MondayTuesdayWednesdayThursdayFridayPostersAbstracts
Plenary lectures (all invited) 30 + 5 min · invited talks 20 + 5 min · contributed talks 15 + 5 min. All times CEST. Talk titles in blue link to the abstract at the bottom of this page.
Halls: plenary lectures in HALL 217, Willenberg (2nd floor). Parallel sessions: Session I — HALL 217, Willenberg (2nd floor), Session II — HALL 319, Křižík (3rd floor), Session III — HALL 417, Kašpar (4th floor). Halls are numbered by floor. Refreshments are served on the 2nd floor.
| Sunday, August 16 16:00–19:00 |
Registration & Welcome refreshment The registration desk will then remain open throughout the conference during the programme hours. |
Monday, August 17 |
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| 8:40–9:00 | Opening Ceremony Nina Shevchenko (EFB26 chair) Ondřej Svoboda (NPI CAS, director) Zdeněk Doležal (MFF CU, vice dean) |
| Plenary Session — invited lectures · HALL 217, Willenberg (2nd floor) | 9:00–10:45 |
| 9:00–9:35 | From chiral two- and three-nucleon forces to few- and many-body nuclear phenomena Andreas Ekström (theory) Chalmers University, Gothenburg, Sweden |
| 9:35–10:10 | Ab Initio Theory of Nuclear Structure and Reactions Petr Navrátil (theory) TRIUMF, Vancouver, Canada |
| 10:10–10:45 | The Three-Body Force: Unleashing universality Ubirajara van Kolck (theory) ECT*, Trento, Italy |
| 10:45–11:15 | Coffee break (refreshments on the 2nd floor) |
| Plenary Session (continued) — invited lectures · HALL 217, Willenberg (2nd floor) | 11:15–13:00 |
| 11:15–11:50 | Overview of experiments in the three nucleon system Izabela Skwira-Chalot (exp) University of Warsaw, Poland |
| 11:50–12:25 | Quantum entanglement in NN and Nd scattering Roman Skibiński (theory) Jagiellonian University, Krakow, Poland |
| 12:25–13:00 | MAGIX at MESA: Precision low-energy electron scattering for few-body, nuclear physics, and beyond Sören Schlimme (exp) JGU Mainz, Germany |
| 13:00–14:30 | Lunch break |
| Parallel Sessions — Block 1 | 14:30–16:20 |
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| 16:20–16:50 | Coffee break (refreshments on the 2nd floor) |
| Parallel Sessions — Block 2 | 16:50–18:40 |
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Tuesday, August 18 |
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| Plenary Session — invited lectures · HALL 217, Willenberg (2nd floor) | 9:00–10:45 |
| 9:00–9:35 | The Convergent Close-Coupling method for solving Coulomb few-body problems Igor Bray (theory) Curtin University, Perth, Australia |
| 9:35–10:10 | Neural-network quantum states for few- and many-body systems Alessandro Lovato (theory) IFIC Valencia, Spain |
| 10:10–10:45 | Selected Advances in (Nuclear) Quantum Continuum Physics: Ab Initio Methods and Emulators Xilin Zhang (theory) FRIB, MSU, East Lansing, United States |
| 10:45–11:15 | Coffee break (refreshments on the 2nd floor) |
| 11:15–12:30 | Poster Jamboree |
| 12:30–14:00 | Lunch break |
| Parallel Sessions — Block 1 | 14:00–15:50 |
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| 15:50–16:20 | Coffee break (refreshments on the 2nd floor) |
| Parallel Sessions — Block 2 | 16:20–17:45 |
| 17:45–19:00 | Poster Session (with refreshments) |
Wednesday, August 19 |
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| 8:45–9:00 | “Few-Body Systems Award 2025 for young professionals” ceremony |
| Plenary Session — invited lectures · HALL 217, Willenberg (2nd floor) | 9:00–10:45 |
| 9:00–9:35 | Three-Baryon Femtoscopy as an Effective 3→3 Scattering Experiment (FBS Award) Laura Šerkšnytė (exp) CERN, Geneva, Switzerland |
| 9:35–10:10 | A study of bound state and resonance phenomena in atomic and nuclear few-body systems (FBS Award) Michael Higgins (theory) UMass Boston, United States |
| 10:10–10:45 | Measurement of radiative emission in the d + t → α + n + γ fusion reaction Andrea Dal Molin (exp) University of Milano-Bicocca, Milan, Italy |
| 10:45–11:15 | Coffee break (refreshments on the 2nd floor) |
| Plenary Session (continued) — invited lectures · HALL 217, Willenberg (2nd floor) | 11:15–13:00 |
| 11:15–11:50 | Chiral Symmetry Preserving Nuclear Forces Hermann Krebs (theory) Ruhr University Bochum, Germany |
| 11:50–12:25 | Effective field theory on the lattice Dean Lee (theory) Michigan State University, East Lansing, United States |
| 12:25–13:00 | Bound States and Resonances in a Box (and beyond) Sebastian König (theory) NC State University, Raleigh, United States |
| 13:00–14:30 | Lunch break |
| from 14:30 | Excursions (advance sign-up required via the dedicated form in the registration system) |
| [A] | Cyclotron U-120M — Nuclear Physics Institute (ÚJF), Řež |
| [B] | Tandetron — Nuclear Physics Institute (ÚJF), Řež |
| [C] | Research nuclear reactor LR-0 — Nuclear Research Institute (ÚJV), Řež |
| [D] | Nuclear museum and bunker — Nuclear Research Institute (ÚJV), Řež |
| [E] | Silicon pixel and strip detector lab — MFF of Charles University, Campus Troja, Prague |
| [F] | Van de Graaff accelerator lab — Institute of Applied and Experimental Physics (CTU), Campus Troja, Prague |
| [G] | Prague Walking Sightseeing Tour |
| 19:00 | Conference dinner "Art Restaurant Mánes" |
Thursday, August 20 |
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| Plenary Session — invited lectures · HALL 217, Willenberg (2nd floor) | 9:00–10:45 |
| 9:00–9:35 | Few-body femtoscopy by STAR Ashutosh Pandey (exp) Warsaw University of Technology, Poland |
| 9:35–10:10 | Can the strong interactions between hadrons be determined using femtoscopy? Evgeny Epelbaum (theory) Ruhr University Bochum, Germany |
| 10:10–10:45 | Few-body nuclear systems with an antikaon Tadashi Hashimoto (exp) RIKEN, Wako, Japan |
| 10:45–11:15 | Coffee break (refreshments on the 2nd floor) |
| Plenary Session (continued) — invited lectures · HALL 217, Willenberg (2nd floor) | 11:15–13:00 |
| 11:15–11:50 | First X-ray Measurement of Kaonic Deuterium: A Milestone for Low-Energy Strong-Interaction Studies in the Strangeness Sector Francesco Sgaramella (exp) INFN-LNF, Frascati, Italy |
| 11:50–12:25 | Light hypernuclei Andreas Nogga (theory) FZ Jülich, Germany |
| 12:25–13:00 | High-precision decay-pion spectroscopy of light Lambda hypernuclei at MAMI Patrick Achenbach (exp) JGU Mainz, Germany |
| 13:00–14:30 | Lunch break |
| Parallel Sessions — Block 1 | 14:30–15:55 |
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| 15:55–16:25 | Coffee break (refreshments on the 2nd floor) |
| Parallel Sessions — Block 2 | 16:25–17:50 |
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Friday, August 21 |
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| Plenary Session — invited lectures · HALL 217, Willenberg (2nd floor) | 9:00–10:45 |
| 9:00–9:35 | Precision studies of the molecular hydrogen ions — a testing ground for fundamental interactions Stephan Schiller (exp) HHU Düsseldorf, Germany |
| 9:35–10:10 | Stabilisation of few-body resonances to bound states in a continuum Pascal Naidon (theory) RIKEN, Wako, Japan |
| 10:10–10:45 | Experimental studies of Efimov physics in ultracold atoms Lev Khaykovich (exp) Bar-Ilan University, Ramat Gan, Israel |
| 10:45–11:15 | Coffee break (refreshments on the 2nd floor) |
| Plenary Session (continued) — invited lectures · HALL 217, Willenberg (2nd floor) | 11:15–13:00 |
| 11:15–11:50 | Positron and Positronium Interactions with Atoms and Molecules Gleb Gribakin (theory) Queen's University Belfast, United Kingdom |
| 11:50–12:25 | Antihydrogen studies Stefan Eriksson (exp) Swansea University, United Kingdom |
| 12:25–13:00 | Ultracold chemistry as a testbed for few-body physics Tijs Karman (theory) Radboud University, Nijmegen, Netherlands |
| 13:00–13:15 | Closing of the Conference |
| from 13:15 | Lunch — End of Conference |
List of Posters |
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Dedicated poster slots: Poster Jamboree (Tuesday 11:15–12:30) and Poster Session (Tuesday 17:45–19:00).
| P1 · Giulia Marcer ISTP-CNR, Milan, Italy |
Role of the ⁵He nuclear structure in the limitations of gamma-ray diagnostics for fusion power monitoring in tokamaks |
| P2 · Yan Kostylenko Akhiezer ITP, KIPT, Kharkiv, Ukraine |
Clothed-particle eigenstate problem with 2N and 3N quasipotentials |
| P3 · Daichi Takahashi Science Tokyo, Meguro, Japan |
Polarized solid proton target for spin correlation coefficients measurement of deuteron–proton elastic scattering at 100 MeV/nucleon |
| P4 · Shuhei Ohno Yokohama City University, Japan |
Software Testing in Few-Body Systems Physics |
| P5 · Hiroki Sugahara Science Tokyo, Japan |
Preparing a Polarized Deuteron Beam for the Measurement of Spin-Correlation Coefficients in Deuteron–Proton Elastic Scattering at 100 MeV/nucleon |
| P6 · Hamid Reza Hamedi Vilnius University, Lithuania |
Propagation of optical vector vortices in coherently prepared media |
| P7 · Pavel Belov University of Rostock, Germany |
Bound-state energies of the three-body Coulomb systems in bulk semiconductors |
| P8 · Brady Martin University of Iowa, Iowa City, United States |
The clothing procedure using a φ³ interaction on the light front |
| P9 · Michał Suchorowski University of Warsaw, Poland |
From Scale Invariance to Universal Droplets: Generalised GPE for Attractive 2D Bose Gases |
| P10 · Juraj Fedor Heyrovský Institute, CAS, Prague, Czechia |
Dynamics of electron–molecule resonances probed by 2D electron-energy-loss spectroscopy |
| P11 · Zohar Amitay Technion, Haifa, Israel |
Coherent Control of Ultrafast Molecule Making from a Pair of Atoms |
| P12 · Martin Crhán | Molecular R-matrix approach: from few-body systems to collective processes in multi-electron molecules |
| P13 · Denisa Trnková NPI CAS, Rez, Czechia |
Photoproduction of eta prime mesons off protons in the resonance region |
| P14 · Yubing Dong IHEP, Chinese Academy of Sciences, China |
A study of the electromagnetic and gravitational form factors of nucleon and Δ(1232). |
Abstracts |
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From chiral two- and three-nucleon forces to few- and many-body nuclear phenomena
Andreas Ekström · Monday, August 17 / plenary
Andreas Ekström · Monday, August 17 / plenary
A central challenge in nuclear physics is deriving two- and three-nucleon forces, consistently with low-energy quantum chromodynamics, and understanding how they give rise to the rich phenomena observed in few- and many-body systems. In this talk, I review recent advances in constructing nuclear forces from chiral effective field theory, with Bayesian methods and emulator-accelerated techniques for uncertainty quantification playing a central role. I discuss recent insights to how these forces shape the properties of few-body systems, electromagnetic moments, collective behavior, and the limits of nuclear binding.
Ab Initio Theory of Nuclear Structure and Reactions
Petr Navrátil · Monday, August 17 / plenary
Petr Navrátil · Monday, August 17 / plenary
First-principles (or ab initio) methods that solve the quantum many-nucleon problem with controlled approximations based on validated chiral nucleon-nucleon and three-nucleon forces are currently the best path to achieving a predictive theory of nuclear structure, low-energy scattering and reactions between nuclei. Among them, the ab initio no-core shell model with continuum (NCSMC) [1,2], capable of describing bound and unbound states in light nuclei in a unified way, enabled a wide range of ab initio calculations for weakly-bound halo states, nucleon and lightprojectile-induced capture and fusion reactions. I will review recent applications of NCSMC to structure of halo nuclei, nucleon scattering and radiative capture, charge exchange and transfer reactions on light nuclei. I will highlight calculations of reactions important for astrophysics, fusion energy generation, and searches for physics beyond the standard model. Supported by the NSERC Grant No. SAPIN-2022-00019. TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada. Computing support came from an INCITE Award on the Summit supercomputer of the Oak Ridge Leadership Computing Facility (OLCF) at ORNL, from the Digital Research Alliance of Canada, and from the LLNL institutional Computing Grand Challenge Program. References [1] S. Baroni, P. Navratil, and S. Quaglioni, Phys. Rev. Lett. 110, 022505 (2013); Phys. Rev. C 87, 034326 (2013). [2] P. Navratil, S. Quaglioni, G. Hupin, C. Romero-Redondo, A. Calci, Physica Scripta 91, 053002 (2016).emphasized text
The Three-Body Force: Unleashing universality
Ubirajara van Kolck · Monday, August 17 / plenary
Ubirajara van Kolck · Monday, August 17 / plenary
The traditional approach to few-body physics starts from a sophisticated two-body potential containing many parameters, with few-body forces an afterthought – if a thought at all. In contrast, the renormalization group (RG) tells us that the relative importance of few-body forces depends on the chosen resolution scale. For systems of bosons or multicomponent fermions, a three-body force on an RG limit cycle is essential at the coarsest resolution used to describe the two-body unitarity limit where the S matrix is −1. The gross properties of many-body systems are then governed by discrete scale invariance and universal, when expressed in terms of the single three-body-force parameter. Increasingly accurate results can be obtained in a systematic expansion akin to the multipole expansion in classical electrodynamics. As examples, I consider 4 He atomic clusters and nuclei.
Overview of experiments in the three nucleon system
Izabela Skwira-Chalot · Monday, August 17 / plenary
Izabela Skwira-Chalot · Monday, August 17 / plenary
The study of three-nucleon (3N) systems serves as a fundamental testing ground for our understanding of nuclear interactions, bridging the gap between basic nucleon-nucleon (NN) potentials and the complex dynamics of many-body nuclei. Experiments performed at intermediate beam energies reveal that various dynamical ingredients, such as the three-nucleon force (3NF) and Coulomb force, play an important role in accurately describing observables. High-precision measurements of differential cross sections for elastic scattering and breakup reactions, as well as spin observables like vector and tensor analyzing powers enable rigorous testing of theoretical calculations based on various approaches [1–4] to modeling interactions in three-nucleon systems. Additionally, studies of the 1 H(d, pp)n reaction at relatively low energies are crucial for testing predictions of Chiral Effective Field Theory [5]. The presentation will focus on the effects of the 3NF and the Coulomb force on analyzing power and the differential cross section of the dp breakup reaction, measured over a wide range of energies from 50 to 170 MeV/nucleon [6–10]. Furthermore, information about ongoing projects conducted at the Cyclotron Center Bronowice, PAS, Kraków, Poland, will also be discussed. [1] H. Witała et al., Phys. Rev. Lett. 81 (1998) 1183. [2] A. Deltuva et al., Phys. Rev. C 68 (2003) 024005. [3] S.A. Coon et al., Few-Body Syst. 30 (2001) 131. [4] A. Deltuva et al., Phys. Rev. C 80 (2009) 064002. [5] E. Epelbaum et al., Eur. Phys. J. A 19 (2004) 125; ibid. A 19 (2004) 405. [6] E. Stephan et al., Eur. Phys. J. A 49 (2013) 36. [7] I. Skwira-Chalot et al., Few-Body Syst. 65 (2024) 24. [8] W. Parol et al., Phys. Rev. C 102 (2020) 054002. [9] A. Łobejko et al., Few-Body Syst. 65 (2024) 36. [10] B. Kłos et al., Phys. Rev. C 101 (2020) 044001.
Quantum entanglement in NN and Nd scattering
Roman Skibiński · Monday, August 17 / plenary
Roman Skibiński · Monday, August 17 / plenary
Progress in the ability to perform dedicated experiments as well as the increasingly better understanding of nuclear forces opens up the possibility of studying previously unattainable polarization phenomena in nuclear systems. The possibility of performing scattering experiments with measurement of polarization of three particles encourages investigation of the sensitivity of relevant observables to the details of nuclear forces. Extending this for processes with four polarized particles we computed all terms contributing to polarizations and spin correlations of particles in the final state, i.e. not only induced polarizations and correlations resulting from unpolarized scattering, but also contributions from single polarization and correlation transfers from individual polarized incoming particles, and allotment to both quantities stemming from a doubly spin polarized initial state. This will lead us to the study of quantum entanglement in the proton-neutron scattering, the elastic neutron-deuteron scattering and in the deuteron breakup reaction. While for the first two processes only the Bell-like states can be found, for the neutron induced deuteron breakup in specific kinematical configurations and for specific polarizations in the initial state the pure Bell states exist.
MAGIX at MESA: Precision low-energy electron scattering for few-body, nuclear physics, and beyond
Sören Schlimme · Monday, August 17 / plenary
Sören Schlimme · Monday, August 17 / plenary
Precision electron scattering at low momentum transfer provides a powerful tool to investigate few-body systems, nuclear structure, and physics beyond the Standard Model. The Mainz Energyrecovering Superconducting Accelerator at Johannes Gutenberg University Mainz will deliver high-intensity continuous-wave electron beams ideally suited for such studies. The MAGIX experiment combines a windowless supersonic gas-jet target with high-resolution magnetic spectrometers, enabling precision measurements at low momentum transfer and high luminosity. The physics program includes investigations of few-body systems and precision measurements of proton electromagnetic form factors, with extensions to light nuclei. In addition, the experimental conditions provide access to reaction cross sections of astrophysical interest and excellent sensitivity to searches for dark photons in electron-nucleus scattering. In this talk, the MAGIX experiment at MESA and the physics opportunities enabled by precision low-energy electron scattering will be presented.
¹²C, ¹⁶O and their production reactions in near-zero-range Effective Field Theory inspired framework
Elena Filandri · Monday, August 17 / Session I.1
Elena Filandri · Monday, August 17 / Session I.1
The synthesis of carbon and oxygen is a key problem in nuclear astrophysics, as the reactions ³α → ¹²C + γ and ¹²C(α,γ)¹⁶O determine the stellar C/O ratio and strongly impact stellar evolution. A consistent theoretical description of these processes at low energies is challenging due to strong Coulomb effects and the pronounced α-cluster structure of the nuclei involved. In this talk, I present a near-zero-range Effective Field Theory (EFT) inspired approach for α-cluster systems, exploiting the separation of scales between α-particle excitation and low-energy cluster dynamics. Two-body α–α interactions are constructed up to next-to-next-to-leading order and constrained by low-energy scattering data and the ⁸Be resonance. Three- and four-body contact interactions are introduced to reproduce the bound and excited states of ¹²C and ¹⁶O. Preliminary results for the triple-α capture, obtained within an adiabatic approximation, and for the radiative capture reaction ¹²C(α,γ)¹⁶O are discussed. Calculated cross sections, reaction rates, and low-energy astrophysical S factors are compared with available experimental data and existing theoretical studies.
Formation and decay modes of low-lying ¹²C continuum states in a three-α model
Souichi Ishikawa · Monday, August 17 / Session I.1
Souichi Ishikawa · Monday, August 17 / Session I.1
A detailed knowledge of low-energy excited states in the 12 C nucleus plays an important role in studies of various nuclear models and also of astrophysical issues, such as the triple-α process, in which three α-particles in continuum states are fused into a 12 C nucleus in stars. However, there still remain some uncertainties in knowledge of 12 C continuum states: excitation energies, angular momenta, decay widths, etc. In Ref. 1, strength distributions of the electric multipole transitions from the 12 C(0+ 1 ) ground state to 3α continuum states were calculated in 3α model for some combinations of two-α and three-α interaction models. It was found that the strength distributions for a few interaction models are able to reproduce the experimental excitation-energy spectra in the forward 12 C(α, α′ )3α reaction well. To obtain a deeper understanding of low energy 12 C states, in this paper, I will present calculations of energy- and angular distributions of outgoing 3 α-particles in the 12 C(α, α′ )3α reaction. 1 Souichi Ishikawa, Low-energy 12 C continuum states in a three-α model, Phys. Rev. C 112, 014606 (2025). (https://doi.org/10.1103/3rkb-tzr3)
Microscopic cluster model of ⁸Be resonances and astrophysical S factors near the ⁷Li+p and ⁷Be+n thresholds
Yuliya Lashko · Monday, August 17 / Session I.1
Yuliya Lashko · Monday, August 17 / Session I.1
The resonance structure of 8 Be near the p+7 Li threshold is investigated within a microscopic manycluster, many-channel model including the three-cluster configurations 4 He+3 H+p, 4 He+3 He+n, and 4 He+d+d. This framework provides a unified description of the main binary channels 4 He+4 He, p+7 Li, n+7 Be, and d+6 Li, while explicitly accounting for the internal structure and polarization of cluster subsystems, i.e. their deformation in the interaction region. Particular attention is given to the twin resonances with J π = 1+ , 2+ , 3+ , and 4+ , as well as to the negative-parity 1− and 2− states. The 2+ states below the p+7 Li threshold are identified as Feshbach-type resonances produced by coupling of the open 4 He+4 He channel to the closed p+7 Li, n+7 Be, and d+6 Li channels. We demonstrate that cluster polarization plays a critical role in the formation of these twin positive-parity resonance states. In contrast, the 1− and 2− resonances near the n+7 Be threshold are much less sensitive to cluster polarization. The 2− state and the lowest 1− state are associated with neutron scattering on the ground and first excited states of 7 Be, whereas the second 1− resonance is consistent with 3 He scattering on 5 He. We also study the reactions 7 Li(p, α)4 He, 7 Be(n, α)4 He, 7 Be(n, p)7 Li, 6 Li(d, α)4 He, 6 Li(d, p)7 Li, and 6 Li(d, n)7 Be. For the first three reactions, the calculated astrophysical S-factors reproduce both the magnitude and the low-energy behavior of the data within experimental uncertainties. The 6 Li+d channels are underestimated at low energies, consistent with the shifted threshold and the absence of a broad subthreshold 2+ state in the present model. Overall, the results show that a single microscopic many-channel cluster approach can consistently describe both the 8 Be resonance spectrum and the associated low-energy reaction observables.
Alpha Clusters as Efimov States: Universal Few-Body Physics and the Role of Coulomb from ⁸Be to ¹⁶O
Mario Gattobigio · Monday, August 17 / Session I.1
Mario Gattobigio · Monday, August 17 / Session I.1
I present a unified description of alpha-cluster nuclei rooted in the theory of shallow two-body states and its connection to Efimov universality. The starting point is the observation that the space of two-body potentials admits a one-dimensional attractor under renormalization-group flow: all interactions sharing the same low-energy parameters flow, in the regime re /a lesssim0.5, toward the Eckart potential, whose S-matrix has exactly two poles. One pole is the physical near-threshold state; the other acts as an infrared cutoff fixing the resolution scale, playing a role analogous to the three-body parameter in Efimov physics. The α-α system sits precisely inside this window, and the Coulomb repulsion converts the shallow bound state into the narrow 8 Be resonance —the two-body input to everything that follows.
