopy of $^{100}$Sn. We observed a high-energy transition near 4 MeV, which we assigned to the decay of the first $2^+$ state to the ground state. This excitation energy is among the highest observed in heavy nuclei, comparable to those of established doubly magic nuclei such as $^{132}$Sn and $^{208}$Pb, and significantly larger than the corresponding values in $^{56}$Ni and $^{78}$Ni. These findings demonstrate that $^{100}$Sn exhibits an exceptionally strong $Z=N=50$ shell closure, establishing the robustness of magicity near the proton drip line and providing a stringent test of modern descriptions of nuclear structure.

Speaker: Liu Xiaoyu (The University of Hong Kong)

100Sn.pdf

15:30 Disappearance of the $N=8$ Shell Closure from a Single-Particle Perspective

Speaker: Jie Chen (Southern University of Science and Technology)

16:00 Investigating structural properties of neutron-rich Boron isotopes via QFS reactions

Speaker: Nikhil Mozumdar (Technische Universität Darmstadt)

Tuesday 29 September

09:30 → 10:30 29th Morning session 1 (Chair: T. Uesaka)

09:30 QFS and connection to neutrino physics

Speaker: Seisho Abe (University of Tokyo)

QFS_neutrino_260929_v4.pdf

10:00 (p,pN) studies with spin measurements at intermediate energies

Speaker: Tetuo Noro (none)

10:30 → 10:50 Coffee break

10:50 → 12:20 29th Morning session 2 (Chair: M. Kimura)

10:50 From alpha clustering to alpha decay

Speaker: Dr Zaihong Yang (Peking University)

11:20 Quasi-Free Alpha Clusters Knockout Measurement in Ca Isotopes

Speaker: JICHAO ZHANG

11:50 α cluster formation in the ground state of 16O probed by alpha knockout reaction

Speaker: Taichi Miyagawa (RCNP)

12:20 → 13:50 Lunch break

13:50 → 15:05 29th Afternoon session 1 (Chair: S. Terashima)

13:50 Two-nucleon removal quasifree reactions and their relation to NN correlations

Speaker: Mario Gómez Ramos (Universidad de Sevilla)

14:20 Study of Short-Range Correlations in Stable and Neutron-Rich Nuclei at R³B (Combined talk with M. Xarepe, 45 min. in total)

The formation of short-range correlated nucleon-nucleon pairs (SRCs), primarily composed of neutron-proton pairs [1], appears to be a universal feature in atomic nuclei [2]. Interestingly, measurements in electron scattering indicate that protons become significantly more correlated in asymmetric nuclei as a function of neutron excess This has potential implications for the description of cold dense nuclear matter as for neutron stars. However, data have been so far restricted to stable nuclei for which the N/Z asymmetry, at maximum ~1.6, is strongly correlated to the mass number, leaving open the question of the origin of the evolution of proton-neutron short range correlations with N/Z. To overcome this ambiguity, we performed an experiment at the R³B setup at GSI-FAIR [3] as part of the FAIR Phase-0 experimental program to measure SRC in the most neutron-rich nucleus yet, 16C, with N/Z=1.67, that is slightly larger than the one of 208Pb (1.53). We employ hard proton knockout reactions in inverse kinematics of 16C beam at 1.25 GeV/nucleon, as well as 12C beam as reference, to study SRC behavior. In this talk, we will discuss the final results of the SRC behavior investigation in stable and neutron-rich nuclei (12C and 16C) based on the study of kinematical variables and comparison with INCL and GCF based calculations [4;5].

[1] R. Subedi, R. Shneor, Science, 1156675, 2008.
[2] M. Duer et al. (CLAS Collaboration), Nature, 560:617, 2018.
[3]https://www.gsi.de/work/forschung/nustarenna/nustarenna_divisions/kernreaktionen/activities/r3b.
[4] T. Berggren and H. Tyren. Quasi-free scattering. Annual Review of Nuclear Science, 16:153–182, 1966.
[5] Ronen Weiss and Nir Barnea. Contact formalism for coupled channels. Phys. Rev. C, 96:041303, Oct 2017

Speaker: Andrea Lagni (TU Darmstadt)

14:43 Study of Short-Range Correlations in Stable and Neutron-Rich Nuclei at R³B (Combined talk with A. Lagni, 45 min. in total)