Precise few-body calculations by AI coding
Shigeyoshi Aoyama · Monday, August 17 / Session I.1
Shigeyoshi Aoyama · Monday, August 17 / Session I.1
Recent advancements in generative AI are fundamentally transforming various sectors of society. In scientific research, “AI coding”—the utilization of AI for software development—is garnering significant attention. In large-scale numerical simulations, implementing new algorithms or adding features often requires several months of intensive development. For instance, in fewbody physics, even after a new method is established for a three-body system, extending it to larger systems frequently involves repetitive and complex coding tasks that are prone to human error. Generative AI, which can perform these exhaustive tasks without fatigue, enables the efficient creation of complex few-body calculation codes that were previously difficult to implement manually.In this presentation, we report on the development of a Stochastic Variational Method (SVM) code for a five-body system (4 He pentamer) using the generative AI model, Gemini. We provide a brief overview of the AI-assisted coding process and discuss the results obtained from applying the generated code to the 4 He pentamer.
Resonant states in few-body hypernuclei
Rimantas Lazauskas · Monday, August 17 / Session II.1
Rimantas Lazauskas · Monday, August 17 / Session II.1
Hypernuclei provide a uniquely controlled environment for investigating fundamental baryonic interactions. The incorporation of hyperons into atomic nuclei, together with their relatively weak binding, gives rise to exotic systems that enable detailed studies of both hyperon–nucleon (YN) and hyperon–hyperon interactions. In this presentation, we employ calculations based on realistic nucleon–nucleon and hyperon– nucleon interactions derived from chiral effective field theory to explore the possible existence of resonant states in three- and four-body strangeness S=-1 hypernuclei. Particular attention is devoted to Feshbach resonant states near the Σ-hyperon production threshold. We identify J π = 1/2+ ΣNN and J π = 0+ ΣNNN states, and determine their energies and widths, allowing us to assess their potential observability.
Coulomb-induced K⁻pp molecular state
Tanner Massimino · Monday, August 17 / Session II.1
Tanner Massimino · Monday, August 17 / Session II.1
The K − pp, a three-body system combining Coulomb and strong interactions, poses experimental and theoretical challenges. The theoretical problem is that these interactions operate on vastly different length scales, and the K − p Coulomb interaction supports infinitely many bound states. We studied the K − pp system with both interactions being active and found that this combined three-body system has an not only the quasi-bound state caused mainly by the strong antikaonnucleon interaction, but also a Coulomb-induced molecular state. The first one is an extremely compact ground state, while the molecular state is a far more spatially extended excited state of the system. To cope with the Coulombic features, we solve the Faddeev-Merkuriev integral equations. We located both poles on the complex energy plane to find the energies and widths of the decaying three-body system. The strong K − p interaction is represented by a complex separable potential.
Femtoscopic study on Kaon-Nucleus correlation functions
Yuki Kamiya · Monday, August 17 / Session II.1
Yuki Kamiya · Monday, August 17 / Session II.1
In recent years, studies of hadron-hadron interactions using momentum correlations of hadron pairs observed in high-energy collision experiments have been actively conducted. Regarding Kaon-nucleon interactions, K+p/K−p pairs have been observed. It has been confirmed that these momentum correlations can be well described by chiral dynamics models. As a further research method for KN/KbarN interactions using the femtoscopy, there is a method using pair correlations with nuclei. Specifically, since 4He (alpha) is more deeply bound compared to other nuclei, it is thought that K+alpha/K-alpha pairs can be well described as a two-body system, and they have been proposed as candidates for correlation functions. The interactions of these pairs are expected to be useful for the isospin component decomposition of the interactions, as they are given by isospin component ratios different from those of K+p/K−p pairs. In this presentation, we discuss the calculation results of K-alpha correlations using a K−alpha folding potential constructed based on a KbarN chiral dynamics model and a phenomenological optical potential based on K atomic energy level shifts.
Light nuclei with hidden strangeness
Roman Kezerashvili · Monday, August 17 / Session II.1
Roman Kezerashvili · Monday, August 17 / Session II.1
We study light ϕ-mesic nuclei with number of particles A = 2–5 using Faddeev and Faddeev– Yakubovsky equations with QCD-constrained ϕN interactions in the ϕN (2 S1/2 ) and ϕN (4 S3/2 ) spin channels [1]. The ϕN , ϕN N , ϕN N N , and ϕN N N N systems are analyzed under different mass scenarios and varying spin splitting of the ϕN interaction. The bound states in the ϕ-mesic nuclei ϕ4 H, 4ϕ He, and 5ϕ He, where superscript denotes the total number of particles in the system, were predicted. Equivalently, these systems correspond to ϕN N , ϕN N N , and ϕN N N N fewbody configurations with particular spin and isospin. Binding is driven by the strongly attractive ϕN (2 S1/2 ) channel, leading to bound ϕN N , ϕN N N , and ϕN N N N systems, where the ϕ meson acts as a deeply bound impurity and induces compact nuclear configurations. Inelastic effects, included via a complex potential, have little impact on binding energies while producing moderate widths, indicating possible experimental observability. Coulomb shifts of the binding energies are evaluated. The low-energy correlation effects in the ϕ-mesic nuclei are discussed. We find universal correlations between binding energies for A = 2–5, including Tjon-like relations and scaling with the ϕN scattering length (Phillips-like line), demonstrating that these systems are largely governed by two-body physics. Our findings clarify the binding mechanism and the structure of ϕ-mesic nuclei, as well as the role of short-range ϕN interaction. [1] R. Lazauskas, R. Ya. Kezerashvili, and I. Filikhin, Faddeev–Yakubovsky calculations for ϕ-mesic nuclei with HAL QCD potential, Phys. Rev. D \textbf{113}, (2026) in press.
Insights into Λ and Ξ⁻ dynamics with nucleons in ALICE
Georgios Mantzaridis · Monday, August 17 / Session II.1
Georgios Mantzaridis · Monday, August 17 / Session II.1
Understanding the interaction of strange baryons with nucleons is a key ingredient for describing dense baryonic matter, where the appearance of hyperons in the cores of neutron stars is expected to strongly soften the equation of state, hence limiting the maximum stellar mass. New constraints, not only on two-body but also on multi-body hyperonic interactions, are necessary to address this problem. So far, several attempts to include three-body forces have relied on scarce experimental information from hypernuclei, where existing data on Λ hypernuclei are far less precise than theoretical predictions, and only a few Ξ− hypernuclei events have been observed. In this contribution, new high-precision femtoscopic measurements from the ALICE experiment are presented, probing three-body systems containing protons and hyperons via the p-p-Λ and pp-Ξ− correlation functions in pp and Pb-Pb collisions. Preliminary theoretical studies indicate that the effect of three-body forces on the p-p-Λ correlation function could reach 40%, a level achievable with Run 3 statistics. Comparisons across different collision systems and centralities provide information on the extent to which three-body forces can be tested with increasing source size. The coupled-channel nature of p-Ξ− pairs is addressed by confronting recently updated calculations with the p-Ξ− correlation function measured in pp collisions at 13.6 TeV. These results open a new path toward quantifying three-body effects in the strangeness sector, with direct implications for modeling dense nuclear matter and the neutron star equation of state.
Entanglement in few-nucleon scattering events
Tanja Kirchner · Monday, August 17 / Session III.1
Tanja Kirchner · Monday, August 17 / Session III.1
I will quantify the spin entanglement in few-particle scattering (e.g. neutron-proton, neutrondeuteron scattering) using the entanglement power or rather the Taylor approximation of the von Neumann entropy.
The Unitarity Limit With Pions and Entanglement in S-wave NN Scattering
Harald W. Grießhammer · Monday, August 17 / Session III.1
Harald W. Grießhammer · Monday, August 17 / Session III.1
Theorists love the Unitarity Limit, when S-wave scattering lengths are infinite and the number of symmetries is large. For example, there are strong hints that Nuclear Physics resides in a sweet spot: bound weakly enough to be insensitive to the details of the nuclear interaction; but dense enough that the N N scattering lengths are perturbatively close to this nontrivial fixed point. In this paradigm change, details of two-nucleon interactions are less important to explain the complexity and patterns of the nuclear chart than the fact that interactions are strong. This presentation is a digest of the first quantitative exploration of corrections to unitarity from interactions which introduce (microscopic) scales. When pions are included perturbatively, their mass and decay constant provide dimensionful scales, and thus explicitly break the symmetries of the Unitarity Limit. Its leading order is identical to the Effective Field Theory of point-like interactions/”pion-less” EFT. Up to next-to-next-to-leading order, the expansion with perturbative pions describes the N N system well, and unitarity is only broken weakly. Apparent large discrepancies in the 3 S1 channel even at k ≈ 100 MeV are remedied by taking only the central part of the pion’s N2 LO contribution, namely the part invariant under Wigner’s SU(4) group of combined spin-isospin transformations which is also realised in the unitarity limit. This leads to the \emph{Conjecture} that both scale invariance and Wigner-SU(4) symmetry in the Unitarity Expansion show “Persistence”, i.e. the footprint of both combined dominates even for k gtrsimmπ and is more relevant than chiral symmetry. Such an effect appears however absent when pions are included non-perturbatively. I also offer a geometric construction of entanglement in N N S-waves and investigate its role both close to unitarity and in the real world. Work in collaboration with Y.-P. Teng (GW and U. of Wisconsin), N. Carter (GW) and O. Thim (Chalmers U.). Supported in part by US DoE award DE-SC0015393.
Application of symmetry-preserving higher-derivative formulation of baryon ChPT to NN scattering problem
Jambul Gegelia · Monday, August 17 / Session III.1
Jambul Gegelia · Monday, August 17 / Session III.1
Symmetry-preserving higher-derivative formulation of non-relativistic baryon chiral effective field theory, leading to improved ultraviolet behavior, will be briefly discussed. Application to the nucleon-nucleon scattering problem at next-to-leading order will be presented. Generalization for processes involving more nucleons will be touched upon.
Field-theoretical description of the deuteron breakup in the clothed particle representation
Oleksandr Shebeko · Monday, August 17 / Session III.1
Oleksandr Shebeko · Monday, August 17 / Session III.1
Explorations of the deuteron electrodisintegration d(e, e′ p)n have the eventful history, starting from the first coincidence experiments that have been performed in: Stanford, Orsay, Kharkiv, Saclay and continued nowadays at Jefferson Lab. Recent experiments in deuteron electrodisintegration at high momentum transfers, particularly at Jefferson Lab, have pushed deuteron studies into the relativistic region, reaching missing neutron momenta kn up to ∼ 1.0 GeV/c. Under such conditions, a non-relativistic description of the d(e, e′ p)n reaction could be insufficient. In this research, a new field-theoretical approach extends the in(out) formalism by Lehmann, Symanzik and Zimmermann (LSZ) [1], being combined with the clothed particle representation (CPR) [2,3]. We are working in the instant form of relativistic dynamics, where only the total Hamiltonian H and the boost operator B carry interactions. Under this framework, the nucleon-nucleon (NN) interaction, meson-exchange currents (MECs), and boost operators are constructed consistently, ensuring relativistic invariance by satisfying the Poincaré algebra. The electromagnetic current operators used in this work are derived directly from the conserved Noether current of the underlying meson-nucleon field model via its reformulation in terms of clothed particle operators. Within the method of unitary clothing transformation, the same transformation that generates the relativistic NN interaction operator also induces a new family of current operators, so the onebody, two-body (meson-exchange) and other many-body current operators emerge on a common footing. Following our recent work [4], we employ a fully relativistic framework and propose a way towards the gauge-independent treatment. The latter can be achieved by imposing the FockWeyl criterion (details can be found in [5]). We compare our new calculations with the Saclay [6,7] and Jefferson Lab data [8], as well as other theoretical predictions [9,10]. The role of the final state interaction (FSI) and MEC contributions depends on the kinematics. Contrary to the results in the Saclay kinematic regimes, for the higherenergy kinematics of Ref. [8] the FSI and MEC contributions may act constructively and increase the cross section at larger neutron momenta kn . We investigated the effects of various meson exchanges and showed that they partially compensate each other. Overall comparison with the data shows that the relativistic effects are essential. In particular, we demonstrate the role of Fermi motion effects. It is implied that our approach can be extended to the theory of the neutrino scattering off fewnucleon nuclei. References 1. H. Lehmann, K. Symanzik, W. Zimmermann, Nuovo Cim. 1 (1955) 205; 2. O. Greenberg, S. Schweber, Nuovo Cim. 8 (1958) 378; 3. A. Shebeko, M. Shirokov, Phys. Part. Nucl. 32 (2001) 15; 4. Y. Kostylenko, A. Shebeko, Few-Body Syst. 65 (2024) 55; 5. A. Shebeko, PoS Baldin ISHEPP XXII 225 (2015) 027; 6. M. Bernheim et al., Nucl. Phys. A 365 (1981) 349; 7. S. Turck-Chièze et al., Phys. Lett. B 142 (1984) 145; 8. P. Ulmer et al., Phys. Rev. Lett. 89 (2002) 062301; 9. A. Korchin, Yu. Mel’nik, A. Shebeko, Few-Body Syst. 9 (1990) 211; 10. Yu. Mel’nik, A. Shebeko, Few-Body Syst. 13 (1992) 59.
Testing NN EFT with the bootstrap technique
David R. Entem · Monday, August 17 / Session III.1
David R. Entem · Monday, August 17 / Session III.1
We test the accuracy of different approaches performing a bootstrap montecarlo calculation. We consider a toy model in which there is a piece similar to OPE in the 1S0 partial wave, a second piece with a singular interaction of two pion masses range and two short range pieces that make the whole potential regular. We consider the full potential as the solution of the “full theory” and we test the accuracy considering the first and second pieces supplemented by short range components. We do it in two different frameworks. The first one with interactions regulated by a cutoff of 500 MeV supplemented by regulated contact interactions. The second one with the exact N/D method with short range contributions given by subtractions in the N/D equations, which is, in some cases, equivalent to send the cutoff to infinity. We generate pseudo experimental data with Gaussian distributions around the value of the “full theory” and some error for the distribution which gives the accuracy of the experimental data. Then we fit the different approaches to the pseudo data through the unknown short range part. This is done for 2000 experiments. Statistical tests are performed to see when the approach is consistent with a defined accuracy on experimental data. The program is also performed for the NN chiral EFT at LO and NLO with the N/D method using as data the Granada phase-shift analysis for the 1S0 partial wave.
Investigating the Structure and Reactions of Borromean Halos in Z > 8 Systems
Jagjit Singh · Monday, August 17 / Session I.2
Jagjit Singh · Monday, August 17 / Session I.2
The development of advanced Rare Isotope Beam (RIB) facilities has opened new frontiers in exploring neutron-rich nuclei near the drip line. In particular, Borromean halo systems with Z >8 and neutron numbers around the magic numbers N=20 and N=28, as well as those in between, have attracted significant attention [1-11]. In this talk, I will report our recent few-body results on the structure and reactions of Borromean halo nuclei in systems with Z = 9, 11, and 12. The structure is investigated within a three-body (core+n + n) framework using the hyperspherical harmonics method with an analytical transformed harmonic oscillator basis. Key observables such as configuration mixing, matter radii, neutron-neutron correlations, and electric dipole (E1) response will be discussed. On the reaction side, total reaction cross sections are evaluated using the Glauber model. Results will be presented for the heaviest observed two-neutron halo nucleus, 29 F [2-4], along with predictions for candidate halo systems including 31 F [7], 37,39 Na [9,10], and 40 Mg [9,11]. These studies provide insight into the emergence and evolution of Borromean halo structures in medium-mass neutron-rich nuclei. 1 S. Bagchi, et al., Phys. Rev. Lett. 124, 222504 (2020). 2 Jagjit Singh, et al., Phys. Rev. C 101, 024310 (2020). [3] J. Casal, Jagjit Singh, et al., Phys. Rev. C 102, 064627 (2020). [4] L. Fortunato, et al., Commun. Phys. 3, 132 (2020). [5] A. Revel, et al., Phys. Rev. Lett. 124, 152502 (2020). [6] D. S. Ahn, et al., Phys. Rev. Lett. 129, 212502 (2022). [7] G. Singh, Jagjit Singh, et al., Phys. Rev. C 105, 014328 (2022). [8] K.Y. Zhang, et al., Phys. Rev. C 107, L041303 (2023). [9] Jagjit Singh et al., Phys. Lett. B 853, 138694 (2024). [10] Jagjit Singh et al., arXiv:2512.22951 [nucl-th]. [11] Jagjit Singh et al., Acta Phys. Pol. B Proc. Suppl. 19, 1-A9 (2026).
Theory for the extraction of the neutron-neutron scattering length from hard knockout reactions
M. Göbel · Monday, August 17 / Session I.2
M. Göbel · Monday, August 17 / Session I.2
At leading order the neutron-neutron interaction is given by its s-wave scattering length. This important parameter of nuclear physics it is not yet known at the desired accuracy. Up-to-date values range from -16.3(4) fm to -18.7(7) fm. I will talk about how neutron-neutron relative-energy distributions from hard knockout reactions on nuclear few-body systems can help to determine this parameter. Such a reaction could be 6 He(p, p′ α)nn. After knocking out the α core, the neutron pair propagates to the detector. During that final-state interaction between the neutrons take place. Thereby, the neutron-neutron relative-energy distribution to be measured has imprints of the ground-state neutron distribution as well as from the final neutron-neutron interaction. Interaction parameters, such as the scattering length, can be inferred by comparing the experimental spectrum with the theoretical spectrum depending on the parameter of interest. The focus of this talk will be on the theory part which is crucial to this endeavor. I will show how the distribution for the α knockout in 6 He can be obtained [Göbel et al., Phys. Rev. C 104 (2021) 2, 024001]. The basis is the description of the ground state in halo effective field theory, which is a pionless field theory designed to describe halo nuclei. The degrees of freedom are given by the more tightly bound core and the more loosely bound halo neutrons. Using an EFT enables robust uncertainty estimates and the possibility to systematically improve the results. Having the bound state at hand, one can then calculate the final distribution by taking the final-state neutron-neutron interaction into account. Since the knockout is high-energy, the influence of it on the distribution can be neglected at leading order. The sensitivity on the scattering length will be discussed, also in regards to the different sources of the sensitivity. It was found that the distribution is quite sensitive to the variation of the scattering length: varying this parameter by 2 fm changes characteristic parts of the distribution by 10 %. Moreover, I will discuss the reaction t(p, 2p)nn, which can also be used to extract the scattering length [Kirchner et al., Phys. Rev. C 111 (2025) 4, 044002]. The strategy for the theoretical description is similar here. The FSI calculation is analogue and the ground state of the triton is described using pionless EFT. While for 6 He the current calculations are at LO, for triton LO and NLO results will be presented. A similar sensitivity as in the case of 6 He was found. An outlook to an N2LO description is given. For the future it is planned to extend the calculation for 6 He to NLO. In this context, results from current calculations of the E1 strength distribution of 6 He at NLO can be reused.
Feshbach-Villars approach to relativistic few-particle systems
Zoltán Papp · Monday, August 17 / Session I.2
Zoltán Papp · Monday, August 17 / Session I.2
The Feshbach-Villars equation represents a two-component non-Hermitian Hamiltonian form of the relativistic Klein-Gordon equation. The equation is linear in the time derivative and quadratic in the spatial derivatives, and consequently it is also linear in the energy variable. The energies of independent particles are additive, so we can define the few-particle Hamiltonian as a sum of one-particle Feshbach-Villars free Hamiltonians plus interactions that depend on interparticle distances. Moreover, the quadratic spatial derivatives allow us to separate off the center of mass coordinate, and thus allow us to construct a consistent few-particle theory in terms of the Jacobi coordinates. We present solutions for three-quark systems along the Faddeev approach.
Few-body correlation functions with discrete scale invariance
Hans-Werner Hammer · Monday, August 17 / Session I.2
Hans-Werner Hammer · Monday, August 17 / Session I.2
The correlation functions of fermions in the unitary limit are strongly constrained by Schrödinger symmetry, which includes scale invariance. This allows for model-independent predictions of certain hard nuclear reactions with final state neutrons. In systems displaying Efimov physics, such as spinless bosons, the scale invariance is anomalously broken to a subgroup of discrete scaling transformations. In this talk, we discuss the constraints of discrete scale invariance on few-body correlation functions and show some numerical tests.
Universal but not Efimovian few-body resonances
Ludovic Pricoupenko · Monday, August 17 / Session I.2
Ludovic Pricoupenko · Monday, August 17 / Session I.2
Efimov states are well-know examples of universal few-body states that can be observed in the vicinity of the unitary limit. In this regime where there is a clear scale separation between the range of the interactions and the scattering length, other universal states are possible. They appear for sufficiently attractive short-range inter-particle potentials in close analogy with two-body bound states in high-partial waves. Halos nuclei are specific examples of such states but they can also exist in all configurations where the Efimov effect is absent. In this talk, we will show that two few-body parameters are sufficient to describe them. We will consider a class of three-body systems for which exact solutions in a model with zero-range potentials, universal by construction, can be successfully compared to calculations using finite-range potentials, as a function of the scattering length.
Machine learning light hypernuclei
Isaac Vidaña · Monday, August 17 / Session II.2
Isaac Vidaña · Monday, August 17 / Session II.2
We employ a feed-forward artificial neural network (ANN) to extrapolate {\it ab-initio} hypernuclear No-Core Shell Model results for the Λ separation energy BΛ of 3Λ H, 4Λ H, and 4Λ He, obtained using chiral nucleon-nucleon, three-nucleon, and hyperon-nucleon interactions, from computationally accessible harmonic oscillator spaces to large model spaces. Overfitting is controlled by enlarging the input dataset and adding Gaussian noise during the training of the network. A single hidden layer with eight neurons suffices to extrapolate BΛ to Nmax = 100. The results agree with experiment for 3Λ H and the 0+ state of 4Λ He, but differ by about 0.3 MeV for the 0+ and 1+ states of 4Λ H and the 1+ state of 4Λ He. The main goal of this study, however, is to assess the reliability of ANNs for extrapolating No-Core Shell Model results to large model spaces, rather than to optimize agreement with experimental observables. The excellent agreement found with other extrapolation schemes of hypernuclear No-Core Shell Model calculations confirms the reliability of the ANN approach.
Light muonic atoms with artificial neural network
Sonia Bacca · Monday, August 17 / Session II.2
Sonia Bacca · Monday, August 17 / Session II.2
The leading uncertainty in the extraction of charge radii from spectroscopic measurements of light muonic atoms arises from nuclear structure effects. The dominant contribution, driven primarily by the electric dipole operator, can be expressed in terms of energy-weighted integrals over the nuclear response functions. For p-shell nuclei, fully ab initio calculations remain computationally challenging. We therefore develop a complementary, more phenomenological approach based on training artificial neural networks on dipole strength data for nuclei with Z < 20. We benchmark our method against existing hyperspherical harmonics results in the s-shell sector and present new predictions for p-shell nuclei of interest to the QUARTET collaboration at PSI.
Mesonic weak decays of light hypernuclei
Philipp Quoss · Monday, August 17 / Session II.2
Philipp Quoss · Monday, August 17 / Session II.2
Hypernuclei offer a unique window on nuclear matter with strangeness and on the role of strange baryons in nuclei. Among them, Λ-hypernuclei are the most accessible systems and provide an ideal testing ground for these questions. A particularly intriguing question is whether a Λ hyperon changes its lifetime once embedded in a nucleus. In this talk, I present a study of mesonic weak decays of light hypernuclei within a non-relativistic cluster effective field theory. In particular, I consider the light systems 4Λ He, 4Λ H and 5Λ He, focusing on their dominant decay channels and on the role of final-state interactions. The talk will highlight how this framework can help clarify the connection between hypernuclear structure, weak decay, and existing experimental data.
The hyperon-nucleon interaction in a low energy effective field theory
Margherita Sagina · Monday, August 17 / Session II.2
Margherita Sagina · Monday, August 17 / Session II.2
In recent years, there has been a notable interest in investigating hypernuclear systems, which provide a unique laboratory for studying strong interactions in the strange quark sector. One of the main applications is related to the so-called “hyperon puzzle” in neutron stars, where theoretical models including hyperons predict maximum masses of \sim 1.5 M_{\odot} or less, in conflict with observations of neutron stars with masses up to \sim 2 M_{\odot}. Solving this puzzle with nuclear physics tools requires a detailed understanding of hyperon-nucleon (YN) interactions, hyperonhyperon (YY) interactions, and three-body interactions involving hyperons and nucleons. In this talk, I will present the development of a local potential model for the \Lambda N interaction, derived using a low-energy EFT formalism that involves contact terms only. The present interaction has been derived up to next-to-leading order (NLO). I will also discuss the details of the fitting procedure to \Lambda p elastic scattering cross sections and present our results for different cutoff parameters up to 2.5 fm. Finally, I will briefly outline some possible extensions of this framework. These include the generalization to a chiral version of the theory, which would allow for a more systematic treatment of pion exchanges within the EFT hierarchy, as well as the development of Bayesian inference techniques to better constrain low-energy observables such as the \Lambda N scattering length, offering a more rigorous statistical treatment of the model uncertainties.
KN scattering amplitude through a separable potential
Dimitrios Petrellis · Monday, August 17 / Session II.2
Dimitrios Petrellis · Monday, August 17 / Session II.2
We analyze the K + -nucleon interaction using a separable potential and the relativistic LippmannSchwinger equation in momentum space 1. Parameters of the potential are fitted to the real and imaginary parts of the KN T matrix obtained from a previous partial wave analysis 2 and to the total cross sections. We use statistical learning techniques both in the fitting, as well as in estimating parameter uncertainties. The aim of this work is to provide a new momentum-space K+ -nucleon amplitude which can be used in constructing the optical potential in kaon-nucleus scattering [3] and to include kaon distortion in the DWIA calculations of the cross sections in electroproduction of hypernuclei [4]. References 1 P. Bydžovský and M. Sotona, Separable model for K+ -nucleon scattering, In Proc. 7th Conf. on Mesons and Light Nuclei, Praha-Pruhonice, Czech Republic, 31 Aug. - 4 Sept., 1998, World Scientific, Singapore, 1999, p. 138. 2 John S. Hyslop, Richard A. Arndt, L. David Roper, and Ron L. Workman, Partial-wave analysis of K+ -nucleon scattering, Phys. Rev. D 46, 961 (1992). [3] P. Bydžovský and M. Sotona, Momentum-space optical model for K+ -nucleus scattering, Czechoslovak Journal of Physics, 48, 903 (1998); Elastic Scattering of K+ from Light Nuclei, In Proc. 6th Conf. on Mesons and Light Nuclei, Straž pod Ralskem, Czech Republic, July 3 - 7, 1995, Few Body Systems Suppl. 9, 61 (1996). [4] P. Bydžovský, D. Denisova, D. Skoupil, and P. Veselý, Phys. Rev. C 106, 044609 (2022); P. Bydžovský, D. Denisova, D. Petrellis, D. Skoupil, P. Veselý, G. De Gregorio, F. Knapp, and N. Lo Iudice, Phys. Rev. C 108, 024615 (2023); P. Bydžovský, D. Denisova, F. Knapp, and P. Veselý, Phys. Rev. C 112, 024609 (2025).
Heavy and heavy-light tensor and axial-tensor mesons in the Covariant Spectator Theory
Alfred Stadler · Monday, August 17 / Session III.2
Alfred Stadler · Monday, August 17 / Session III.2
We present the first calculations of the masses of heavy and heavy–light tensor and axial-tensor mesons with total angular momentum up to J=3, obtained within the Covariant Spectator Theory (CST). This fully relativistic Minkowski-space framework describes the quark–antiquark interaction through a one-gluon-exchange plus a covariant generalization of a linear confining potential. The CST formalism, which in the past has been applied successfully to heavy and heavy–light mesons with J P = 0± and 1± , is here extended to arbitrary spin-parity J P . Our model involves a small set of parameters, determined from global fits to the measured spectra up to J = 3. Our results provide a very good description of the existing experimental data and predict some yet unobserved states. These predictions may guide future experimental searches at facilities such as LHCb and Belle II. Furthermore, the model offers a systematic framework for analyzing the partialwave compositions, and for assigning quantum numbers to still undetermined quark–antiquark states listed in the PDG. It also contributes to the identification of possible non–-quark-antiquark configurations.
Electromagnetic properties of the nucleon from the instanton vacuum
Hui-Jae Lee · Monday, August 17 / Session III.2
Hui-Jae Lee · Monday, August 17 / Session III.2
We present recent results on the electromagnetic properties of nucleons, obtained within an effective chiral theory derived from the QCD instanton vacuum. A key advantage of this framework is that it contains no adjustable parameters; moreover, the momentum-dependent dynamical quark mass serves as a natural ultraviolet regularization of divergent quark-loop integrals. We employ the pion mean-field approach, in which the nucleon is described as a bound state of Nc valence quarks with the polarized Dirac sea in the self-consistent manner. We compute the electric and magnetic form factors of the proton and neutron, together with related electromagnetic observables, and compare the results with those of the local chiral quark-soliton model, in which the dynamical quark mass is taken to be constant. The present framework yields a improved description of the Q2 dependence of the electromagnetic form factors for both the proton and the neutron. In particular, the ratio µp GpE /GpM , whose deviation from unity has been firmly established by polarization-transfer experiments, is well reproduced without additional parameter tuning.
Instanton Effects on Quark Orbital Angular Momentum in the Nucleon
Jun-Young Kim · Monday, August 17 / Session III.2
Jun-Young Kim · Monday, August 17 / Session III.2
Instantons provide a mechanism for chiral symmetry breaking that turns low-energy QCD into an effective theory of massive constituent quarks with chiral spin-flavor interactions. Within the same framework, QCD operators involving gauge fields can be mapped onto corresponding operators in the effective theory. In this work, we investigate instanton effects in the twist-3 quark energy-momentum tensor and their implications for the decomposition of quark angular momentum into spin and orbital contributions.
Tensor properties of the nucleon in a pion mean-field approach
Nam-Yong Ghim · Monday, August 17 / Session III.2
Nam-Yong Ghim · Monday, August 17 / Session III.2
The tensor form factors of the nucleon provide essential information for understanding its internal spin structure. The monopole tensor form factor at Q2 = 0 is identified as the nucleon tensor charge, which corresponds to the first moment of the leading-twist transverse parton distribution function h1 (x). While transversity has been extensively studied both theoretically and experimentally, other tensor form factors have received much less attention. In this talk, we present recent results for the nucleon multipole tensor form factors calculated within the pion mean-field theory. The framework is based on the effective dynamics arising from spontaneous chiral symmetry breaking and the mean-field description of the nucleon at leading order in the large-Nc limit. We find that the tensor charge (gTu−d = 0.99) and the tensor anomalous magnetic moment (κu+d = 7.61) are dominated by valence quark contributions, whereas the tensor quadrupole T moment (Qu−d = −7.02) shows significant sea quark effects. We also explore the dependence T of these moments on the soliton size and the pion mass, observing a smooth transition between non-relativistic and relativistic regimes. The results agree well with available lattice QCD data and provide predictions for unmeasured quantities.
Mass splitting of doubly heavy baryons
Hyun-Chul Kim · Monday, August 17 / Session III.2
Hyun-Chul Kim · Monday, August 17 / Session III.2
We present the results from a recent work on the mass spectrum of doubly heavy baryons in a pion mean-field approach. We first focus on the isospin mass splitting of doubly heavy baryons, considering both the hadronic and electromagnetic contributions. We obtain MΞ++ − MΞ + = cc cc (1.43 ± 0.38) MeV, which is in remarkable agreement with the recent LHCb data. Taking the measured mass of the Ξ++ = (3749.15 ± 3.31) MeV. We cc as input, we are able to predict MΩ+ cc discuss a possible interpretation of doubly heavy baryons as qualitons.
The Convergent Close-Coupling method for solving Coulomb few-body problems
Igor Bray · Tuesday, August 18 / plenary
Igor Bray · Tuesday, August 18 / plenary
The Coulomb few-body problem that is electron scattering on atomic and molecular targets is difficult to calculate due to the targets’ countably infinite discrete spectrum and its uncountably infinite continuum. Furthermore, at energies above the ionisation threshold we have at least three charged particles interacting out to infinite distances via the long-ranged Coulomb potential. The Convergent Close-Coupling method addresses these problems via the usage of a truncated complete Laguerre basis used to expand the target-state wavefunctions. This induces an equivalent quadrature rule for the full target spectrum, using a finite number N of square-integrable target states, when expanding the total wavefunction of the electron-target system. Such an expansion also ensures that only one electron ever escapes to true infinity. The big question is: does such an approach yield convergence in the scattering amplitudes of interest with increasing N, and if so, is the convergence to the right answer. We shall show that the answer is yes to both of these questions for discrete excitation and even for fully differential ionisation.
Neural-network quantum states for few- and many-body systems
Alessandro Lovato · Tuesday, August 18 / plenary
Alessandro Lovato · Tuesday, August 18 / plenary
Solving the quantum many-body problem entails nontrivial difficulties stemming from the exponential growth of the Hilbert-space dimension. Artificial neural networks have proven to be flexible tools for compactly representing quantum many-body states. I will present a variational Monte Carlo method based on neural-network quantum states that solves the nuclear Schrödinger equation in a systematically improvable fashion, with polynomial scaling in the number of nucleons. This method enables quantum Monte Carlo calculations of medium-mass nuclei, allowing us to study the essential elements of nuclear binding, e. g. the simplest nuclear Hamiltonian capable of describing binding energies and charge radii across the nuclear chart with few-percent accuracy. I will then present applications to condensed-matter systems, such as the ultra-cold Fermi gases in the unitary limit. Perspectives on accessing electroweak responses and the real-time dynamics of quantum many-body systems will also be discussed.
Selected Advances in (Nuclear) Quantum Continuum Physics: Ab Initio Methods and Emulators
Xilin Zhang · Tuesday, August 18 / plenary
Xilin Zhang · Tuesday, August 18 / plenary
The nuclear continuum theory underpins our understanding of critical reaction dynamics in both laboratory experiments and astrophysical environments, while also sharing deep theoretical ties with broader quantum systems. Rather than an exhaustive review, this talk presents a focused perspective on recent methodological developments designed to advance computations in this domain. I will first introduce two recent ab initio frameworks [Phys. Rev. Lett. 125, 112503 (2020); Phys. Rev. Lett. 135, 242501 (2025)] that lay the conceptual groundwork for extending reaction calculations across the nuclear chart, offering fresh strategies for the broader physics community. Next, I will discuss the development of fast and accurate emulators [Phys. Lett. B 809, 135719 (2020); arXiv: 2511.01844] that dramatically reduce computational costs for demanding tasks like model calibration and uncertainty quantification in scattering calculations. The presentation will conclude by briefly exploring how integrating these advances with neural network quantum states [Phys. Rev. Lett. 136, 032501 (2026)] can further push the frontiers of quantum continuum calculations.
Perturbative calculations of light nuclei in χEFT up to N3LO
Oliver Thim · Tuesday, August 18 / Session I.1
Oliver Thim · Tuesday, August 18 / Session I.1
In a recent study 1, we predict ground-state energies of 3 H, 4 He, and 6 Li in chiral effective field theory up to next-to-next-to-next-to-leading-order (N3 LO) using a power counting guided by renormalization-group invariance. Subleading two-nucleon interactions are treated perturbatively, and for 4 He and 6 Li, we calculate the perturbative corrections from numerical derivatives of ground-state energies obtained with Lanczos diagonalization. We find that including the 3 H binding energy in the calibration is essential for robust predictions of 4 He and 6 Li. This work demonstrates that the employed power counting can be applied to construct nuclear interactions with predictive power for light nuclei. In this talk, I will present these results and discuss possible strategies going forward. 1 O. Thim, A. Ekström, and C. Forssén, arXiv:2604.14985 (2026)
Studies in subleading three-nucleon interaction terms
Luca Girlanda · Tuesday, August 18 / Session I.1
Luca Girlanda · Tuesday, August 18 / Session I.1
The nuclear interaction problem can nowadays be addressed within the systematic framework of effective field theories, rooted in the underlying quantum chromodynamics through its approximate and dynamically broken chiral symmetry. Nevertheless, despite tremendous progress, longstanding discrepancies between theory and experiment persist in the A=3 continuum, most notably the so-called Ay puzzle in p-d scattering, due to the poorly known three-nucleon force. We will review its status and the perspectives to solve it via subleading contrubutions to the three-nucleon force at next-to-next-to-next-to-leading order (N3LO), or via specific off-shell components of the two-nucleon interaction arising at the same order.
Recent progress in A=2,3,4 nuclear processes of astrophysical interest
Laura Marcucci · Tuesday, August 18 / Session I.1
Laura Marcucci · Tuesday, August 18 / Session I.1
In this talk, I will present an update on recent theoretical investigations of weak and radiative capture processes of astrophysical interest in systems with A = 2, 3, and 4. In particular, I will review the study of Ref. [1] on the proton-proton weak fusion, carried out within chiral effective field theory (chEFT) using a wide set of nuclear interaction models. This approach has enabled the application of a Bayesian analysis to provide a robust quantification of the theoretical uncertainties. I will then discuss the work of Ref. [2] on the proton-3He weak capture and the neutron-3He radiative capture, also performed within chEFT and employing a broad range of nuclear interaction models. This study provides the most up-to-date estimates of the proton-3He astrophysical S-factor and of the neutron-3He cross section, both at thermal energies and up to a few MeV. It is worth emphasizing that the studies presented in Refs. [1,2] are specifically aimed at addressing all the recommendations formulated in the recent review article of Ref. [3] for these reactions. Finally, I will present the latest results for proton-deuteron radiative capture obtained within chEFT [4] and compare them with the available experimental data for the astrophysical S-factor and for the angular distributions at various center-of-mass energies. [1] V. Barlucchi, A. Gnech, S. Degl’Innocenti, L.E. Marcucci, arXiv:2603.25465 (2026), submitted to Phys. Rev. C [2] M. Viviani, A. Gnech, L.E. Marcucci, A. Kievsky, L. Girlanda, in preparation [3] B. Acharya et al., Rev. Mod. Phys. 97, 035002 (2025) [4] L.E. Marcucci et al., in preparation
Helium-4 Monopole Form Factor
Vittorio Barlucchi · Tuesday, August 18 / Session I.1
Vittorio Barlucchi · Tuesday, August 18 / Session I.1
We investigate the structure of four-nucleon systems to shed light on the nature of the first excited 02+ state of Helium-4 and to address the discrepancy in theoretical calculations of its inelastic monopole form factor. We perform new calculations using local potentials derived within chiral effective field theory at various orders in the chiral expansion. We employ both the hyperspherical harmonics (HH) expansion and the effective interaction HH method, with the aim of benchmarking these approaches using the same dynamical input. We analyze their respective convergence patterns and present results for the binding energies, the position of the 02+ excited state, and the monopole form factor.
The three-nucleon parameter
Alejandro Kievsky · Tuesday, August 18 / Session I.1
Alejandro Kievsky · Tuesday, August 18 / Session I.1
Studying the s-wave sector of a two-body system, we refer to a shallow state when the system has a bound or a virtual state close to the break-up threshold. In this case a strict correlation appears between the energy of this state and the low energy scattering parameters, the scattering length and the effective range. This correlation constrains dynamically the system producing the appearance of universal behavior; values of many observables are determined by that correlation and not by specific details of the interaction between the constituent of the system. In this context, the nuclear system is of particular interest. In both spin-isospin channels, S, T = 1, 0 and 0, 1, the two-nucleon system is close to the unitary limit, the limit in which the scattering length diverges, showing universal behavior. It is possible to use a two-parameter gaussian potential to represent the universal window: \begin{equation} V_G(\beta_G,R_G,r)=-\frac{\hbar^2}{mR_G^2}\beta_G e^{-(r/R_G)^2} \end{equation} and use the values of the scattering length and effective range to determine the potential parameters. At the unitarity point the following general relations hold for gaussian potentials: re /RG = 1.43522 and βG = 2.684. Moreover, using the deuteron values for the binding energy, Ed = 2.224 MeV, and triplet scattering length, 3 a = 5.419 fm, it is possible to determine the gaussian parameters βG = 3.898, RG = 1.56 fm. The process of varying β maintaining RG constant defines a path to the unitarity point. Accordingly at that point the effective range should be re = 1.43522RG , resulting for the deuteron in that limit re = 2.24 fm. Extending the analysis to the three-body sector and using gaussian potentials, we will define a path from the physical point, defined from the triton binding energy, B(3 H)=8.48 MeV, to the unitary point. The energy at that point, E∗3 , defines the nuclear three-body parameter κ∗ from the relation E∗3 = h̄2 κ2∗ /m. We will show that E∗3 ≈ 2.6 MeV, and this value remains relatively stable using different interactions to describe the three-nucleon system. A similar analysis in the fourbody case yields E∗4 = 13.5 MeV. Using the E∗3 and E∗4 values, it would be possible to determine a nuclear interaction at the unitary point from which the nuclear spectrum at that point can be inferred.
Indirect dissociative recombination of small molecular cations
Roman Čurík · Tuesday, August 18 / Session II.1
Roman Čurík · Tuesday, August 18 / Session II.1
We present a theoretical toolkit to study the dissociative recombination (DR) of diatomic cations. The toolkit is based on the energy-dependent frame transformation approach combined with the multi-channel quantum defect theory. The complex vibrational basis satisfies the outgoing-wave boundary conditions that can be implemented by determining the nuclear Siegert states or by using exterior complex scaling of the nuclear Hamiltonian. Another independent part of the toolkit is a simple two-dimensional (2D) model of the DR process. The model has one electronic and one nuclear degree of freedom and it can be solved to high precision, without making any physically motivated approximations [1,2] (as e.g. Born-Oppenheimer approximation). The model was tailored to study the DR of H2+ in the singlet ungerade channels (indirect process) or it can be extended (our present work) to the singlet gerade channels dominated by the direct mechanism. The 2D model also served as a benchmarking tool for our development of the energy-dependent frame transformation theory [3]. This theoretical toolkit was applied to study the DR process of cold HeH+ cations. The resulting rotationally resolved DR rates, convolved over the beam energy distributions relevant to a recent experiment at the Cryogenic Storage Ring, give good agreement between the experiment and theory [4]. Further applications involve singlet gerade and ungerade states of the hydrogen molecule. References 1 D. Hvizdoš, M. Váňa, K. Houfek, C.H. Greene, T.N. Rescigno, C.W. McCurdy, and R. Čurík, Phys. Rev. A 97, 022704 (2018) 2 R. Čurík, D. Hvizdoš, and C.H. Greene, Phys. Rev. A 98, 062706 (2018) [3] D. Hvizdoš, C.H. Greene, and R. Čurík, Phys. Rev. A 101, 012709 (2020) [4] R. Čurík, D. Hvizdoš, and C.H. Greene, Phys. Rev. Lett. 124, 043401 (2020)
Coulomb and dipolar focusing in laser-assisted two-body and three-body collisions
Ilya Fabrikant · Tuesday, August 18 / Session II.1
Ilya Fabrikant · Tuesday, August 18 / Session II.1
Low-energy collisions involving electrons, positrons, positronium (Ps) and atomic hydrogen can be strongly affected by laser fields of a moderate intensity. The Coulomb focusing effect in collisions between two charged particles is due to wiggling motion of electron in a laser field, and has been shown to strongly affect the processes of bremsstrahlung, radiative recombination in electron collisions with protons [1,2], and dissociative recombination in electron collisions with H_2^+ molecular ions [3]. A similar effect, dubbed dipolar focusing, occurs in the process of Ps formation in collisions of positrons with excited hydrogen atoms since the hydrogen atom in an excited state possesses a dipole moment. We calculate cross sections for these processes using classical and semiclassical methods. In particular we use Kramers’ radiation theory for description of laser-assisted radiative recombination.In addition to a substantial enhancement of the cross sections, the results demonstrate the importance of the exact inclusion of the Coulomb singularity and dynamical chaos in the laser-assisted two-body processes. [1] H. B. Ambalampitiya and I. I. Fabrikant, Phys. Rev. A 99, 063404 (2019). [2] I. I. Fabrikant and H. B. Ambalampitiya,Phys. Rev. A 101,53401 (2020). [3] I. I. Fabrikant, H. B. Ambalampitiya, and I. F. Schneider, Phys. Rev. A 103, 053115 (2021).
Dynamics of Electron-Transfer-Mediated Decay in a Weakly Bound Trimer
Jaroslav Hofierka · Tuesday, August 18 / Session II.1
Jaroslav Hofierka · Tuesday, August 18 / Session II.1
Electron-transfer-mediated decay (ETMD) is a highly efficient mechanism for charge and energy redistribution in weakly bound systems. Its dependence on nuclear motion and molecular geometry, however, is not fully understood. We study the NeKr₂ trimer following core ionization of Ne, combining fully dimensional nuclear dynamics with ETMD decay rate calculations and introducing a new 1/R⁶ asymptotic expression for the decay width [1]. We assess the competition between ETMD, which drives Coulomb explosion, and direct dissociation without ETMD. We quantify ETMD efficiency in asymmetric trimer configurations, where charge transfer occurs along the shorter Ne–Kr distance and energy transfer along the longer one. Agreement with recent multiple-coincidence measurements was found [2]. These findings clarify how nuclear dynamics and geometry control nonlocal decay in weakly bound few-body systems. References: [1] Hofierka et al., J. Chem. Theory Comput. 2025, 21, 12026–12033 [2] Trinter et al., J. Am. Chem. Soc. 2026, 148, 4126–4135
Coupled-channels method for the scattering hypervolume in ultracold atomic three-body collisions
Pim Kersbergen · Tuesday, August 18 / Session II.1
Pim Kersbergen · Tuesday, August 18 / Session II.1
We introduce a novel coupled‑channels method for elastic three‑body scattering in systems of identical bosonic alkali‑metal atoms. The approach relies on the numerically exact two‑body off‑the‑energy‑shell transition matrix, constructed from realistic multichannel molecular interaction potentials that support many bound states. By rigorously accounting for this off‑shell structure, the method captures both the short‑range physics as well as multichannel couplings characteristic of alkali‑metal potentials without resorting to model pseudopotentials. The central output is the complex three‑body scattering hypervolume—the three‑body analogue of the two‑body scattering length—which we obtain with controlled and verifiable numerical accuracy. As a realistic benchmark, we apply our framework to spin‑polarized potassium-39 and lithium-7, performing full coupled‑channels three‑body scattering calculations and extracting the hypervolume over experimentally relevant conditions. The method is general and transferable to other atomic species and interaction models featuring deep molecular potentials with an arbitrarily large number of bound states.