The formation of short-range correlated nucleon-nucleon pairs (SRCs), primarily composed of neutron-proton pairs [1], appears to be a universal feature in atomic nuclei [2]. Interestingly, measurements in electron scattering indicate that protons become significantly more correlated in asymmetric nuclei as a function of neutron excess This has potential implications for the description of cold dense nuclear matter as for neutron stars. However, data have been so far restricted to stable nuclei for which the N/Z asymmetry, at maximum ~1.6, is strongly correlated to the mass number, leaving open the question of the origin of the evolution of proton-neutron short range correlations with N/Z. To overcome this ambiguity, we performed an experiment at the R³B setup at GSI-FAIR [3] as part of the FAIR Phase-0 experimental program to measure SRC in the most neutron-rich nucleus yet, 16C, with N/Z=1.67, that is slightly larger than the one of 208Pb (1.53). We employ hard proton knockout reactions in inverse kinematics of 16C beam at 1.25 GeV/nucleon, as well as 12C beam as reference, to study SRC behavior. In this talk, we will discuss the final results of the SRC behavior investigation in stable and neutron-rich nuclei (12C and 16C) based on the study of kinematical variables and comparison with INCL and GCF based calculations [4;5].

[1] R. Subedi, R. Shneor, Science, 1156675, 2008.
[2] M. Duer et al. (CLAS Collaboration), Nature, 560:617, 2018.
[3]https://www.gsi.de/work/forschung/nustarenna/nustarenna_divisions/kernreaktionen/activities/r3b.
[4] T. Berggren and H. Tyren. Quasi-free scattering. Annual Review of Nuclear Science, 16:153–182, 1966.
[5] Ronen Weiss and Nir Barnea. Contact formalism for coupled channels. Phys. Rev. C, 96:041303, Oct 2017

Speaker: Manuel Xarepe (Technische Universität Darmstadt)

15:05 → 15:25 Coffee break

15:25 → 16:25 Memorial session for Prof. Toshio Kobayashi. Talks by I. Tanihata and H. Otsu (Chair: Y. Kubota)

18:30 → 20:30 Banquet

Wednesday 30 September

09:30 → 10:30 30th Morning session 1 (Chair: Y. Kim)

09:30 Finite-size effects of the α particle in mean-field calculations of α-removal amplitudes

Speaker: Nobuo HINOHARA (Center for Computational Sciences, University of Tsukuba)

10:00 Effect of isoscalar pairing on structure of deuteron-like clusters in nuclei

Speaker: Taishi Ochi (University of Tsukuba)

10:30 → 10:50 Coffee break

10:50 → 12:20 30th Morning session 2 (Chair: C.S. Lee)

10:50 Probing nucleon-nucleon correlations in atomic nuclei via the (p,pd) QFS reactions at R3B

Speaker: Stefanos Paschalis (University of York)

11:20 Study of the short range behavior via (p,pd) with quasi-free kinematics

Speaker: Satoru Terashima (Institute of Modern Physics)

11:50 Nuclear Shell structure governs nucleon Pairing at Short distance

Speaker: Dien Nguyen (University of Tennessee, Knoxville, TN, USA)

12:20 → 13:50 Group Photo and Lunch Break

13:50 → 15:20 30th Afternoon session 1 (Chair: Z. Yang)

13:50 Cluster-shell interplay in nuclear systems

Speaker: Naoyuki Itagaki (Osaka Metropolitan University)

14:20 Cluster formation in the ground states

Speaker: Masaaki Kimura (RIKEN Nishina Center)

14:50 Probing the Ground-State Cluster Structure of 12Be via the Quasifree (p,p\alpha) Reaction

Speaker: Dr Pengjie Li (Fudan University)

15:20 → 15:40 Coffee break

15:40 → 16:40 30th Afternoon session 2 (Chair: Ogawa)

15:40 Search for halos at the proton dripline

Speaker: Carlos Bertulani (Texas A&M University-Commerce)

16:10 QFS studies with neutron-rich fluorine isotopes at R3B

Speaker: Valerii Panin (GSI, Darmstadt)

Thursday 1 October

09:30 → 15:30 Excursion: Excursion to Shirakawa-go (please gather at the entrance of the workshop site Takayama Municipal Cultural Hall at 9:30 a.m.)

Friday 2 October

09:30 → 10:30 2nd Morning session 1 (Chair: Mario Gómez Ramos)

09:30 Green's function calculations for nuclear structure and reactions

Speaker: Stefano Brolli (Università degli Studi di Milano and INFN - Sezione di Milano)

10:00 Analyzing Knockout Reactions Using a Dispersive Optical Model

Speaker: Mack Atkinson (Haverford College)

10:30 → 10:50 Coffee break

10:50 → 11:50 2nd Morning session 2 (Chair: Y. Kondo)

10:50 A universal three-body s-wave resonance in 10He

Speaker: Yelei Sun (Beihang University)

11:20 The search of the tetra-neutron isobaric analog state in the hydrogen-4 system

Speaker: Quentin Délignac (IJCLab / CNRS)

11:50 → 12:00 Closing

11:50 Closing