Three-body bound states in a continuum
Lucas Happ · Tuesday, August 18 / Session II.1
Lucas Happ · Tuesday, August 18 / Session II.1
Resonances in quantum few-body systems are inherently unstable, decaying into continuum states of their constituent subsystems with a finite lifetime. In this talk, we present a mechanism by which three-body resonances can be stabilized into so-called bound states in the continuum (BICs), states embedded in the continuum spectrum that nevertheless exhibit vanishing decay width. Using a two-channel framework, we show that the lifetime can be made arbitrarily long through continuous tuning of system parameters. We illustrate the mechanism in two complementary examples: a mass-imbalanced one-dimensional system and a three-dimensional system of identical bosons in the Efimov regime. In the latter case, we demonstrate that a three-body BIC can be reached by tuning an external magnetic field, a standard experimental tool in cold-atom experiments.
Towards Improving the Top-Row CKM Unitarity Test with Precision Beta Decay in Nuclei
Michael Gennari · Tuesday, August 18 / Session III.1
Michael Gennari · Tuesday, August 18 / Session III.1
Recent analysis of Fermi decays by C.Y. Seng and M. Gorshteyn and the corresponding Vud determination have revealed a degree of tension with Cabibbo-Kobayashi-Maskawa (CKM) matrix unitarity, confirmation of which would indicate several potential deficiencies within the Standard Model (SM) weak sector. Extraction of Vud requires electroweak radiative corrections (EWRC) from theory to be applied to experimentally obtained f t-values. Novel calculations of corrections sensitive to hadronic structure, i.e., the γW -box, are at the heart of the recent tension. Moreover, to further improve on the extraction of Vud , a modern and consistent treatment of the two nuclear structure dependent corrections is critical. These corrections are (i) δC , the isospin symmetry breaking correction (ii) and δN S , the EWRC representing evaluation of the γW -box on a nucleus. Preliminary estimations of δNS have been made in the aforementioned analysis, however, a true nuclear many-body theory calculation of the quantity is required for desired precision goals. Via collaboration with C.Y. Seng and M. Gorshteyn and use of the Lanczos strengths method, these corrections can be computed in ab initio nuclear theory for the first time. We apply the no-core shell model (NCSM), a nonrelativistic quantum many-body theory for describing low-lying bound states of s- and p-shell nuclei starting solely from nuclear interactions. We will present preliminary results for δNS and δC as determined in the NCSM for the 10 C → 10 B and 14 O → 14 N beta transitions, with the eventual goal of extending the calculations to 18 Ne → 18 F and other light transitions.
The leading nuclear-structure electrostatic correction in arbitrary beta transitions
Daniel Benatar · Tuesday, August 18 / Session III.1
Daniel Benatar · Tuesday, August 18 / Session III.1
We develop a systematic theoretical framework to improve theoretical predictions for nuclear β decays of arbitrary angular momentum J by incorporating nuclear corrections to the Coulomb interaction between the emitted lepton and the nuclear charge distribution, useful for ongoing and future precision searches for Beyond-the-Standard-Model (BSM) physics. As such, we emphasize the dominant sources of theoretical uncertainty and estimate their size. The formalism is based on nuclear matrix elements expanded in multipole operators, as commonly used in \emph{ab initio} calculations. First-order Coulomb corrections are derived from one-photon exchange, and subsequently expanded in the relevant small parameters of the nuclear problem. We additionally provide explicit results for allowed Gamow–Teller and unique first-forbidden transitions.
First model calculation of the γ-spectrum from d–³He collisions around 3/2⁺ resonance
Natalia Timofeyuk · Tuesday, August 18 / Session III.1
Natalia Timofeyuk · Tuesday, August 18 / Session III.1
Recently, motivated by possible industrial fusion applications of the γ-rays accompanying d-t collisions, the first model calculations of the minor branching ratio of the d + t → α + n + γ reaction, have been published [1]. This model exploited the most relevant physics feature – spin conservation in electric dipole transitions – which resulted in a peculiar mechanism of this reaction: γ-emission via bremsstrahlung from an intermediate α − n state. Because of the bremsstrahlung, the γ-spectrum was found to contain non-zero contributions at all energies thus making inclusive dt-γ cross section measurements sensitive to the low-energy cutoff of the detected gammaevents. Comparison of the model predictions to existing measurements in accelerators, inertial confinement fusion facilities and Joint European Torus suggests a possible contradiction between results from these experiments. Dedicated studies of the γ-spectrum from the mirror reaction d+3 He→ α + p + γ could potentially help resolving this contradiction. In this talk I present the first model spectrum calculations for the branching of the d+3 He→ α + p + γ reaction around the 3/2+ resonance which is governed by the same reaction mechanism as the dt-γ at the energies corresponding to typical plasma environments. Comparison to an existing d3 He-γ accelerator measurement is presented and its connection to the mirror dt-γ reaction is discussed. [1] N.K. Timofeyuk, G.W. Bailey and M.R. Gilbert, Phys. Rev. C 110, 014612 (2024) UK Ministry of Defence © Crown Owned Copyright 2026/AWE.
Compton Scattering Studies on ³He and ⁴He at HIGS
Gerald Feldman · Tuesday, August 18 / Session III.1
Gerald Feldman · Tuesday, August 18 / Session III.1
The High Intensity Gamma-Ray Source (HIGS) at Duke University delivers monoenergetic photon beams with high linear or circular polarization by backscattering of free-electron laser (FEL) photons [1]. To exploit the unique capabilities of this facility, we have been performing a series of Compton scattering experiments on light nuclei aimed at determining the nucleon electromagnetic polarizabilities. We have cryogenic liquid 1 H, 2 H, and 4 He targets, and a recent upgrade enables us to liquefy 3 He as well. To measure the scattered photons, we utilize two of the world’s largest NaI detectors – BUNI (from Boston University) and DIANA (from University of Kentucky) – each having better than 2% photon energy resolution. We are also using an array of eight medium-sized NaI detectors to enhance our angular coverage and to serve as out-of-plane detectors for polarized photon measurements. Thus far, our completed experiments consist of 2 H [2] and 4 He [3] below 85 MeV with unpolarized photons, as well as 1 H with polarized photons [4], providing high precision data for comparison with chiral Effective Field Theory calculations [5] which will be used to extract the EM polarizabilities of the neutron (αn and βn ). Now we have extended our unpolarized measurements to 3 He at a higher energy (100 MeV) [6], which can be compared to a relatively new theoretical development for the A = 3 system [7]. We have also performed a lower-energy experiment on 3 He at 60 MeV [8] to serve as a benchmark for the theory. These recent measurements constitute the first Compton data ever taken on a 3 He target. The rationale for 3 He is to provide an alternate means of accessing αn and βn in an entrance channel independent of the usual deuteron experiments and with a different linear combination of proton and neutron contributions. Going farther, we have also extended our measurements to higher energies for 4 He (100 and 87 MeV) [9] in order to exploit a very recent theoretical approach [10] for handling few-nucleon systems with A > 3. The principal advantages of this particular experiment are the lack of excited states or breakup channels below 19.8 MeV (hence the elastic Compton peak is very clean) and the higher cross section for A = 4 (enabling high statistics). With this new theoretical framework now available (see next talk by H. Griesshammer for more details), we have just been approved to run a new experiment at HIGS on 6 Li in the summer, a case for which the theoretical treatment is still applicable. Overall, our Compton scattering program at HIGS is fairly broad, and this talk will provide an overview of the recent experimental activities on 3 He and 4 He. The results of our recent work will be reviewed, preliminary results of our ongoing measurements will be shown, and prospects for future experiments and their impact will be discussed. [1] H.R. Weller et al., Prog. Part. Nucl. Phys. 62, 257 (2009). [2] D. Godagama et al., submitted to Phys. Rev. C (2026). [3] X. Li et al., Phys. Rev. C101, 034618 (2020); M. Sikora et al., Phys. Rev. C96, 055209 (2017). [4] X. Li et al., Phys. Rev. Lett. 128, 132502 (2022). [5] H.W. Griesshammer et al., Prog. Part. Nucl. Phys. 67, 841 (2012). [6] J. Zhou, Ph.D. thesis, Duke University (2026). [7] A. Margaryan et al., Eur. Phys. J. A54, 125 (2018). [8] E. Mancil, Ph.D. thesis, Duke University (2026). [9] M. Lewis, APS Bulletin, 92nd Annual Southeastern Section (SESAPS) Meeting (2025). [10] H.W. Griesshammer et al., Eur. Phys. J. A60, 132 (2024).
Scattering Photons and Other Particles from Nuclei Up To ⁶Li and Beyond
Harald W. Grießhammer · Tuesday, August 18 / Session III.1
Harald W. Grießhammer · Tuesday, August 18 / Session III.1
Scattering probes the symmetries and strengths of nucleonic and nuclear interactions and relates them to lattice-QCD computations of fundamental hadronic properties. In Compton scattering, the nucleon polarisabilities parametrise the stiffness of charge and spin distributions against deformations, important for example for the proton-neutron mass difference and for the nucleonic Faraday effect. Concurrently, it tests the charged pion-exchange contribution to nuclear binding. I first review the theory side of the synergistic international effort of experimentalists and theorists in Compton scattering on few-nucleon systems. The first-ever computations for 4 He and 6 Li rely on the Transition Density Amplitude formalism, an efficient way to calculate interactions of probes with light nuclei, especially when supplemented with “SRG-And-Back”, a new implementation of the Similarity Renormalisation Group. It exploits factorisation between nuclear structure and interaction kernels at momenta ∼ mπ and is markedly more computationally efficient, taking full advantage of the numerical power of modern few-nucleon methods. One- and two-body transition densities that encode the nuclear structure of the target at a given momentum transfer are evaluated once and stored, and then convoluted with different interaction kernels to produce observables. Conversely, for different nuclei, the same kernels can be used. After summarising method, status and prospects, I present results for Compton scattering, pion photoproduction and pion scattering on 3 He, 3 H, 4 He and 6 Li in Chiral Effective Field Theory and compare to available data. Coordinated with G. Feldman’s contribution on Compton scattering experiments. Work in collaboration with A. P. Long (GW), J. A. McGovern (U. of Manchester), A. Nogga and X.X. Sun (FZ Jülich) and D. R. Phillips (Ohio U.). Supported in part by US DoE award DE-SC0015393.
Effective field theory for three- and four-boson systems near the unitarity limit
Feng Wu · Tuesday, August 18 / Session I.2
Feng Wu · Tuesday, August 18 / Session I.2
The three- and four-boson systems near the unitarity limit exhibit universal behavior described by Short-Range Effective Field Theory. At leading order, the unitary limit gives rise to discrete scale invariance and the Efimov effect, governed by a single three-body scale. For general separable regulators, it is shown that the three-body limit cycle follows from a real Möbius transformation characterized by three parameters. Deviations from unitarity, including corrections from finite scattering length and effective range, as well as a four-body force required by renormalization, can be incorporated systematically in perturbation theory. Using Faddeev–Yakubovsky and diagrammatic methods, we obtain well-converged predictions for binding energies and radii. Our results for 4 He clusters show good agreement with those obtained from sophisticated phenomenological potentials, indicating that the physics of 4 He clusters is governed by only small deviations from discrete scale invariance.
Towards an EFT Description of Alpha Clustering in Nuclei
Matúš Rojík · Tuesday, August 18 / Session I.2
Matúš Rojík · Tuesday, August 18 / Session I.2
In this work, we investigate cluster effective field theory (EFT) with alpha particles treated as elementary degrees of freedom. While halo EFT has been successfully used to describe systems consisting of a core and a few valence nucleons, an EFT tailored to nuclear clustering phenomena remains largely unexplored. We discuss the necessary modifications to contact EFTs to account for the near-threshold 8 Be resonance. Two low-energy constants are required at leading order, fitted to alpha–alpha scattering phase shifts. This framework enables a description of the first 0+ excited state of 12 C (the Hoyle state) as a three-alpha resonance, as well as the near-threshold 0+ excited state of 16 O. Our approach provides a computationally tractable framework for describing alpha-clustered states in heavier nuclei and offers a promising route toward astrophysically relevant reactions such as 12 C(α,γ)16 O, which remain challenging for state-of-the-art ab initio methods.
Inferring breakdown scales in baryon chiral perturbation theory
Matthias Schindler · Tuesday, August 18 / Session I.2
Matthias Schindler · Tuesday, August 18 / Session I.2
In baryon chiral perturbation theory (BChPT), static properties of the nucleon, such as its mass mN and axial-vector coupling gA , are determined order-by-order in an expansion in the ratio of the pion mass to a breakdown scale ΛB . We apply Bayesian methods to infer the breakdown scales for these two observables and find notably different results. While our pointwise analysis gives a ΛB of approximately 500 MeV in the case of the nucleon mass, the breakdown scale for the axial-vector coupling gA is significantly smaller.
Nd-scattering from 3N-induced forces SRG transformation
Vaibhav Chahar · Tuesday, August 18 / Session I.2
Vaibhav Chahar · Tuesday, August 18 / Session I.2
We investigate nucleon–deuteron (Nd) scattering in the presence of three-nucleon (3N) interaction effects induced by the Similarity Renormalization Group (SRG) transformation. While SRG evolution is widely used to soften nuclear Hamiltonians and improve convergence in few- and many-body calculations, it also generates many-body forces even when the initial interaction contains only two-body terms. In this work, we focus on the role of SRG-induced 3N forces in Nd scattering observables and analyze how their inclusion affects the consistency and scale dependence of the results. By comparing calculations with and without induced three-body contributions, we assess their impact on elastic scattering observables and explore the extent to which they restore unitarity and reduce dependence on the SRG flow parameter. Our study provides insight into the interplay between renormalization methods and few-body dynamics, and highlights the importance of induced many-body interactions for a reliable description of low-energy nuclear reactions.
Bound states in the continuum in cuprous oxide quantum wells
Pavel Belov · Tuesday, August 18 / Session II.2
Pavel Belov · Tuesday, August 18 / Session II.2
Bound states in the continuum (BICs) [1] are remarkable quantum states characterized by the absence of linewidth broadenings, and therefore exhibiting giant nonradiative lifetimes. The existence of bound states embedded in the continuum was first suggested by von Neumann and Wigner in the context of an open quantum system formed by a rapidly oscillating potential [2]. One century later, BICs became of practical relevance in photonics as particular solutions of the wave equation [3,4]. They are the subject of extensive study in quantum optics due to their unique properties, including the ability to enhance light-matter interactions, produce sharp Fano resonances and generate extremely long-lived and confined single-photon excitations [5]. However, the proposed quantum-mechanical systems incorporating BICs still fall into the category of speculative theoretical work, rather than practical realization. The theoretical setups [2,6] designed so far are difficult to implement in atomic systems as they require rather challenging circumstances. In this report, we propose a realistic semiconductor system containing BICs which allows for a practical realization [7]. By varying the confinement strength of excitons in cuprous oxide quantum wells [8], we demonstrate the appearance of long-lived Rydberg states of confined electronhole pairs in a continuum background. The trivial symmetry-protected BICs in this system are formed due to the different parities of the charge-carrier subbands, while the proper nontrivial BICs appear as a result of the Friedrich-Wintgen destructive interference between adjacent exciton resonances [6]. Calculations of the linewidths based on the quantum defect theory [9] applied to the coupled-channel Schrödinger equation with three channels are confirmed by a numerically exact solution using a B-spline basis and the complex-coordinate-rotation method [10,11]. We argue that finite-sized cuprous oxide crystals, due to their large exciton binding energies, are a convenient platform for experimental identification of BICs. [1] C. W. Hsu et al., Nat. Rev. Mat. 1, 16048 (2016). [2] J. von Neumann and E. Wigner, Phys. Z. 30, 465 and 467 (1929). [3] D. C. Marinica et al., Phys. Rev. Lett. 100, 183902 (2008). [4] Y. Plotnik et al., Phys. Rev. Lett. 107, 183901 (2011). [5] G. Calajó et al., Phys. Rev. Lett. 122, 073601 (2019). [6] H. Friedrich and D. Wintgen, Phys. Rev. A 32, 3231 (1985). [7] A. Aslanidis et al., Phys. Rev. B 111, L121103 (2025). [8] P. A. Belov et al., Phys. Rev. B 109, 235404 (2024). [9] M. J. Seaton, Rep. Prog. Phys. 46, 167 (1983). [10] N. Moiseyev, Phys. Rep. 302, 212 (1998). [11] N. Scheuler et al., Phys. Rev. B 109, 165440 (2024).
Two- and Three-body interactions in the stability of Exciton-polariton condensates
Lauro Tomio · Tuesday, August 18 / Session II.2
Lauro Tomio · Tuesday, August 18 / Session II.2
In an extension of the usual Gross-Pitaevskii approach with nonlinear two-body contact interaction, we study the role of three-body nonlinear interactions with a spatially dependent pumping profile for the stability of polariton Bose–Einstein condensates (PBECs). By considering weak and strapless confinements, we show that the combined actions of linear and nonlinear loss and gain terms can dynamically stabilize the condensate against collapse or unbounded expansion. The analytical stability predictions obtained from the variational approach are validated through direct numerical simulations.
Exploring Collectivity in Few-Body Systems with Density Functional Theory
Uri Sharell · Tuesday, August 18 / Session II.2
Uri Sharell · Tuesday, August 18 / Session II.2
Recent experiments with ultracold fermionic gases have demonstrated that even in extremely small systems with only 10 atoms, fluid-like behaviour can emerge 1. As this is far outside the traditional regime of applicability for hydrodynamics, this ongoing project seeks to understand how this can arise from the microscopic interactions. We briefly review density functional theory (DFT) and explain how it can be used to bridge few- to many-body physics for both stationary and dynamic computations. We then motivate a specific functional to describe strongly interacting Fermi systems, the superfluid local density approximation (SLDA) 2, which we have used to model the initial profile and subsequent dynamics of 10 strongly interacting fermionic atoms confined in two dimensions by an optical trap. We present some of our recent results showing remarkable agreement with the experimental data for the initial density profile of such a system. We further show that the time-dependent DFT computation qualitatively reproduces interaction-driven elliptic flow, providing a preliminary theoretical account of emergent collective behaviour in this few-body system. References 1 S. Brandstetter et al., “Emergent interaction-driven elliptic flow of few fermionic atoms,”Nat. Phys., vol. 21, no. 1, pp. 52–56, Jan. 2025, doi: 10.1038/s41567-024-02705-8. 2 G. Wlazłowski, P. Magierski, M. M. Forbes, and A. Bulgac, “W-SLDA Toolkit: A simulation platform for ultracold Fermi gases,”Feb. 09, 2026, arXiv: arXiv:2602.08982. doi: 10.48550/arXiv.2602.08982
Emergence of collectivity in few-body system — Fluid dynamics perspective
Toshali Mitra · Tuesday, August 18 / Session II.2
Toshali Mitra · Tuesday, August 18 / Session II.2
Recent experiments demonstrating collective behavior through interaction-driven anisotropic expansion of ten fermions released from an elliptic trap raise a key question: how does collectivity emerge in quantum systems with only a few degrees of freedom? While hydrodynamics successfully describes strongly interacting many-body systems, its applicability to few-fermion systems remains uncertain. In this ongoing work, we explore whether such behavior can be captured within a viscous hydrodynamic framework by adapting simulations—originally developed for large cold atom systems —to regimes with very small particle numbers. This study aims to probe the limits of hydrodynamic descriptions and identify the minimal requirements for collectivity in strongly interacting fermionic systems.
Entanglement suppression for ΩΩ scattering
Tetsuo Hyodo · Tuesday, August 18 / Session III.2
Tetsuo Hyodo · Tuesday, August 18 / Session III.2
We study entanglement suppression in s-wave ΩΩ scattering, where each baryon has spin 3/2. By treating the S-matrix as a quantum operator acting on the spin states, we quantify its ability to generate entanglement and identify the conditions on the phase shifts of the spin channels that minimize entanglement generation in the system. In ΩΩ scattering, only antisymmetric spin channels are allowed due to Fermi-Dirac statistics. Applying the entanglement-suppression framework to ΩΩ scattering, we find two solutions for the phase shifts: one leading to a spin SU(4) symmetry and the other to a nonrelativistic conformal symmetry. We show that the solution associated with the nonrelativistic conformal symmetry originates from the specific structure of the ClebschGordan coefficients in the 3/2 ⊗ 3/2 system. [1] T.-R. Hu, K. Sone, F.-K. Guo, T. Hyodo and I. Low, Phys. Rev. Res. 7, 043306 (2025). [2] K. Sone, T.-R. Hu, F.-K. Guo, T. Hyodo and I. Low, arXiv:2602.09630 [hep-ph].
Di-J/ψ scattering states with the quark Pauli-blocking effect
Sachiko Takeuchi · Tuesday, August 18 / Session III.2
Sachiko Takeuchi · Tuesday, August 18 / Session III.2
The LHCb, ATLAS, and CMS collaborations have reported peaks in the final J/ψ-J/ψ invariant mass spectra [1-3]. The peaks are reported to be 2++ [4]. We investigated scattering states of two heavy mesons, such as J/ψ-J/ψ, ηc -J/ψ, ηc -ηc , Υ-Υ, etc., using a simplified quark-cluster model. It is found that the Pauli exclusion effect on the quarks or the antiquarks (which we call the quark Pauli-blocking effect) causes a rapid increase and a node in the two-meson phase shifts of total spin J=1 and 2. The increase is not large enough to be regarded as a usual resonance, but the scattering matrix has a corresponding pole. The node and the pole are observed in the Lattice QCD calculation [5], but not in the four-quark complex scaling model calculation [6]. This work supports the Lattice QCD result, and our result indicates that the origin of the zero point of the scattering phase shift comes from the quark Pauli-blocking effect. We conclude that the quark Pauli-blocking effect causes a structure in the spectra. It should be considered to investigate heavy quark systems. A part of this work has been published in Sachiko Takeuchi, Atsushi Hosaka, Makoto Takizawa, and Yasuhiro Yamaguchi, PoS, QCHSC24:119, 2025, and PoS, HADRON2025:073, 2026. [1] Roel Aaij et al. Observation of structure in the J/ψ-pair mass spectrum. Sci. Bull., 65(23):1983– 1993, 2020. [2] Georges Aad et al. Observation of an Excess of Dicharmonium Events in the Four-Muon Final State with the ATLAS Detector. Phys. Rev. Lett., 131(15):151902, 2023. [3] Aram Hayrapetyan et al. New Structures in the J/ψJ/ψ Mass Spectrum in Proton-Proton √ Collisions at s=13 TeV. Phys. Rev. Lett., 132(11):111901, 2024. [4] Aram Hayrapetyan et al. Determination of the spin and parity of all-charm tetraquarks. Nature, 648(8092):58–63, 2025. [5] Geng Li, Chunjiang Shi, Ying Chen, and Wei Sun. Tensor Resonance in J/ψJ/ψ Scattering from Lattice QCD, arXiv:2505.24213[hep-lat], 2025. [6] Guang-Juan Wang, Qi Meng, and Makoto Oka. S-wave fully charmed tetraquark resonant states. Phys. Rev. D, 106(9):096005, 2022.
First experimental study of axial-vector meson–nucleon interactions using p-f1 correlations with ALICE
Laura Šerkšnytė · Tuesday, August 18 / Session III.2
Laura Šerkšnytė · Tuesday, August 18 / Session III.2
Chiral symmetry in QCD is expected to be partially restored at high temperature and/or baryon density, where the chiral condensate that generates most hadron masses decreases. A key manifestation of this restoration is the degeneracy in mass of chiral partners, such as vector and axialvector mesons. To identify these effects, it is essential to achieve a precise understanding of the interaction between vector mesons and nucleons, which plays a crucial role in their in-medium modifications. However, this has long been inaccessible to experiments due to the short lifetimes of these mesons. ALICE has demonstrated that such residual strong interactions can be probed via femtoscopy through two-particle relative-momentum correlations. In this contribution, the first experimental study of strong interaction effects in the axial-vector meson sector is presented, via the p-f1 correlation function measured in pp collisions by ALICE and enabled by the large data samples collected during LHC Run 3. The p-f1 measurement is compared to FCA calculations, which treat f1 as a K ∗ K̄ − K̄ ∗ K molecule. Together with p-ρ results, these results provide new constraints on nucleon-(axial-)vector meson interactions and their connection to chiral dynamics.
Exclusive charmonium production in e⁻e⁺ annihilation: ISR and Two-Photon Processes in a Bethe–Salpeter equation framework
Shashank Bhatnagar · Tuesday, August 18 / Session III.2
Shashank Bhatnagar · Tuesday, August 18 / Session III.2
We present a unified study of exclusive charmonium production in electron–positron annihilation within a relativistic Bethe–Salpeter framework, focusing on two complementary mechanisms relevant to few-body dynamics. First, we investigate the initial state radiation (ISR) process e− e+ → γ + J/Ψ [1], followed by the leptonic decay, J/Ψ → µ− µ+ at B-factory energies. The production amplitude is evaluated incorporating the bound-state structure of the J/Ψ, and the resulting cross sections are compared with available experimental measurements, showing reasonable agreement. Second, we study twophoton mediated exclusive double charmonium production processes [2-3], e− e+ → γ ∗ γ ∗ → χc1 + ηc and e− e+ → γ ∗ γ ∗ → hc + hc . Particular emphasis is placed on the role of relativistic bound-state effects and the sensitivity of the cross sections to the internal momentum structure of the meson wavefunctions. We find that the double P-wave channel exhibits a pronounced dependence on the confinement scale parameter entering the Bethe–Salpeter kernel, reflecting the importance of higher-momentum components in the production amplitude. Our results demonstrate that such processes provide sensitive probes of the interplay between relativistic few-body dynamics and non-perturbative QCD effects in heavy quarkonium systems. References: [1] S.Bhatnagar, PRD112, 054011 (2025). [2] A. Okram, S.Bhatnagar (Communicated 2026). [3] S.Bhatnagar, H.Negash, Nucl. Phys. A1053,122969 (2025).
Three-Baryon Femtoscopy as an Effective 3→3 Scattering Experiment (FBS Award)
Laura Šerkšnytė · Wednesday, August 19 / plenary
Laura Šerkšnytė · Wednesday, August 19 / plenary
A major open challenge in hadron physics is the experimental access to three-body dynamics, particularly in systems of unbound hadrons where conventional scattering techniques remain out of reach. This talk presents the development and implementation of a three-body femtoscopy framework that enables the measurements of three-particle correlation functions to study the residual strong interaction between hadrons. √ The three-proton correlation function measured in pp collisions at s = 13.6 TeV at the Large Hadron Collider is presented as a benchmark of the method. A newly developed analysis strategy isolates the genuine correlation and allows direct comparison with state-of-the-art continuum three-body calculations. This measurement provides the first experimental access to the isospin T = 3/2 three-nucleon system and demonstrates sensitivity to the partial-wave structure of the nucleon–nucleon interaction. The convergence of the three-body wave function expansion requires inclusion of the nuclear interaction up to high grand-angular momentum K ≤ 7, revealing for the first time the experimental signature of an effective long-range attraction in a three-proton continuum system. These results establish three-hadron femtoscopy as an effective 3 → 3 scattering framework with three unbound hadrons in both initial and final states. The copious production of hadrons at the LHC, including those carrying strangeness, allows extending this method beyond the nucleonic sector. The p–p–Λ correlation function is also presented, with comparison to the first theoretical predictions, demonstrating sensitivity to three-body interactions.
A study of bound state and resonance phenomena in atomic and nuclear few-body systems (FBS Award)
Michael Higgins · Wednesday, August 19 / plenary
Michael Higgins · Wednesday, August 19 / plenary
We present previous work in atomic and nuclear physics, with a focus on five-body recombination of identical bosons and on bound and resonant states in helium isotopes within the framework of the adiabatic hyperspherical representation. We review studies of the few-body helium systems 4 He+2n, 4 He+3n, and 4 He+4n, where calculations are performed to characterize bound states, resonances, and continuum scattering states, such as computing elastic collision and recombination rates. Comparisons are made between results obtained using the adiabatic hyperspherical approach and those from alternative techniques commonly employed in nuclear physics. We then discuss the quantification of the five-body recombination rate coefficient for five interacting identical bosons, using the WKBJ formalism applied to the lowest five-body hyperspherical adiabatic potential curve. These results are compared with the sole existing experimental measurement of five-body loss in an ultracold gas of bosonic cesium atoms, as well as with the only available theoretical estimate. Finally, the recombination rate for the process B+B+B+B+B→B4 +B is computed in a regime of scattering lengths that supports a single four-body bound state. In the latter half of this talk, we present recent results from a study of dipolar molecules in static electric fields. Recent progress in establishing collisional shielding between dipolar molecules has stimulated significant experimental and theoretical advances, owing to the enhanced stability of these systems against chemical reactions. In our current theoretical work, we investigate the bound-state and scattering properties of dipolar few-body systems in the presence of a static electric field. Our model explicitly includes the molecular rotational structure and long-range dipole– dipole interactions. The primary goal of this research is to develop a deeper understanding of field-induced molecular mixing and its impact on molecule–molecule collisions, as well as on the formation of long-range dipolar dimer states—namely, bound states and resonances composed of two or more dipolar molecules.
Measurement of radiative emission in the d + t → α + n + γ fusion reaction
Andrea Dal Molin · Wednesday, August 19 / plenary
Andrea Dal Molin · Wednesday, August 19 / plenary
Fusion plasmas provide a unique environment where few-body nuclear physics and many-body plasma physics naturally intersect, offering opportunities for progress in both fields. In this context, plasma physics can directly benefit from advances in few-body nuclear physics. Accurate measurement of fusion yield is a key parameter for evaluating the performance of confined plasmas. Traditionally, all direct fusion yield measurements in magnetic confinement reactors rely on a single technique: absolute neutron counting. This presents a challenge in the fusion field, as experimental results cannot be independently cross-validated. By leveraging the few-body description of the rare radiative branch of the deuterium-tritium reaction, recent experiments at the Joint European Torus (JET) have established gamma-ray spectroscopy as a promising, neuronindependent diagnostic for the direct cross-validation of fusion yields [1, 2, 3]. Conversely, fusion plasmas offer new opportunities for studying nuclear physics. Extracting quantitative information from gamma-ray spectra requires accurate nuclear models and cross sections, which are traditionally validated against accelerator experiments. Fusion plasmas provide a unique and complementary environment for testing these models, enabling measurements with reduced background that are difficult to achieve in conventional accelerators. In this contribution, we present results from JET deuterium-tritium campaigns, describe the nuclear models considered in our analysis, and discuss extensions to aneutronic reactions such as D-³He and p-¹¹B, where gamma-ray diagnostics are particularly well suited. [1] A. Dal Molin, G. Marcer, M. Nocente, M. Rebai, D. Rigamonti et al. (2024). Measurement of the Gamma-Ray-to-Neutron Branching Ratio for the Deuterium-Tritium Reaction in Magnetic Confinement Fusion Plasmas. In Physical Review Letters (Vol. 133, Issue 5). American Physical Society (APS). [2] M. Rebai, D. Rigamonti, A. Dal Molin, G. Marcer et al. (2024). First direct measurement of the spectrum emitted by the 3H (2H, ) 5He reaction and assessment of the relative yield 1 to 0. In Physical Review C (Vol. 110, Issue 1). American Physical Society (APS). [3] G. Marcer et al. (2025). Absolute measurement of the deuterium–tritium reaction gamma-ray emission in magnetic confinement fusion plasmas. In Nuclear. Fusion 65 086036.
Chiral Symmetry Preserving Nuclear Forces
Hermann Krebs · Wednesday, August 19 / plenary
Hermann Krebs · Wednesday, August 19 / plenary
Chiral effective field theory is a well-known tool for the description of nuclear physics in the lowenergy sector. Far below the pion production threshold, one can use the Goldstone-boson nature of the exchanged pions to obtain the most general expansion of the nuclear forces in powers of low momenta, divided by a breakdown scale of the theory of order 600 MeV. In the last three decades, chiral two- and three-nucleon forces have been worked out to very high order. In my talk, I will review recent applications of these forces to the description of nuclear structure within LENPIC (Low Energy Nuclear Physics International Collaboration). I will also give an update on the construction of the three-nucleon forces up to next-to-next-to-next-to-leading order (N3LO) in chiral expansion, and will show how to construct them in a way that preserves chiral symmetry.
Effective field theory on the lattice
Dean Lee · Wednesday, August 19 / plenary
Dean Lee · Wednesday, August 19 / plenary
I review recent progress in studies of nuclear many-body systems using nuclear lattice effective field theory. Some of the topics include calculations of nuclear clustering, multimodal superfluidity, and new computational approaches.
Bound States and Resonances in a Box (and beyond)
Sebastian König · Wednesday, August 19 / plenary
Sebastian König · Wednesday, August 19 / plenary
Simulating quantum systems in a finite volume is a powerful theoretical tool for extracting information about them. The observation that the real-world properties of states are encoded in how their discrete energy levels change with the size of the volume gives rise to a versatile formalism that is relevant not only for nuclear physics, but also for other fields such as simulations of cold atomic systems. This talk gives an overview of recent progress that has been achieved in the field of finite-volume few-body physics, covering in particular systems of charged particles and resonance states. Characterized by being strongly coupled to the continuum, resonances are notoriously challenging to describe theoretically and to compute numerically, especially when they appear as genuine fewbody phenomena. As this talk will show, finite periodic boxes allow for an elegant implementation of the non-Hermitian quantum mechanical framework that gives direct access to the properties of few-body resonance states, leading to various applications and inspirations for other techniques.
Few-body femtoscopy by STAR
Ashutosh Pandey · Thursday, August 20 / plenary
Ashutosh Pandey · Thursday, August 20 / plenary
Femtoscopic techniques provide a direct tool to measure the space–time extent and dynamical evolution of the system created in heavy-ion collisions. Identical pion pairs have conventionally been used for source size measurements because of their large production yields and well-understood interactions. In addition to determining the source dimensions, femtoscopic analyses offer a powerful approach to investigate the final-state interactions among different particle species, including both strong and Coulomb interactions. In this talk, we will present a review of recent femtoscopic measurements performed by the STAR experiment at RHIC. The review will cover recent results on pion, kaon, proton, strange-baryon, and light-nuclei femtoscopy. The results include correlations of both identical and non-identical pairs of mesons and baryons, which arise from quantum statistics and final-state interactions and provide unique information on the space–time characteristics of particle production. Particular emphasis will be given to recent measurements from the Beam Energy Scan-II (BES-II) program, including both fixed-target and collider-mode operations, as well as from Au+Au and isobar (Ru+Ru √ and Zr+Zr) collisions at sN N = 200 GeV.
Can the strong interactions between hadrons be determined using femtoscopy?
Evgeny Epelbaum · Thursday, August 20 / plenary
Evgeny Epelbaum · Thursday, August 20 / plenary
Femtoscopic measurements from heavy-ion collisions have become a popular tool to investigate the strong interactions between hadrons. Analysis of femtoscopy data relies on the Koonin-Pratt formula, which relates the measured correlation functions with the relative wave function of an outgoing hadron pair and a source term that is assumed to be universal across interaction models. I will critically assess this universality assumption and show that the interpretation of femtoscopic measurements suffers from a potentially large intrinsic uncertainty due to the inherent scheme dependence of hadronic interactions. I will also comment on the ongoing efforts to explore threebody interactions using this experimental technique.
Few-body nuclear systems with an antikaon
Tadashi Hashimoto · Thursday, August 20 / plenary
Tadashi Hashimoto · Thursday, August 20 / plenary
Kaonic nuclear bound states are exotic few-body systems in which an antikaon acts as a constituent particle. They offer a unique testing ground for the strongly attractive K̄N interaction below threshold and for the interplay between mesonic and baryonic degrees of freedom in compact nuclear systems. The simplest candidate, “K − pp”, was observed at J-PARC E15 in the Λp invariant-mass spectrum of the in-flight K − reaction on helium-3, demonstrating the importance of complete kinematic reconstruction with a large-acceptance solenoid spectrometer. We are now extending this approach to a systematic few-body program with an upgraded solenoidbased spectrometer. The forthcoming E80 experiment at J-PARC will investigate the three-nucleon kaonic system “K − ppn” using a helium-4 target, via decay channels such as Λd, Λpn, and πΣd, to clarify its binding mechanism and internal structure. In addition, E89 will determine the spinparity of “K − pp” through spin-correlation measurements of Λp and search for the isospin partner “K̄ 0 nn”. These studies will establish kaonic nuclei as a new class of strange few-body systems. In this contribution, we will review our achievements in the past decade and discuss the future perspective with the new spectrometer.
First X-ray Measurement of Kaonic Deuterium: A Milestone for Low-Energy Strong-Interaction Studies in the Strangeness Sector
Francesco Sgaramella · Thursday, August 20 / plenary
Francesco Sgaramella · Thursday, August 20 / plenary
Kaonic atoms, exotic systems in which a negatively charged kaon replaces an electron, provide a unique laboratory for probing both the strong and electromagnetic interactions. The X-ray transitions emitted during their atomic cascade are modified by the strong interaction in the innermost levels, enabling precision studies of kaon–nucleon and kaon–nucleus interactions and offering direct access to non-perturbative QCD in the strangeness sector. More than four decades ago, Richard Henry Dalitz emphasized that “the most important experiment to be carried out in low-energy K-meson physics is the definitive determination of the energy-level shifts in K − p and K − d atoms, because of their direct connection to the physics of K̄N interaction and their complete independence from all other kinds of measurements which bear on this interaction”. Despite the fundamental importance of the kaonic deuterium measurement, its extreme experimental difficulty has long prevented its realization—until now. The SIDDHARTA-2 collaboration, exploiting the high-quality low-energy kaon beam at the DAΦNE collider in Frascati (Italy) and fast, high-resolution Silicon Drift Detectors (SDDs), has performed the first high-precision X-ray spectroscopy of kaonic deuterium, determining the energy shift and width induced by the strong interaction in the 1s atomic level. These results provide unprecedented constraints on the antikaon–deuteron interaction at threshold energy and advance our understanding of non-perturbative strong interactions in the strangeness sector. In addition, the collaboration has measured transitions in kaonic neon and fluorine, governed predominantly by quantum electrodynamics (QED), providing a unique opportunity to test bound-state QED under extreme electromagnetic fields. In this contribution, I will present the experimental approach, the unique challenges of measuring kaonic deuterium, and the latest results from SIDDHARTA-2. I will discuss their implications for the low-energy strong interaction and outline future perspectives for systematic kaonic atom measurements at DAΦNE and J-PARC, supported by next-generation X-ray detector technologies.
Light hypernuclei
Andreas Nogga · Thursday, August 20 / plenary
Andreas Nogga · Thursday, August 20 / plenary
Hyperon–nucleon (YN), hyperon–hyperon (YY), and three-baryon (YNN) interactions play a crucial role in the understanding of hypernuclear systems. Since scattering data are scarce, light hypernuclei gain tremendous importance for constraining and testing these interactions. I show results based on chiral effective field theory interactions starting with a brief introduction to this approach. Then I present various recent applications including the charge-symmetry breaking of light hypernuclei and their relation to the Λ-neutron interaction and the determination of theoretical uncertainties and the size of YNN forces for s- and p-shell hypernuclei. The estimate of the YNN force is then compared to explicit calculations. Finally, I conclude with a discussion of light strangeness S = −2 hypernuclei and the possibility to gain insight into properties of the YY and ΞN interactions.
High-precision decay-pion spectroscopy of light Lambda hypernuclei at MAMI
Patrick Achenbach · Thursday, August 20 / plenary
Patrick Achenbach · Thursday, August 20 / plenary
The A1 spectrometer facility at the Mainz Microtron (MAMI) is currently the only place worldwide for the high-precision decay-pion spectroscopy of light Λ hypernuclei. In a series of experiments, the monochromatic π − momenta from two-body decays at rest of different hypernuclear isotopes were measured. In the recent 7 Li(e, e′ K + ) electroproduction experiment, the 3Λ H → 3 He +π − decay momentum was determined simultaneously with the 4Λ H →4 He +π − decay momentum achieving unprecedented accuracy. Using the precisely measured Λ binding energy in 4Λ H from earlier campaigns at MAMI, the Λ binding energy in 3Λ H becomes BΛ (3Λ H) = 0.523 ± 0.013 (stat) ± 0.075 (syst) MeV. The measured value indicates a significantly deeper binding than inferred from nuclear emulsion measurements, but is consistent with the result reported by the STAR Collaboration in 2020. This spectroscopic method serves as a unique probe of the baryon–baryon interaction beyond the conventional nucleon-nucleon sector, providing access to hyperon–nucleon and hyperon–hyperon forces that are otherwise difficult to study experimentally.
Examination of the multiple-scattering expansion in four-nucleon and hyperon-deuteron systems
Arnoldas Deltuva · Thursday, August 20 / Session I.1
Arnoldas Deltuva · Thursday, August 20 / Session I.1
The elastic neutron-3H scattering at intermediate energies is studied using rigorous integral equations solved in the momentum-space partial-wave basis. The fourparticle transition operators are expanded into multiple-scattering series in terms of subsystem transition operators [1]. Various approximations resulting from truncation of the series in different ways are evaluated and their validity is investigated. They fail at lower energies but at higher energies provide a rough reproduction of exact results at small scattering angles. In the largeangle region all approximations fail heavily, indicating that the scattering amplitude results from a delicate interplay of many multiple-scattering terms. The partial-wave analysis reveals that the developed approximations are reliable in higher partial waves, and for practical calculations an efficient “hybrid” approach is proposed, combining exact amplitudes in lower partial waves with approximations in higher partial waves. The implications for often used approximation of the first order in two-body transition matrix and development of microscopic optical potentials are discussed. The study is extended to other systems with an opposite behavior, i.e., rather slow convergence of multiple-scattering series, often caused by the presence of resonant states. The examples of the 2nd excited state of 4He tetramer [2], the nonelastic deuteron breakup on a nucleus [3], and two-nucleon + Lambda or Sigma hyperon systems [4] will be presented. 1. Examination of the multiple-scattering expansion in the four-nucleon system A. Deltuva, Phys. Rev. C 111, 024613 (2025) http://dx.doi.org/10.1103/PhysRevC.111.024613 2. Faddeev-type calculation of nonelastic breakup in deuteron-nucleus scattering A. Deltuva, Phys. Lett. B 868, 139825 (2025) https://doi.org/10.1016/j.physletb.2025.139825 3. Second excited state of 4He tetramer A. Deltuva, Phys. Rev. A 113, 013306 (2026) https://doi.org/10.1103/fmpz-xsqq 4. Resonant states in three- and four-body hypernuclear systems R. Lazauskas, A. Deltuva, D. Gazda, M. Schafer, Phys. Lett. B 874, 140214 (2026) https://doi.org/10.1016/j.physletb.2026.140214
Investigation of Three-Nucleon Interactions in Four-Nucleon Scattering
Kimiko Sekiguchi · Thursday, August 20 / Session I.1
Kimiko Sekiguchi · Thursday, August 20 / Session I.1
A few-scattering system offers a good opportunity to study dynamical aspects of three-nucleon forces (3N Fs), which are momentum, spin, and isospin dependent, since it provides not only cross sections but also a variety of spin observables at different incident nucleon energies. Direct comparison between the experimental data and the rigorous numerical calculations based on the realistic bare nuclear potentials provides information on 3N Fs. Indeed, the last two decades have witnessed the extensive experimental and theoretical investigations of the nucleon-deuteron scattering performed in a wide range of incoming nucleon energies up to E¥sim300 ¥rmM eV /nucleon. The four-nucleon (4N ) systems could also play an important role for the study of 3NFs. 3NF effects are expected to be sizable in the 4N system. In addition, while the N d scattering is essentially a pure isospin T = 1/2 state, tests of the T = 3/2 channel in any 3NFs can be performed in a 4N system such as proton-3 He scattering. In Ref. [1] there has been a large progress in solving the 4N scattering problem with realistic Hamiltonian even above four-nucleon breakup threshold energies, which opens up new possibilities for approaching properties of 3NFs. With the aim of exploring the 3NFs in 4N scattering, experiments of proton-3 He scattering using the polarized beam and target systems are in progress in Japan. In the conference, we introduce recently conducted experiments [2,3,4] and present the results of the comparison between the experimental data and the theoretical predictions based on the realistic bare nuclear potentials. [1] A. Deltuva, and A. C. Fonseca, Phys. Rev. C 87, 054002 (2013). [2] A. Watanabe, K. Sekiguchi et al., Phys. Rev. C 103, 044001 (2021). [3] A. Watanabe, K. Sekiguchi et al., Phys. Rev. C 106, 054002 (2022). [4] A. Watanabe, K. Sekiguchi et al., Phys. Rev. C 112, 054001 (2025).
Towards renormalizable description of nuclear processes at very low energies
Martin Schäfer · Thursday, August 20 / Session I.1
Martin Schäfer · Thursday, August 20 / Session I.1
In this work 1, we present an extensive theoretical and numerical study of charged few-nucleon systems (pd, dd, and p − 3 He bound states and scattering) in the framework of pionless effective field theory (EFT) up to next-to-leading order (NLO). We treat the Coulomb interaction nonperturbatively, while NLO interactions, including three-body forces and a four-body force, are treated in perturbation theory. Scattering phase shifts are extracted using recently developed harmonic oscillator trap method for charged projectile and target 2. Special attention is given to renormalization issues. Only a mild cutoff dependence is seen, consistent with the expectations of power counting in pionless EFT. The results hold significant promise for studies of charged-particle scattering at very low energies, with applications to reactions of astrophysical interest. 1 M. Rojik, M. Schäfer, M. Bagnarol, and N. Barnea, Phys. Rev. C 113, 024001, 2026. 2 M. Bagnarol, N. Barnea, M. Rojik, M. Schäfer, Phys. Lett. B 861, 139230, 2025.
Light nuclei collisions from a correlated Gaussian approach
Jérémy Dohet-Eraly · Thursday, August 20 / Session I.1
Jérémy Dohet-Eraly · Thursday, August 20 / Session I.1
More than fifty years ago, the resonating group method (RGM) has been introduced and used successfully to describe nuclear scattering and reactions by using clusterized wave functions. In the traditional approach, the colliding nuclei are described by their groundstate wave function in the shell model. Several generalizations, where the nuclei are described by more elaborate wave functions (using the no-core shell model or correlated Gaussians, for instance), have been developed for transforming the resonating group method into an ab initio approach. In this presentation, I will show a new generalization of the RGM based on centred and decentred correlated Gaussians and apply it to several few-nucleon systems. The advantages (and limitations) of the present method (rather small number of basis functions, analytic evaluation of the matrix elements, easy implementation of different types of clustering, ⋯) with respect to the previous generalizations of the RGM will be emphasized as well as the prospect to apply it up to eight-nucleon systems.
Multineutron correlations in the breakup of Helium-8
Audrey Anne · Thursday, August 20 / Session II.1
Audrey Anne · Thursday, August 20 / Session II.1
Since the discovery of the neutron in 1932 [1], extensive experimental campaigns and calculations have been carried out to explore the possible existence of multineutron systems [2]. The dineutron being unbound, particular attention has been paid to the next even candidate, the tetraneutron, a system made up of four neutrons. Its few-body character and the absence of Coulomb interaction make of this system a perfect case to test nuclear models and the nucleon-nucleon nuclear force. After sixty years of experimental search, with only two promising signals [3,4], the observation of a resonance-like four-neutron structure using a missing-mass approach [5] has rekindled the interest in this field. In this context, the SAMURAI34 experiment aimed at measuring the invariant mass of the four-neutron system using several breakup reactions of an 8 He beam. The direct detection of the four neutrons in different reaction channels will be presented. Preliminary results of several four-neutron observables, and their potential implications, will be discussed. [1] Chadwick, James. “Possible existence of a neutron.” Nature 129.3252 (1932): 312-312. [2] Marqués, F. Miguel, and Jaume Carbonell. “The quest for light multineutron systems.” The European Physical Journal A 57.3 (2021): 105. [3] Marqués, Francisco Miguel, et al. “Detection of neutron clusters.” Physical Review C 65.4 (2002): 044006. [4] Kisamori, K., et al. “Candidate resonant tetraneutron state populated by the he 4 (he 8, be 8) reaction.” Physical review letters 116.5 (2016): 052501. [5] Duer, M., et al. “Observation of a correlated free four-neutron system.” Nature 606.7915 (2022): 678-682.
Short-distance production of multi-neutron systems
Timothy Backert · Thursday, August 20 / Session II.1
Timothy Backert · Thursday, August 20 / Session II.1
Studying short-distance production of multi-particle states provides a powerful theoretical approach to investigate high-energy reactions with low-energy final states in nuclear physics, particularly in hard knock-out reactions such as recent and forthcoming multi-neutron experiments [0,1,2,5,6,7,8,9]. Understanding these states requires an accurate, ideally model-independent, description of their production. Short-distance production is essential, as it is independent of initial distributions and allows direct study of the system and its final-state interactions. For this purpose, effective field theory provides a framework for a model-independent treatment of interactions. We apply this short-distance production framework to systems of three and four neutrons to investigate the possible emergence of multi-neutron resonances. As a first step, we demonstrate that short-distance production is indeed capable of signaling a multi-particle resonance in the case of Efimov resonances. With this benchmark in mind, we then study whether resonance structures appear for three- and four-neutron systems. Consistent with expectations from Schrödinger symmetry [4] and the large charge expansion [11], no resonance-like structure is observed for short-distance production, in agreement with other EFT calculations [10]. However, recent tetraneutron experiments report the observation of a resonance-like structure [2]. As shown by Lazauskas et al. [3], assuming a nonpointlike initial spatial distribution of the four neutrons can lead to a structure compatible with the experimental observations of Duer et al. [2]. To account for this effect, we use our results to obtain final state four-neutron distributions considering some initial neutron distributions. This procedure allows to generate a resonance-like structure. [0] F. M. Marqués and J. Carbonell, The quest for light multineutron systems, Eur. Phys. J. A 57, 105 (2021). [1] R. Y. Kezerashvili, Search of trineutron and tetra-neutron, in 6th International Conference on Fission and Properties of Neutron Rich Nuclei (2016). [2] M. Duer et al., Observation of a correlated free four-neutron system, Nature 606, 678 (2022). [3] R. Lazauskas, E. Hiyama, and J. Carbonell, Low energy structures in nuclear reactions with 4n in the finalstate, Phys. Rev. Lett. 130, 102501 (2023). [4] H.-W. Hammer and D. T. Son, Unnuclear physics: Conformal symmetry in nuclear reactions, Proc. Nat. Acad. Sci. 118, e2108716118 (2021). [5] F. M. Marqués, M. Labiche, A. Orr, N. A., et al., Detection of neutron clusters, Phys. Rev. C 65, 044006 (2002). [6] K. Kisamori, S. Shimoura, H. Miya, et al., Candidate resonant tetraneutron state populated by the 4He(8He,8Be) reaction, Phys. Rev. Lett. 116, 052501 (2016). [7] T. Faestermann, A. Bergmaier, R. Gernhäuser, et al., Indications for a bound tetraneutron, Phys. Lett. B 824, 136799 (2022). [8] K. Miki, K. Kameya, D. Sakai, et al., Precise spectroscopy of the 3n and 3p systems via the 3H(t,3He)3n and 3He(3He,t)3p reactions at intermediate energies, Phys. Rev. Lett. 133, 012501 (2024). [9] T. Faestermann and R. Gernhäuser, Recent results on the tetraneutron, arXiv preprint:2506.11623 (2025). [10] S. Zhang, S. Elhatisari, and U.-G. Meißner, Multi-neutron correlations in light nuclei via abinitio lattice simulations, arXiv:2512.18849 [nucl-th]. [11] S. R. Beane, D. Orlando, and S. Reffert, Unnuclear matter at large charge, Phys. Rev. D 112, 014028 (2025).
Exotic phenomena at the dripline: the most neutron-rich boron isotopes
Emeline Oliveira · Thursday, August 20 / Session II.1
Emeline Oliveira · Thursday, August 20 / Session II.1
The study of nuclei around the neutron dripline allows to investigate surprising or unexpected phenomena that occur at the edges of the nuclear landscape. Neutron-rich nuclei provide access to regimes where the description of states becomes sensitive to nucleon-nucleon interactions, and the structure models to be challenged. In this context, the boron isotopic chain is an ideal case of study as it exhibits a wide variety of structures. Here, we focus on the most neutron-rich boron isotopes 18−21 B. Although they consist of 18 to 21 nucleons, their core+neutron(s) structures allow a description using models with only two or three bodies. First, 18 B is unbound by one-neutron emission and its ground state was characterized as a virtual state 1. In the low-energy scattering formalism within the effective range approximation, the 17 B+n virtual state is described with two parameters : the scattering length as and the effective range re of the interaction 2. At present, we only have an upper limit on the scattering length with as < −50 fm, and the effective range has not been investigated [1, 3]. For comparison, the largest scattering length at the nuclear scale is the neutron-neutron one with as = −18.5 fm and is of the order of several fm for most nuclear systems. If the 17 B+n scattering length were large enough, of hundreds (or even thousands) of fm, 19 B could exhibit universal behavior, including the possible emergence of a phenomenon never observed in nuclear physics : Efimov states [4, 5]. Finally, it is on this already very exotic system that 21 B is built, the last known isotope in the chain. 21 B was found to decay through direct two-neutron emission [6] but correlations between emitted neutrons were not investigated. The structure of these boron isotopes is studied through two experiments conducted at RIKEN Nishina Center (Japan) as part of the SAMURAI collaboration using radioactive beams at ∼ 230 MeV/nucleon sent on a carbon target. 18 B was populated by knockout reactions from 19 C(-p) and 19 B(-n) while 21 B was populated from 22 C(-p). The complete kinematics of the reactions were measured and the reaction products of interest, 17,19 B and neutrons, were respectively detected using the SAMURAI spectrometer and the NEBULA and NeuLAND multineutron detectors. The relative energy spectra of the 17,19 B + xn systems were reconstructed by invariant mass method. The (19 C, 17 B+n) reaction populates only the virtual state, and the large acceptance and high resolution of the SAMURAI setup enabled its full characterization. The first measurement of the effective range of the interaction and the surprisingly large scattering length observed open the way for Efimov physics in 19 B. The (19 B, 17 B+n) reaction populates the virtual state but also two additional resonances. While the latter represents the first spectroscopy of 18 B, the former is found to be very sensitive to the neutron separation energy of 19 B. The population of a 21 B resonant state via the (22 C, 19 B+n+n) reaction and its decay through direct two-neutron emission was confirmed. The investigation of the correlations between emitted neutrons revealed strong neutron-neutron final-state interactions and a suppression of phase space during the two-neutron decay, a behavior that had never been reported in the literature. 1 A. Spyrou et al. Phys. Lett. B 686 (2010) , 129-133 2 F. Miguel Marqués and Emeline Oliveira, EPJ Web of Conf, 311,00006 (2024) [3] S. Leblond, PhD Thesis, Université de Caen Normandie (2015) [4] E. Hiyama et al. Phys. Rev. C 100,011603 (2019) [5] S. Endo et al. Eur. Phys. J. A (2025) [6] S. Leblond et al. Phys. Rev. Lett. 121,262502 (2018)
Two-Neutron Halo Nuclei with Weak Neutron-Core Interaction
Daniel Kromm · Thursday, August 20 / Session II.1
Daniel Kromm · Thursday, August 20 / Session II.1
We investigate the renormalization properties of an EFT scheme for two-neutron halo nuclei with weak neutron-core interaction proposed by Hongo and Son. In this theory, there is a universal prediction for the ratio of the mean-square matter radius and charge radius. We find that one further renormalization input is required to predict both radii separately. Using one of the radii as this input, we quantify the restriction on the UV cutoff from the Landau pole. We apply our results to the case of 22 C as well as other two-neutron halo nuclei and discuss the hierarchy of scales implicit in the power counting. We compare our findings with results obtained from standard Halo-EFT calculations.
Effective theory for strongly attractive one-dimensional fermions
Artem Volosniev · Thursday, August 20 / Session III.1
Artem Volosniev · Thursday, August 20 / Session III.1
Understanding strongly-interacting quantum systems remains one of the main challenges in modern physics. While numerical methods have driven much of the progress in this field, simple and intuitive physical interpretations are often elusive. In this context, analytical solutions – even for toy models – provide invaluable insights. In this work, we study strongly attractive spin-1/2 fermions in one spatial dimension. We begin by solving the few-body problem using the Bethe ansatz, which allows us to derive an effective Hamiltonian that captures the essential physics of the corresponding many-body system. We then map this Hamiltonian onto a weakly interacting model, making it accessible to straightforward analytical techniques. This mapping serves as a powerful tool for analyzing confined systems, which are typically intractable using standard numerical or analytical approaches. As a demonstration, we apply this framework to the Fermi-polaron problem – a single impurity atom immersed in a spin-polarized Fermi gas.
Exact Bethe-ansatz solution under violation of Yang-Baxter conditions
Vladimir Yurovsky · Thursday, August 20 / Session III.1
Vladimir Yurovsky · Thursday, August 20 / Session III.1
Many-body problem solutions admit the Bethe-ansatz (BA) form of a sum of products of singleparticle orbitals from a finite set (see [1] and references therein). Such solutions are applicable to systems with non-diffractive scattering, where a many-body collision can be represented as a sequence of two-body ones. The scattering is non-diffractive whenever the Yang–Baxter consistency conditions (YBC) are satisfied. The Lieb-Liniger-McGuire (LLMG) model of one-dimensional bosons with zero-range δ interactions on a ring satisfies the YBC and has a BA solution. Zero-range interaction hyperplanes divide the coordinate space into sectors. The problem is then solved in the coordinate representation by matching free-particle solutions in adjacent sectors, while the YBC ensure the unambiguity of this matching. Fermi-Bose mapping relates the LLMG model to that of spin-polarized fermions with zero-range δ’ interactions, which describe p-wave scattering in tight atomic waveguides. Consequently, the latter model is expected to admit a BA solution as well. In this case, the solutions in adjacent sectors can be matched, however, direct calculations indicate an apparent violation of the YBC. To independently verify this solution, we solve the Schrödinger equation in the momentum representation. While the coordinate-representation solution consists of matched wavefunctions in different sectors, the momentum-representation solution is global, avoiding ambiguities in matching. Using computer algebra, we have proven that in the momentum representation, the Fermi-Bose mapping of the LLMG solution satisfies the Schroedinger equation with δ’ interactions. This is demonstrated for three non-bound particles and for particle-dimer scattering, as well as for bound states of up to five particles. 1. V. A. Yurovsky, M. Olshanii, and D. S. Weiss, Adv. At., Mol., Opt. Phys. 55, 61 (2008).
Discrete time quantum walk of locally interacting walkers
Vikash Mittal · Thursday, August 20 / Session III.1
Vikash Mittal · Thursday, August 20 / Session III.1
In this work, we introduce a general model for local interactions between quantum walkers conditioned on the internal state of their coins. By choosing their particular case, we systematically study the impact of these interactions on the dynamics of two initially localized and uncorrelated walkers. Our general interaction framework, which reduces to several previously studied models as special cases, provides a versatile platform for engineering quantum correlations with applications in quantum simulation, state preparation, and sensing protocols. It also opens up the possibility of analyzing many-body interactions for larger numbers of walkers.
Cluster Structure of Near-Threshold States with Coulomb plus Short-Range Interactions Based on Compositeness
Tomona Kinugawa · Thursday, August 20 / Session III.1
Tomona Kinugawa · Thursday, August 20 / Session III.1
Near-threshold states have attracted considerable attention in hadron physics, because many exotic hadron candidates are observed near scattering thresholds and are expected to have cluster structures such as hadronic molecules. To investigate their internal structure, we focus on the compositeness, defined as a quantitative measure of the cluster component in the wavefunction [1]. For systems governed only by short-range interactions, shallow bound states tend to be composite dominant as a consequence of the low-energy universality [2], while the near-threshold resonances are non-composite dominant [3]. In realistic systems, however, the constituents may be electrically charged, and the Coulomb interaction can become important in the near-threshold region. Because the Coulomb interaction is long-range, the low-energy universality does not hold in principle, and the nature of cluster dominance near threshold may differ from that in purely short-range systems. In this study, we investigate near-threshold s-wave eigenstates in two-body systems with Coulomb plus short-range interactions based on the compositeness. Using a nonrelativistic effective field theory [4], we study the scattering amplitude, clarify its analytic structure in the complex momentum plane, and formulate the compositeness. We obtain a weak-binding relation in the presence of the Coulomb interaction, where the compositeness is described by the scattering length, the effective range, and the Bohr radius. We find that remnants of the universality still emerge depending on the competition between the Coulomb and short-range interactions, characterized by the ratio of the effective range to the Bohr radius. This implies that near-threshold eigenstates can remain cluster-dominant especially in weak-Coulomb systems, while such dominance is not generally guaranteed when the Coulomb interaction is relatively strong [5]. [1] T. Kinugawa, T. Hyodo, Eur. Phys. J. A 61, 154 (2025). [2] T. Kinugawa and T. Hyodo, Phys. Rev. C 109, 045205 (2024). [3] T. Kinugawa and T. Hyodo, arXiv:2403.12635 [hep-ph]. [4] R. Higa, H. W. Hammer, and U. van Kolck, Nucl. Phys. A 809, 171 (2008). [5] T. Kinugawa and T. Hyodo, arXiv:2604.17813 [hep-ph].
Applications of microscopic optical potentials derived from multiple scattering theory
Matteo Vorabbi · Thursday, August 20 / Session I.2
Matteo Vorabbi · Thursday, August 20 / Session I.2
The optical potential is a well-known and successful tool that is widely used to describe nucleonnucleus scattering processes. Within this approach it is possible to compute the scattering observables for elastic processes across wide regions of the nuclear landscape and extend its usage to inelastic scattering and other types of reactions. A phenomenological approach is usually preferred to achieve a good description of the data; however, it lacks predictive power due to the presence of free parameters contained in the model that need to be fixed. For this reason, we strongly believe that a microscopic approach, completely free from phenomenology, is the preferred tool to make reliable predictions, assess the unavoidable approximations, and provide a clear physical interpretation of the process under consideration. The Watson multiple scattering theory provides a successful framework to derive such optical potential for energies above ~100 MeV. In its simplest formulation, derived at the first order, the optical potential is obtained as the folding integral of the nucleon-nucleon scattering t matrix and the target density. These are the two fundamental quantities of the model and are derived from the same nucleon-nucleon interaction, that is the only input of our calculations. In all our calculations, the target nonlocal density is obtained from different ab initio approaches, such as No-Core Shell Model and Self-Consistent Green’s Function. After a general introduction of the method, we will present results for nucleon-nucleus elastic scattering off light- and medium-mass nuclei at intermediate energies, we will discuss the results of recent extensions of the method at lower energies, as well as the first application of the optical potential to inelastic scattering. We will also present the results obtained from the extension of the method to construct an optical potential to describe nucleus-nucleus elastic scattering.
Stabilisation of few-body resonances to bound states in a continuum
Pascal Naidon · Friday, August 21 / plenary
Pascal Naidon · Friday, August 21 / plenary
In this talk, I will present how few-body resonances can be stabilised to so-called « bound states in a continuum », i.e. resonances with vanishing width that do not decay. The underlying mechanism can be explained by an effective two-channel description. It shows how the lifetime of few-body resonances can be made infinitely long by a continuous tuning of system parameters. I will illustrate this scenario in two different examples: a mass-imbalanced system in one dimension and a system of three identical bosons in three dimensions, relevant to Efimov physics in ultracold atom experiments. Due to the generality of this stabilisation effect, it is expected to be applicable to a wide range of unstable few-body systems.
Measurement of Spin Correlation Coefficients in Polarized Deuteron-Polarized Proton Elastic Scattering
Yuko Saito · Thursday, August 20 / Session I.2
Yuko Saito · Thursday, August 20 / Session I.2
The necessity of three-nucleon forces (3NFs) has been recognized in various nuclear phenomena, including nuclear binding energies and the equation of state of nuclear matter. Consequently, the construction of precise nuclear force potentials including 3NFs remains a major issue in nuclear physics for achieving a comprehensive understanding of atomic nuclei. Nucleon–deuteron scattering, as a three-nucleon system, is an effective probe to investigate 3NFs. Indeed, detailed information on three-nucleon forces has been obtained by directly comparing high-precision nucleon–deuteron scattering data and theoretical predictions based on realistic potentials and ab initio calculations. While agreement between theoretical predictions and experimental data for the differential cross sections can only be achieved with the inclusion of 3NFs, data on spin observables in general still indicate deficiencies in standard 3NF models. To advance the understanding of 3NFs, we have conducted the measurement of spin correlation coefficients in polarized deuteron–polarized proton elastic scattering. Spin correlation coefficients are experimentally demanding spin observables that remain largely unexplored. The obtained data are expected to play a key role in the construction of high-precision 3NF potential based on the modern framework of chiral effective field theory. The experiment was conducted at the RIKEN Radioactive Isotope Beam Factory (RIBF) using an experimental apparatus consisting of the polarized ion source, a solid-state polarized proton target, and the KuJyaku detector, with the latter two specifically developed for this measurement. In this conference, I will present on our measurement of spin correlation coefficients, along with details of the experimental apparatus and preliminary results.
Experimental studies of three-nucleon-system dynamics in proton-deuteron breakup at 108 MeV
Angelina Łobejko · Thursday, August 20 / Session I.2
Angelina Łobejko · Thursday, August 20 / Session I.2
Studies of few-nucleon systems form the basis for understanding nuclear interactions and properties of nuclei. The very accurate theoretical calculations for three-nucleon systems should be confronted with a rich set of precise experimental data. For this purpose, the BINA (Big Instrument for Nuclear-polarization Analysis) detection system has been installed at CCB (Cyclotron Center Bronowice) 1. The BINA setup is designed to study the elastic and breakup reactions at intermediate energies. It consists of the liquid target facility and the low threshold detector covering nearly 4π solid angle, enabling studies of almost full phase space of these reactions [2,3]. The part of the results of the first experimental run of proton-induced deuteron breakup at a beam energy of 108 MeV have been already published [4, 5]. These data will be supplemented with cross section for breakup reaction in configurations near FSI (Final State Interaction) of pp pairs. The data are normalized to the known cross section for proton-deuteron elastic scattering [6]. Differential cross section determined for a set of over 200 kinematic configurations of proton pairs registered in the forward part of BINA will be compared to state-of-the-art theoretical calculations to study the role of the Three Nucleon Force, Coulomb, and relativistic effects. Moreover, the research was extended by introducing a new detector, which enabled the determination of pn pairs from the breakup reaction and their direct comparison with the previously determined pp pairs for selected FSI configurations. The data are important for testing the stateof-the-art calculations and the potentials developed within Chiral Effective Field Theory. 1 A. Łobejko et al., Acta Phys. Pol. B. 50, 3, p.361-366 (2019). 2 St. Kistryn, E. Stephan, J. Phys. G: Nucl. Part. Phys. 40, 063101 (2013). [3] A. Ramazani-Moghaddam-Arani, et al., Phys. Rev. C 78, 014006 (2008). [4] A. Łobejko et al., Few-Body Syst. 65, 2, p.1-7 (2024). [5] A. Łobejko, E. Stephan et al., Phys. Rev. C 111, 054001 (2025). [6] K.Ermisch, et al., Phys.Rev.C 68, 051001 (2005).
First order electroweak radiative corrections to the polarised W boson
Maria Naeem · Thursday, August 20 / Session II.2
Maria Naeem · Thursday, August 20 / Session II.2
Precise theoretical predictions for electroweak processes are essential for fully exploiting the physics potential of current and future collider experiments. Next-to-leading order electroweak radiative corrections to the decay W^+(\uparrow) -> c \bar b of a polarised W boson into a pair of heavy quarks are analysed. The analysis is carried out through the angular distribution of the decay products, with finite fermion masses consistently taken into account throughout the calculation. The nonvanishing masses of the final-state quarks are incorporated and compared with the limit of vanishing quark masses, known as the collinear limit. This comparison highlights the importance of mass effects, which lead to observable deviations from the collinear approximation. These effects provide insight into possible deviations between theoretical predictions and experimental measurements of the total decay rate and branching ratios into massive fermions.
Solving quark-antiquark bound-state equations using the Cornell potential in momentum space
Alfred Stadler · Thursday, August 20 / Session II.2
Alfred Stadler · Thursday, August 20 / Session II.2
The well-known Cornell quark-antiquark potential in momentum space has singularities in both its one-gluon-exchange (OGE) and linear confining parts. These singularities prevent the direct application of the convenient Nyström method to solve the corresponding bound-state integral equation for meson masses. While the Coulomb-type singularity in the OGE potential can be treated with a subtraction technique, only very complicated methods have been developed to deal with the stronger singularity in the linear potential. We present a simple subtraction method to remove this singularity from the kernel, making the Nyström method applicable. The derivatives of the wave function resulting from the subtraction are represented using interpolating functions, and we found Lagrange polynomials to be highly efficient. Test calculations demonstrate excellent agreement with precisely known energy eigenvalues. By increasing the number of integration points and the order of the Lagrange interpolation polynomials, extremely high accuracy can be achieved. We have also extended this method to spin-dependent first-order relativistic corrections of the Cornell potential, which generate spinspin, spin-orbit, and tensor forces. This method is also applicable to relativistic Bethe-Salpeter type equations with singular kernels.
Dynamical generation of charmonium-like tetraquarks via coupled-channel formalism
Heejin Kim · Thursday, August 20 / Session II.2
Heejin Kim · Thursday, August 20 / Session II.2
We investigate the dynamical generation of I = 0 charmonium-like tetraquarks with spin-parity assignments J P C = 0++ , 1++ , 2++ , and 3−− in the mass range of 3.6 to 4.3 GeV. Using an offshell coupled-channel formalism, we construct kernel amplitudes from effective Lagrangians that satisfy heavy-quark spin-flavor and chiral symmetries. To isolate states that are purely dynamically generated, we explicitly exclude s-channel pole diagrams and focus on t- and u-channel meson exchanges. By solving the coupled-channel integral equations, we identify six poles in the complex energy plane. We also discuss their physical properties by determining pole positions and extracting channel coupling strengths. Our results indicate the significant role of coupled-channel effects, in particular the D∗ D̄∗ channel, in the formation of exotic hadrons.
Nonperturbative HQET parameters from the instanton vacuum
Ki-Hoon Hong · Thursday, August 20 / Session II.2
Ki-Hoon Hong · Thursday, August 20 / Session II.2
Heavy-quark effective theory (HQET) factorizes short-distance coefficients from long-distance hadronic matrix elements, but quantitative predictions require reliable information on long-distance QCD dynamics. We employ the QCD instanton vacuum as a low-energy framework that realizes spontaneous chiral symmetry breaking and induces effective nonlocal heavy-light quark interactions. Within this framework, we determine the HQET mass parameter Λ̄, the kinetic-energy parameter λ1 , and the Isgur-Wise function ξ(w), including its zero-recoil slope ρ2 = −ξ ′ (1).
Two-body nonlinear interaction in the bubble surface dark-soliton stability
Lauro Tomio · Thursday, August 20 / Session III.2
Lauro Tomio · Thursday, August 20 / Session III.2
I will report an investigation on the stability of dark soliton in a fixed radius bubble Bose-Einstein condensate, by varying the nonlinear two-body parameter in the corresponding two-dimensional Gross-Pitaevskii formalism. As shown analytically and numerically, snake instabilities occur for angular modes larger than two, which can only decay in the production of vortex dipole pairs. See following reference: R.W. Sallatti, L. Tomio, D. E. Pelinowsky, and A. Gammal, Physical Review A 113, L041303 (2026).
Controllable magneto-trions in buckled two-dimensional materials
Shalva Tsiklauri · Thursday, August 20 / Session III.2
Shalva Tsiklauri · Thursday, August 20 / Session III.2
We investigate the properties of two-dimensional trions in buckled Xene monolayers (silicene, germanene, and stanene) subjected to perpendicular magnetic and electric fields. Within a nonrelativistic effective-mass framework, the three-body Hamiltonian is formulated using the Rytova– Keldysh interaction potential appropriate for screened two-dimensional systems. Employing massscaled Jacobi coordinates, the Hamiltonian is decomposed into magnetic-field-independent, linearin-field, and quadratic-in-field contributions, allowing a systematic analysis of center-of-mass and internal motion coupling. The resulting Schrödinger equation is solved using the hyperspherical harmonics method, yielding converged trion binding energies as functions of magnetic field strength and externally controlled band-gap and effective-mass tuning induced by the electric field. We show that the diamagnetic term leads to a monotonic increase of the ground-state energy with magnetic field, while magnetic stabilization of trions arises from linear-in-field coupling terms that mix center-of-mass and internal degrees of freedom. The interplay between magnetic confinement and electrically tunable effective masses in Xenes enables controlled manipulation of trion binding energies. Intravalley and intervalley trions exhibit distinct magnetic-field dependencies, with enhanced sensitivity to dielectric screening and band-structure asymmetry. The diamagnetic contributions increase the energy monotonically, whereas magnetic stabilization originates from linear-in-field coupling. Our results demonstrate that the combined action of magnetic field and electric-field-induced band-structure engineering enables tunable control of trion states in Xene monolayers.
Beyond Conventional Angular Treatments in Quantum Three-Body Calculations
Anjan Sadhukhan · Thursday, August 20 / Session III.2
Anjan Sadhukhan · Thursday, August 20 / Session III.2
A conceptually distinct, technically straightforward and pedagogically transparent route to the elimination of angular dependence from the non-relativistic three-body Schrodinger equation (SE) is presented. This leads us to the reduced Schrodinger equation (RSE)—a matrix-operator formulation that fully retains the generality of arbitrary particle masses, charges, total angular momentum (L), and parity of the system. The angular basis is constructed from solid minimal bipolar harmonics (MBHs), which naturally preserve the individual partial angular momenta of the constituent particles. The elimination of the angular degrees of freedom from SE, leading to RSE, is achieved without invoking the traditional implementation of irreducible tensor algebra [1, 2], thereby making the approach more accessible. The structure of the resulting RSE also provides immediate insight into the coupling between different partial waves. The derivation of its variational counterpart is presented as well, enabling an accurate computation of bound-state energies and wave functions within correlated basis frameworks. The required angular integrals are evaluated using a novel technique in which MBHs are expressed as linear combinations of Wigner D-functions. Notably, this technique offers a more streamlined and transparent alternative to the conventional evaluation of angular integrals based on Racah-Wigner calculus [3, 4]. Numerical validation of the present derivations is carried out for low-lying singlet and triplet states of the helium atom—both natural parity states (with L ≤ 7) and unnatural parity states (with L ≤ 3). Explicitly correlated multi-exponent Hylleraas-type basis within the framework of the Rayleigh-Ritz variational principle is employed. The proposed method enables an accurate determination of the energy spectra and other physical observables for three-body states with arbitrary angular momentum and parity. This level of generality and precision is particularly relevant in the context of modern high precision experiments, where meaningful comparison between theory and increasingly accurate measurements is essential. Consequently, the approach provides a robust and versatile framework for the interpretation and validation of experimental data in contemporary few-body physics. Furthermore, the formalism not only streamlines the angular reduction for three-body systems but also offers a transparent and systematic foundation for extending such treatments to few- and many-body quantum systems with nonzero angular momentum. References: 1. A.V. Meremianin and J.S. Briggs. The irreducible tensor approach in the separation of collective angles in the quantum N-body problem. Phys. Rep., 384(4):121–195, 2003. 2. V. Efros. The three-body problem: generalized exponential expansion; arbitrary states in a correlated basis, and the binding energy of muonic molecules. Sov. Phys. JETP, 63:5, 01 1986. 3. G. W. F. Drake. Angular integrals and radial recurrence relations for two-electron matrix elements in Hylleraas coordinates. Phys. Rev. A, 18:820–826, 1978. 4. J-L Calais and P-O Lowdin. A simple method of treating atomic integrals containing functions of r12. J. Mol. Spectr., 8(1):203–211, 1962.
Possible solution to the anomalous strength of quadrupole transitions in ²⁰⁸Pb
Gagandeep Singh · Thursday, August 20 / Session III.2
Gagandeep Singh · Thursday, August 20 / Session III.2
The doubly magic nucleus 208 Pb is the archetypal heavy ion system. Yet, there are unresolved questions about its structure. One of these puzzles pertains to the anomalous inelastic scattering populating the 4.086-MeV 2+ 1 level. The measured differential cross-sections for the population of this level in 98-MeV 12 C + 208 Pb and 270-MeV 3 He + 208 Pb inelastic scatterings are underpredicted by the distorted wave Born approximation (DWBA) estimates by about a factor of two [1,2]. This difference between the theory and experiment has been unsolved for about half a century and cannot be attributed to errors in data normalization or the uncertainty in the adopted values of the coupling strengths for the excitation of the concerned 2+ 1 level. Nevertheless, the relatively large level density of 208 Pb in the vicinity of 4\,MeV presents the possibility that the experimental resolution in the measurements mentioned above was insufficient to distinguish between several closely spaced energy levels, some of which might contribute to the measured angular distributions. Thus, assuming an experimental energy resolution of about 200-250\,keV, we calculated differential cross-sections for 98-MeV 12 C + 208 Pb and 270-MeV 3 He + 208 Pb inelastic scattering to the 2+ 1 level, including also eight possibly unresolved levels, viz., the − + − − 3.961-MeV 5− , 4.051-MeV 3 , 4.125-MeV 5− 3 2 4 , 4.144-MeV (22 ), 4.180-MeV 55 , 4.254-MeV 33 , 4.297− + + MeV 56 , and 4.324-MeV 41 , in addition to the 4.086-MeV 21 . A consistent picture was obtained using coupling strengths for these eight levels that were obtained by fitting the 208 Pb(p,p’) data at 35\,MeV [3]. The validation of the resulting values for the Coulomb and nuclear coupling strengths was tested against (p,p’), (d,d’) and (α, α′ ) data [3,4]. The summmed DWBA calculations for these levels were in good agreement with the 98-MeV 12 C + Pb and 270-MeV 3 He + 208 Pb inelastic scattering data, thus providing a plausible explanation of + the anomalously large 0+ 1 → 21 cross section in these data sets. The most important contribution + was from the 41 level; however, although individually weakly populated, the other levels together account for about 20% of the total cross section. 208
References 1 G. R. Satchler et al., Phys. Lett. B 60, 43 (1975). 2 P. P. Singh et al., Pramana - J. Phys. 27, 747 (1986). [3] W. T. Wagner et al., Phys. Rev. C 12, 757 (1975). [4] H. P. Morsch et al., Phys. Rev. C 22, 489 (1980). [5] J. Bojowald et al., Phys. Rev. C 38, 1153 (1988).
References 1 G. R. Satchler et al., Phys. Lett. B 60, 43 (1975). 2 P. P. Singh et al., Pramana - J. Phys. 27, 747 (1986). [3] W. T. Wagner et al., Phys. Rev. C 12, 757 (1975). [4] H. P. Morsch et al., Phys. Rev. C 22, 489 (1980). [5] J. Bojowald et al., Phys. Rev. C 38, 1153 (1988).
Precision studies of the molecular hydrogen ions — a testing ground for fundamental interactions
Stephan Schiller · Friday, August 21 / plenary
Stephan Schiller · Friday, August 21 / plenary
The molecular hydrogen ions are three-body-systems composed of one electron and two light baryons. They are stable and offer a unique potential for both theoretical and experimental investigations at an exceptional level of precision. Indeed, over the last 20 years, the precision has been improved by about a factor 105 , and now has reached the 10−12 fractional level. Because the character of the interactions between the particles and the laws underlying the quantum description of the bound states are believed to be fully known - directly stemming from the Standard Model of Particle Physics - the comparison between theoretical prediction and experimental spectroscopy results provides a novel way of testing those aspects and to search for hypothetical additional interparticle forces, as they may exist in the connection with Dark Matter. In this respect, what sets the molecular hydrogen ions apart from other systems such as the hydrogen atom and the Helium atom system is the strong relevance of the baryon-baryon long-range interaction. Currently, the field is advancing rapidly, both theoretically and experimentally. We will report in particular on the high-accuracy spectroscopy of homonuclear H+ 2 ions in an ensemble [1], and on the first optical spectroscopy of a single molecular hydrogen ion, HD+ . The latter was performed in a strong magnetic field (4\,Tesla). With this experiment and the accompanying theory, we are exploring a three-body system in a novel situation, the presence of a strong magnetic field. The current status of the interpretation of the studies will be presented. [1] S. Alighanbari et al, Nature 644, 69–75 (2025); DOI: /10.1038/s41586-025-09306-2
Experimental studies of Efimov physics in ultracold atoms
Lev Khaykovich · Friday, August 21 / plenary
Lev Khaykovich · Friday, August 21 / plenary
Since the first observation of Efimov physics in ultracold atomic gases nearly two decades ago, the field of fewbody quantum physics has undergone rapid development. Log-periodic scaling, a hallmark of Efimov physics, has been confirmed experimentally in both equal-mass and massimbalanced systems across a variety of observables, while universal relations governing threebody processes have been extensively explored. A key breakthrough was the discovery that van derWaals interactions endow atomic systems with an unexpectedly universal three-body parameter, whose theoretical foundations and limits of applicability have since been clarified [1, 2, 3]. More recently, attention has turned to dynamical and out-of-equilibrium regimes, where intrinsic three-body correlations in unitary Bose gases have been investigated [4, 5]. A complementary line of research has examined systematic departures from van der Waals universality, associated with the character of two-body resonances [6, 7, 8]. Concurrently, two emerging frontiers have opened: (i) coherent few-body physics, in which coherent control and manipulation of Efimov states and related few-body bound states become accessible [9]; and (ii) the RKKY–to–Efimov crossover in fermion-mediated interactions between heavy bosons, which provides a controlled setting to study the transition from long-range, oscillatory RKKY-type interactions to short-range Efimov attraction [10]. In this contribution, I will review these developments, emphasizing the interplay between universality and its breakdown, and highlight how coherent control and fermion-mediated interactions are shaping the next generation of experiments on Efimov and universal few-body physics in ultracold gases. References 1 C. H. Greene, P. Giannakeas, and J. P´erez-R´ıos, Rev. Mod. Phys. 89, 035006 (2017). 2 P. Naidon, and S. Endo, Rep. Prog. Phys. 80, 056001 (2017). [3] J. P. D’Incao, J. Phys. B 51, 043001 (2018). [4] R. J. Fletcher, R. Lopes, J. Man, N. Navon, R. P. Smith, M. W. Zwierlein, and Z. Hadzibabic, Science 355, 377 (2017). [5] C. E. Klauss, X. Xie, C. Lopez-Abadia, J. P. D’Incao, Z. Hadzibabic, D. S. Jin, and E. A. Cornell, Phys. Rev. Lett. 119, 143401 (2017). [6] J. Johansen, B. J. DeSalvo, K. Patel, and C. Chin, Nature Physics 13, 731 (2017). [7] R. Chapurin, X. Xie, M. J. Van de Graaff, J. S. Popowski, J. P. D’Incao, P. S. Julienne, and J. Ye, and E. A. Cornell, Phys. Rev. Lett. 123, 233402 (2019). [8] J. Etrych, G. Martirosyan, A. Cao, J. A. P. Glidden, L. H. Dogra, J. M. Hutson, Z. Hadzibabic, and C. Eigen, Phys. Rev. Res. 5, 013174 (2022). [9] Y. Yudkin, R. Elbaz, J. P. D’Incao, P. S. Julienne, L. Khaykovich, Nature Communications 15, 2127 (2024). [10] G. Cai, H. Ando, S. McCusker, and C. Chin, Phys. Rev. Lett. 136, 083403 (2026).
Positron and Positronium Interactions with Atoms and Molecules
Gleb Gribakin · Friday, August 21 / plenary
Gleb Gribakin · Friday, August 21 / plenary
At the fundamental level, the annihilation of a positron with an electron is described by QED. As such, it allows one to tests QED by comparing high-precision calculations with experiment, e.g., for the lifetime of positronium (Ps), the simplest matter-antimatter “atom”. Positron annihilation and the associated characteristic gamma-ray signal is also a unique probe which provides information on antimatter in the Universe and in our Galaxy. It also lies at the heart of diagnostics, such as PALS (positron annihilation lifetime spectroscopy), used to probe condensed matter systems, and PET (positron emission tomography), a functional medical imagining technique. Hence, in most circumstances positron annihilation takes place in complex atomic or molecular environments, making positron interaction with atoms and molecules an important problem. As it turns out, this interaction is characterised by very strong correlation effects, so it is a challenging theoretical problem. In addition to the usual target polarisation, low-energy positrons also experience attraction due to virtual Ps formation. The combined attraction enables positrons to form bound states with many atoms, a prediction that has not yet been verified in experiment. (Experiments with positrons are also very challenging, though much progress has been made since the creation of positron traps and trap-based positron beams by the group of the late Professor Cliff Surko at the University of San Diego.) For molecules, the existence of bound states leads to a spectacular phenomenon of resonant annihilation. This process involves positron capture accompanied by excitation of molecular vibrations, leading to orders-of-magnitude enhancement of positron annihilation rates in molecular gases. When studied with a high-resolution positron beam, experiment reveals a complex spectrum of vibrational Feshbach resonances (VFR) characteristic of the molecular species. In addition to simple single-quantum vibrations, these spectra contain signatures of multimode vibrations, and the observed level of enhanced annihilation points to the importance of intramolecular vibrational energy redistribution. When interacting with matter, positrons can ionise it by forming Ps. This gives rise to a range of questions concerning Ps scattering from atoms and molecules, and the accompanying process of pick-off annihilaton. Theoretical progress in this area is impeded by both the projectile and target being composite particles, so much of the experimental data remains poorly understood. In my talk I will review the current state of understanding of these phenomena, including recent advances in the application of many-body-theory methods to positron-molecule interactions, calculations of positron binding and VFR spectra, and collisions involving positronium.
Antihydrogen studies
Stefan Eriksson · Friday, August 21 / plenary
Stefan Eriksson · Friday, August 21 / plenary
The comparison of bound-state energy spectra of hydrogen and antihydrogen constitutes a stringent test of fundamental symmetry such as Lorentz and CPT invariance 1. The availability of excitable transitions in combination with frequency metrology can be harnessed for precision measurements of energy intervals in both matter and antimatter species. The precisely determined energy spectra and a theoretically tractable structure allow for a straightforward interpretation of results. Since hydrogen and antihydrogen are charge neutral, effects from environmental noise are reduced, and motion under the influence of gravity can be studied despite the small effects arising in laboratory conditions on Earth. Here, the comparison of behaviour between the matter and antimatter species constitutes a test of the Weak Equivalence Principle. In this presentation I will review the progress of antihydrogen studies in the Antimatter Factory at CERN. The field has been transformed from initial proof-of-principle synthesis and trapping of antihydrogen to precision measurements. This transformation is underpinned by the new ELENA source of low energy antiprotons 2, the production of substantial samples of anti-atoms by sympathetic cooling with laser cooled beryllium ions [3], laser cooling of antihydrogen [4], and the integration of a primary frequency reference [5] in the ALPHA experiment at CERN. The hyperfine components of the 1S-2S two-photon transition in trapped antihydrogen can now be measured in one day [6] and the effect of gravity on the motion of antimatter has been observed [7]. I will present the most recent results and an outlook of antihydrogen spectroscopy and gravitational studies. I will conclude with the prospects of the synthesis and ultraprecise spectroscopy of antihydrogen molecular ions for future improvements of fundamental symmetry tests. 1 M. Charlton, S. Eriksson, G. M. Shore, Antihydrogen and Fundamental Physics (Springer Cham, 2020) (https://arxiv.org/abs/2002.09348). 2 C. Carli et al, ELENA: Bright Perspectives for Low Energy Antiproton Physics, Nuclear Physics News 32 21 (2022). [3] R. Akbari et al. (ALPHA Collaboration), Be+ assisted accumulation of more than 15000 antihydrogen atoms. Nature Communications 16 10106 (2025). [4] C. J. Baker et al. (ALPHA Collaboration), Laser cooling of antihydrogen atoms. Nature 592, 35-42 (2021). [5] J. Nauta et al. Evaluation of a caesium fountain frequency standard for antihydrogen spectroscopy Metrologia 62 045008 (2025). [6] C. J. Baker et al. (ALPHA Collaboration), Precision spectroscopy of the hyperfine components of the 1S–2S transition in antihydrogen. Nature Physics 21 201 (2025). [7] E. K. Anderson et al. (ALPHA collaboration), Observation of the effect of gravity on the motion of antimatter, Nature 621 717 (2023).
Ultracold chemistry as a testbed for few-body physics
Tijs Karman · Friday, August 21 / plenary
Tijs Karman · Friday, August 21 / plenary
Ultracold atoms, molecules and ions provide a unique playground to explore chemistry at ultracold temperatures. These systems are particularly appealing as controlled quantum systems. The multiscale nature of these systems that emerges from the multitude of relevant energy and length scales, as well as the high density of states of collision complexes, pose theoretical challenges. I will discuss recent progress in the field, focusing on chemical processes such as bimolecular chemical reactions, three-body recombination, photochemistry, and the control of these processes by “collisional shielding”. We emphasize the synergy between theory and experiment, highlighting the predictive power of theory and future directions in ultracold chemistry research. 1 Karman, Tomza, Perez-Rios Nature Physics 20, 722 (2024)
Role of the ⁵He nuclear structure in the limitations of gamma-ray diagnostics for fusion power monitoring in tokamaks
Giulia Marcer · poster
Giulia Marcer · poster
In controlled nuclear fusion, the D + T → n + α fusion reaction is the leading option due to its highest cross section at the lowest center-of-mass energies. In magnetic confinement experiments, the fusion power of a Deuterium-Tritium (DT) plasma can be reliably assessed only through neutron counting, since neutrons, being uncharged, escape the magnetic field and are detected by external neutron diagnostics. Although the DT reaction features additional decay channels, at the reactants energies relevant to fusion devices (tens of keV) these branches are strongly suppressed, resulting in a 1:1 correlation between emitted neutrons and fusion reactions. Though, a second neutron-independent diagnostic technique is required for future reactor licensing and would provide a valuable tool for benchmarking scientific results and improving the accuracy of fusion power measurements. A novel approach has recently been developed based on the detection of gamma-rays emitted in two secondary branches of the DT reaction. In these channels, the intermediate ⁵He nucleus de-excites radiatively rather than promptly decaying into neutron and alpha particle. However, this method is affected by a significant limitation. The absolute probability of the radiative branches at the relevant reactant energies is extremely low and poorly known: values reported in the literature span a factor of 20, ranging from 1.3 × 10⁻⁵ to 2.8 × 10⁻⁴. The same holds for the gamma-rays energy spectrum distribution. These uncertainties currently prevent fusion power from being determined through this novel technique in fusion experiments. This poster presents the work carried out at the tokamak JET during its second DT campaign, in 2021, to achieve the most precise spectroscopic measurement of the DT radiative emission and the only determination to date of its branching probability in magnetic confinement experiments. The study demonstrates that the measurement is severely affected by an unavoidable neutron-induced background, approximately 10⁵ times more intense, which overwhelms the DT signal, preventing its precise identification and leading to a 20% uncertainty in the DT gamma-ray intensity and, consequently, in the inferred fusion power. The novelties and limitations of the obtained results are discussed, emphasizing the necessity of an accurate nuclear-structure model of ⁵He to render this diagnostic technique fully viable.
Clothed-particle eigenstate problem with 2N and 3N quasipotentials
Yan Kostylenko · poster
Yan Kostylenko · poster
In previous research [1] devoted to the introduction of three-nucleon (3N ) forces in the theory of few-nucleon systems, we emphasized the need to reconcile the 2N and 3N interaction operators when calculating the corresponding observables. Such an inconsistency is inherited in Refs. [1,2], i.e., the Kharkiv 2N potential [3] is used together with the Tucson-Melbourne 3N potential [4]. In this context, we start with a primary Hamiltonian H with Yukawa couplings V between meson (π, η, ρ, ω, δ, σ) and nucleon (antinucleon) fields. Using the special unitary transformation we rewrite H in the clothed-particle representation (CPR), where all one-clothed-particle states are eigenvectors of H. In [3] it has been shown how such an approach allows us to build up Hermitian and energy–independent 2N potential that embodies off-energy-shell and relativistic effects. Along with the fruitful applications [1–3] and [5–7] of the Kharkiv potential we show our recent results in constructing the operators of 3N interaction in the CPR. In this framework, the leading order 3N contributions stem from the third order commutator [R, [R, [R, V ]]], where R is antihermitian generator of the unitary clothing transformation. In the course of our field-theoretical treatment, we have shown that the 3N eigenvalue equation with interaction operators between clothed nucleons can be represented by a typical Faddeev construction ( ) ∑3 HF + i=1 (Vi + Wi ) |Ψ⟩ = E|Ψ⟩, where Vi and Wi are made up of three-nucleon matrix elements originated from our 2N and 3N interaction operators, respectively. The role of the corresponding 2N forces in the three-body problems has been shown in detail in the recent paper [7]. Also, we would like to address a convenient form { } ∑ ∑ ∑ k (k k )k W1 = k κ k1 k23 k2 k3 {Sk2 (2) ⊗ Sk3 (3)}k23 ⊗ Sk1 (1) kκ Ŵkκ23 2 3 1 that is generated after separating the spin content of the obtained interactions. We use the definition of the spin-tensor operators S(i) (i = 1, 2, 3) from the compendium [8]. Recall, the irreducible tensor product {Sk2 (2) ⊗ Sk3 (3)}k23 itself is the spin-tensor for the system of two particles with k
(k k )k1
indices 2 and 3. Tensors Ŵkκ23 2 3 interaction operator in the CPR.
are determined through the matrix elements of the 3N
Our 3N forces are compared with those by Coon and Han [4]. References 1. A. Arslanaliev, J. Golak, H. Kamada, A. Shebeko, R. Skibiński, M. Stepanova, H. Witała, Phys. Part. Nucl. 53 (2022) 87-95; 2. A. Arslanaliev, P. Frolov, J. Golak, H. Kamada, A. Shebeko, R. Skibiński, M. Stepanova, H. Witała, Few-Body Syst 62 (2021) 71; 3. I. Dubovyk, A. Shebeko, Few-Body Syst 48 (2010) 109–142; 4. S. Coon, H. Han, Few-Body Syst. 30 (2001) 131; 5. A. Shebeko, E. Dubovik, Few-Body Syst 54 (2013) 1513–1516; 6. H. Kamada, A. Shebeko, A. Arslanaliev, Few-Body Syst 58 (2017) 70; 7. H. Kamada, A. Arslanaliev, Y. Kostylenko, A. Shebeko, J. Golak, R. Skibiński, K. Topolnicki, V. Chahar, D. Ramírez Jiménez, H. Witała, W. Polyzou, arXiv:2601.00534 [nucl-th] (2026), to be published in Physical Review C;
8. V. Khersonskii, A. Moskalev, D. Varshalovich, Quantum Theory Of Angular Momentum, World Scientific Publishing Company, Singapore, 1988.
(k k )k1
indices 2 and 3. Tensors Ŵkκ23 2 3 interaction operator in the CPR.
are determined through the matrix elements of the 3N
Our 3N forces are compared with those by Coon and Han [4]. References 1. A. Arslanaliev, J. Golak, H. Kamada, A. Shebeko, R. Skibiński, M. Stepanova, H. Witała, Phys. Part. Nucl. 53 (2022) 87-95; 2. A. Arslanaliev, P. Frolov, J. Golak, H. Kamada, A. Shebeko, R. Skibiński, M. Stepanova, H. Witała, Few-Body Syst 62 (2021) 71; 3. I. Dubovyk, A. Shebeko, Few-Body Syst 48 (2010) 109–142; 4. S. Coon, H. Han, Few-Body Syst. 30 (2001) 131; 5. A. Shebeko, E. Dubovik, Few-Body Syst 54 (2013) 1513–1516; 6. H. Kamada, A. Shebeko, A. Arslanaliev, Few-Body Syst 58 (2017) 70; 7. H. Kamada, A. Arslanaliev, Y. Kostylenko, A. Shebeko, J. Golak, R. Skibiński, K. Topolnicki, V. Chahar, D. Ramírez Jiménez, H. Witała, W. Polyzou, arXiv:2601.00534 [nucl-th] (2026), to be published in Physical Review C;
8. V. Khersonskii, A. Moskalev, D. Varshalovich, Quantum Theory Of Angular Momentum, World Scientific Publishing Company, Singapore, 1988.
Polarized solid proton target for spin correlation coefficients measurement of deuteron–proton elastic scattering at 100 MeV/nucleon
Daichi Takahashi · poster
Daichi Takahashi · poster
Achieving a unified understanding of nuclear phenomena based on nuclear forces requires detailed information on three-nucleon forces (3NFs), especially their spin-dependent parts. To this end, we propose a high-precision measurement of spin correlation coefficients in deuteron-proton elastic scattering at 100 MeV/nucleon at RIKEN. To reliably extract 3NF effects from these measurements, the polarized target must be in a solid state and maintain a proton polarization of at least 0.10 under beam irradiation with an intensity of 108 counts/s (cps). In this work, we developed a polarized solid proton target and conducted a scattering experiment using a polarized deuteron beam and the polarized proton target to demonstrate its performance. The polarized target employs dynamic nuclear polarization using photoexcited triplet electrons (Triplet-DNP), which transfers electron spin polarization to protons via microwave irradiation. The target dimensions were ϕ10 mm × 2.5 mm, and the system was operated at 0.4 T and 285 K. In a previous experiment conducted in January 2024, a p-terphenyl single crystal doped with 0.01 mol\% pentacene-d14 was used, yielding a proton polarization of only 0.03. In the present study, p-terphenyl-d4 was introduced and a new Triplet-DNP system was developed to improve the polarization. A polarized d-polarized p elastic scattering experiment was carried out at the RIKEN RIBF in January 2026 using both p-terphenyl-d4 and p-terphenyl crystals. The polarized deuteron beam was produced using a polarized ion source and d-p elastic scattering was measured with the KuJyaku detector. From the measured scattering asymmetry, the target polarization was determined to be 0.126±0.007stat. ±0.005syst. for the p-terphenyl-d4 crystal and 0.057±0.004stat. ±0.002syst. for the p-terphenyl crystal. For the p-terphenyl-d4 crystal, the initial polarization before beam irradiation was estimated to be lesssim0.14, representing a substantial improvement over the previous experiment. Using the extracted target polarization, the proton analyzing power ATy was derived at various scattering angles and found to be consistent with theoretical calculations. Depolarization under beam irradiation with an intensity of 3–5×107 cps was observed, resulting in a reduction of the polarization to 0.08 after approximately 80 hours. Toward a precise determination of three-nucleon forces (3N Fs), this study represents a significant breakthrough in achieving high polarization in a large single-crystal solid proton target. With respect to radiation-induced depolarization, future efforts will focus on optimizing the pentacene concentration and the laser system. These improvements are expected to realize polarized targets capable of maintaining high polarization under high-intensity beam irradiation, thereby establishing a solid experimental pathway toward a comprehensive determination of three-nucleon forces.
Software Testing in Few-Body Systems Physics
Shuhei Ohno · poster
Shuhei Ohno · poster
Open-source software (OSS) development is a modern and collaborative way to meet the diverse software requirements in few-body systems physics. Our challenge is to build CI/CD with automated testing as a baseline requirement for maintainability and for accepting external contributions. We address this challenge by using two testing methodologies: oracle-based testing and differential testing. For established benchmark problems, the final outputs can be validated using a database of results compiled from the literature (oracle-based testing). For previously unexplored problems, cross-method comparisons, as in a previous study of a four-nucleon bound state (Phys. Rev. C 64, 044001), are effective (differential testing). Currently, we are building an open-source ecosystem in the Julia programming language as a shared infrastructure with reusability and extensibility based on these two testing approaches. At the conference, we will present our overall architectural design and long-term development roadmap derived from testability.
Preparing a Polarized Deuteron Beam for the Measurement of Spin-Correlation Coefficients in Deuteron–Proton Elastic Scattering at 100 MeV/nucleon
Hiroki Sugahara · poster
Hiroki Sugahara · poster
Three-nucleon forces (3NFs) play a crucial role in describing a range of nuclear phenomena. However, the spin-dependent properties of 3NFs remain incompletely understood. To further investigate these properties, we have initiated a project to measure spin-correlation coefficients in deuteron-proton (d-p) elastic scattering at 100 MeV/nucleon at RIKEN RIBF. The measurements require both a polarized beam and a polarized target. Since 2023, we have been upgrading and preparing the Polarized Ion Source (PIS) at RIBF, which provides vector- and tensor-polarized deuteron beams. Preliminary tests using only the AVF cyclotron confirmed that the beam polarization met the requirements for the spin-correlation coefficient measurements. Building on these preparations, we successfully conducted spin-correlation coefficient measurements in January 2026. In this campaign, we commissioned a beamline polarimetry system. The obtained beam polarizations were py = −0.615 ± 0.005 and pyy = 0.896 ± 0.012, demonstrating high stability and performance. In this contribution, we report on the preparation of the PIS and the beamline polarimeter, provide details of the experimental setup, and present the spin observables obtained for d-p elastic scattering at 100 MeV/nucleon.
Propagation of optical vector vortices in coherently prepared media
Hamid Reza Hamedi · poster
Hamid Reza Hamedi · poster
We investigate the propagation of an optical vector vortex weakly interacting with a coherently prepared atomic medium in a three-level Lambda configuration. The vector beam consists of vortex pulse pairs with right- and left-circular polarizations, corresponding to opposite spin angular momenta (SAMs) and carrying opposite orbital angular momentum (OAM) charges ±l. We show that during the propagation of the vortex pairs, analytically obtained in the linear regime, the medium inherits the topology of the vortex pair, mapping the OAM onto a spatially structured atomic coherence. This mapping produces 2|l|-fold azimuthal transparency structures that reshape the beam intensity from a ring into a petal-like pattern. The OAM-structured atomic coherence induces a corresponding optical anisotropy within the medium, which feeds back into the propagating vector beam, resulting in optical spin-orbit coupling manifested as SAM exchange, rotation, and evolution of polarization textures. Depending on the initial ground-state population of the phaseonium, the polarization state evolves between left-circular, linear, and right-circular polarizations. 1 1 Dharma P. Permana, Mazena Mackoit Sinkevičienė, Julius Ruseckas, and Hamid R. Hamedi, Phys. Rev. A 113, 043705 (2026)
Bound-state energies of the three-body Coulomb systems in bulk semiconductors
Pavel Belov · poster
Pavel Belov · poster
Trions, or so-called charged excitons, are bound states of three-body Coulomb systems in semiconductors 1. These electron-hole complexes consist of either two holes and one electron (X + trion) or two electrons and one hole (X − trion). In this work, we compare different approaches to calculate the energy levels of trions in bulk crystals for a broad range of electron-hole mass ratios, covering most of the semiconductor compounds. Within the effective Hamiltonian model, we employ the variational calculations with predefined trial functions 2, the numerical methods based on the total angular momentum representation of the wave function [3,4], as well as upon an expansion over the Laguerre polynomials in perimetric coordinates [5]. These methods allow us to accurately determine spectra of trion energies for various electron-hole mass ratios, including regimes for which the Born-Oppenheimer approach [6,7] is inapplicable. We demonstrate how the energy levels change during the crossover from a very small electron-hole mass ratio to a large one, i.e. the evolution of the system properties from a positively charged hydrogen molecule ion with many vibrational levels [8] to an analogue of a negatively charged hydrogen ion with only one bound state [9]. We extend and improve upon the recent numerical results obtained for the X − trion in Ref. [10]. 1 R. Y. Kezerashvili, Few-Body Syst. 60 (2019) 52. 2 V. I. Korobov and J. Buša, Comp. Phys. Comm. 319 (2026) 109920. [3] V. V. Kostrykin, A. A. Kvitsinsky, and S. P. Merkuriev, Few-Body Syst. 6 (1989) 97. [4] N. Elander and E. Yarevsky, Phys. Rev. A 56 (1997) 1855. [5] E. Z. Liverts and N. Barnea, Comp. Phys. Comm. 184 (2013) 2596. [6] M. Born and R. Oppenheimer, Ann. d. Phys. 389 (1927) 457. [7] L. Happ, et al., Phys. Rev. A 100 (2019) 012709. [8] H. Wind, J. Chem. Phys. 43 (1965) 2956. [9] R. N. Hill, J. Math. Phys. 18 (1977) 2316. [10] R. Combescot, Phys. Rev. B 100 (2019) 245201.
The clothing procedure using a φ³ interaction on the light front
Brady Martin · poster
Brady Martin · poster
In quantum field theory, clothed particles are obtained by dressing bare particles using interactions. In the clothed particle representation, there are self-energy and cloud effects that lead to mass renormalization and vertex terms. The clothing procedure allows one to express the original Hamiltonian that depends on a set of bare creation/destruction operators in a new functional form that depends on a set of clothed-particle operators, and the procedure allows one to remove divergent terms directly from the Hamiltonian in a purely algebraic manner. The key idea behind this transformation from a bare particle representation to a clothed particle representation is to obtain a representation where the physical vacuum state and one-clothed-particle states are both eigenvectors of the total Hamiltonian. During the poster session, I will present work showing how the clothing procedure can be performed using a phi^3 interaction on the light-front. I will focus on how the clothing procedure can be used to obtain a two-body interaction by carrying out the procedure to second order, and I will also discuss how the light-front vacuum is affected by the final result. * This work is funded by the National Science Foundation (NSF).
From Scale Invariance to Universal Droplets: Generalised GPE for Attractive 2D Bose Gases
Michał Suchorowski · poster
Michał Suchorowski · poster
Dilute two-dimensional (2D) gases exhibit scale-invariant behaviour that is absent in their threedimensional counterparts. In attractive systems, this symmetry can be strongly broken —a phenomenon known as the quantum anomaly —by the presence of universal many-body bound states (droplets). To explore this anomaly, especially the corresponding time dynamics, a simple yet powerful theoretical tool is required. In this work 1, we introduce a density-dependent coupling based on the few-body properties of the system into the Gross-Pitaevskii equation (GPE), which not only captures the quantum anomaly but also retains a structure suitable for both intuitive analytical and numerical analysis. In my talk, I will demonstrate how this approach naturally bridges the physics of trapped systems and self-bound droplets, and how it enables the investigation of excited states and complex collective dynamics. 1 Suchorowski M., Brauneis F., Hammer H-W., Tomza M., Volosniev A. G., 2025, preprint arXiv:2511.10115
Dynamics of electron–molecule resonances probed by 2D electron-energy-loss spectroscopy
Juraj Fedor · poster
Juraj Fedor · poster
We address a decay dynamics of transient anions (resonances) formed in electron molecule collisions. Typically, a lifetime of such a resonance towards electron detachment, determined by the centrifugal barrier, lies in a femto- to pico-second time domain. In polyatomic molecules and in clusters, an efficient intramolecular vibrational redistribution (IVR) prior to the electron detachment can lead to the electronic stabilization of the resonance and create a vibrationally hot molecular anion. The total energy of such complex lies in the continuum and it can decay via competing statistical processes. Our main experimental tool is 2D electron energy loss spectroscopy. There we control energy of the incident electrons, collide them with the target and monitor the outgoing energy of scattered electrons. By recording the spectra at many incident energies we construct 2D maps which provide a comprehensive picture of the nuclear dynamics on resonances. One part of my contribution will cover excitation of specific vibrational modes. Already in such a small polyatomic molecule such as CO2 the dynamics is strongly non-Born-Oppenheimer and proceeds on a number of states strongly coupled via continuum. Another part will focus on processes involving IVR and slow-electron emission. This effect is observed in number of molecules and can be described by the Weisskopf model for particle emission which is based on the detailed balance principle.
Coherent Control of Ultrafast Molecule Making from a Pair of Atoms
Zohar Amitay · poster
Zohar Amitay · poster
Coherent control of ultrafast molecule making from a pair of colliding reactants is of fundamental interest both in its own right and as a crucial component of coherent control of binary photoreactions. Realizing such control will also enable a novel type of photochemistry. To handle diverse excitation scenarios, feasibility with both weak and strong fields is essential. Previously, we have demonstrated the strong-field feasibility. Here, we experimentally demonstrate the weak-field feasibility, achieving it even under thermally hot conditions. The making of KAr complexes from gas-phase pairs of colliding K and Ar atoms at a temperature of 493 K via resonance-mediated two-photon excitation (K+Ar+2hν→KAr∗ ) is coherently controlled by weak linearly chirped femtosecond pulses 1. Our ab initio theoretical studies are in excellent agreement with the experiments and explain them. This allows us to identify the control mechanism and utilize it to further enhance the degree of coherent control by fine-tuning the exciting pulse spectrum 2. Beyond its direct significance, the demonstrated control of the KAr system also serves as a basic model for controlling triatomic systems (with an atom and a diatomic molecule as the reactants) that are nonreactive in their ground electronic state and whose excited electronic states are weakly bound or unbound. All these results open up new routes toward the realization of coherent control of binary photoreactions. 1 M. Geva, Y. Langbeheim, A. Landau and Z. Amitay, Phys. Rev. Lett. 133, 193201 (2024). 2 M. Geva, A. Landau and Z. Amitay, in preparation.
Molecular R-matrix approach: from few-body systems to collective processes in multi-electron molecules
Martin Crhán · poster
Martin Crhán · poster
For several decades, the molecular R-matrix method and its implementation, UKRmol+ [1] have been used to study electron collisions with molecules and molecular photoionization. In recent years the suite has undergone a rapid development. This includes the implementation of the multi-photon R-matrix approach [2] for studies of attosecond electronic dynamics [3] and the inclusion of effective core potentials [4] which paves the way to studies of continuum dynamics in molecules containing heavy atoms [5]. A time-dependent extension of UKRmol+, R-matrix method with Time (RMT) [6], has been developed to probe processes in strong and ultrafast external fields [7].
The updated toolkit has allowed us to provide a deep insight into laser-driven processes in molecules. This includes, for example, the discovery of new types of laser-driven quantum mechanical interferences which manifest as the electronic coupling delay [8] and dipole-laser coupling delay [9]. They are general processes appearing in systems from small, such as LiH, to heavy-atom molecules such as CHI. Further studies of higher-order multi-photon processes has led to the formulation of powerful approximations to multi-photon matrix elements [10] reducing computational time by orders of magnitude.
Recently, we have started to extend the suite to include relativistic effects such as spin-orbit coupling. In this contribution we show the progress in this direction on several examples from model systems to I molecule and CHI. In heavy atom-molecules such as CHI, we probe the collective phenomena triggered by photoionization of the 4d shell of iodine atom which leads to the formation of the Giant Dipole Resonance (GDR), an analogue of the collective processes known from nuclear physics.
References
[1] Z. Mašín et al., Comput. Phys. Commun. 249, 107092 (2020).
[2] J. Benda, Z. Mašín, Sci. Rep. 11, 11686 (2021).
[3] I. Makos et al., Nat. Commun., 16 8554 (2025).
[4] Z. Mašín et al., J. Chem. Theory Comput., 22 1563 (2026).
[5] A. L. García-Muñoz et al., Plasma Sources Science and Technology, Accepted, (2026).
[6] A. C. Brown et al., Comput. Phys. Commun. 250 107062 (2020).
[7] J. Benda, et al., Phys. Rev. A 102, 052826 (2020).
[8] J. Benda et al., Phys. Rev. A 111, 013110 (2025).
[9] J. Benda, and Z. Mašín, Phys. Rev. A, 109, 013106 (2024).
[10] J. Benda et al., Phys. Rev. A, 111, 013110 (2025).
The updated toolkit has allowed us to provide a deep insight into laser-driven processes in molecules. This includes, for example, the discovery of new types of laser-driven quantum mechanical interferences which manifest as the electronic coupling delay [8] and dipole-laser coupling delay [9]. They are general processes appearing in systems from small, such as LiH, to heavy-atom molecules such as CHI. Further studies of higher-order multi-photon processes has led to the formulation of powerful approximations to multi-photon matrix elements [10] reducing computational time by orders of magnitude.
Recently, we have started to extend the suite to include relativistic effects such as spin-orbit coupling. In this contribution we show the progress in this direction on several examples from model systems to I molecule and CHI. In heavy atom-molecules such as CHI, we probe the collective phenomena triggered by photoionization of the 4d shell of iodine atom which leads to the formation of the Giant Dipole Resonance (GDR), an analogue of the collective processes known from nuclear physics.
References
[1] Z. Mašín et al., Comput. Phys. Commun. 249, 107092 (2020).
[2] J. Benda, Z. Mašín, Sci. Rep. 11, 11686 (2021).
[3] I. Makos et al., Nat. Commun., 16 8554 (2025).
[4] Z. Mašín et al., J. Chem. Theory Comput., 22 1563 (2026).
[5] A. L. García-Muñoz et al., Plasma Sources Science and Technology, Accepted, (2026).
[6] A. C. Brown et al., Comput. Phys. Commun. 250 107062 (2020).
[7] J. Benda, et al., Phys. Rev. A 102, 052826 (2020).
[8] J. Benda et al., Phys. Rev. A 111, 013110 (2025).
[9] J. Benda, and Z. Mašín, Phys. Rev. A, 109, 013106 (2024).
[10] J. Benda et al., Phys. Rev. A, 111, 013110 (2025).
Photoproduction of eta prime mesons off protons in the resonance region
Denisa Trnková · poster
Denisa Trnková · poster
We use isobar models to describe the γp → η′p process. The amplitude is constructed as a sum of tree-level Feynman diagrams with proton and nucleon resonance exchanges in the s and u channels and ρ and ω meson exchanges in the t channel. The free parameters of the models are fitted to differential cross section and photon-beam asymmetry data. Three different isobar models are compared with the experimental data, and the roles of the individual resonances are discussed. We find the N(1875)3/2⁻, N(1895)1/2⁻, N(1900)3/2⁺, N(2100)1/2⁺, and N(2120)3/2⁻ states to be the most important for achieving a good description of the data. Predictions for the recoil-proton and target polarization asymmetry are also presented.
A study of the electromagnetic and gravitational form factors of nucleon and Δ(1232).
Yubing Dong · poster
Yubing Dong · poster
In this work, a systematical study of the electromagnetic (EM) and gravitational form factors of nucleon and Δ isobars are given. The calculations is based on the quark-diquark approach¹·² and in particular, the pion meson cloud effect is taken into account³. Our results show the important effect of the cloud effect on a interpretation of the EM form factors and the gravitational form factors of the systems. It is found that the effect changes the sign of the D-term, and makes our results to be consistent with the experimental data and other model calculations. [1] Dongyan Fu, Baodong Sun, and Yubing Dong, Phys. Rev. D105, 096002. [2] Jiaqi Wang, Dongyan Fu, and Yubing Dong, Eur. Phys. J. C 84, 79. [3] Jiaqi Wang, Dongyan Fu, and Yubing Dong, Eur. Phys. J. C 85, 1254.