Mon·Mar 10, 2025Monday·March 10, 2025

1. 01*

   Investigation of Direct Nuclear Reactions in a Storage Ring Using In-Ring Detection

   J. C. Zamora🇺🇸 · T. Aumann🇩🇪 · S. Bagchi🇩🇪 · S. Bishop · M. Bo · S. Bonig · C. Brandau🇩🇪 · M. Csatlos🇭🇺 · T. Davinson🇬🇧 · I. Dillmann🇨🇦 · C. Dimopoulou · D. T. Doherty🇬🇧 and 53 other authors

   \textbf{Background:} Experiments involving nuclear reactions in a storage ring offer exceptional possibilities for precise measurements in inverse kinematics. These experiments provide excellent angular and energy resolution by particle spectroscopy, in addition to high luminosities. However, the extremely low-pressure environment maintained in the storage rings poses significant difficulties for experiments employing detectors or any outgassing material in the ring. \textbf{Purpose:} To investigate nuclear reactions in inverse kinematics using the storage-ring technique. The reactions were induced by scattering of a ${}^{20}\mathrm{Ne}$ beam off a hydrogen target at an energy of 50~MeV/u. \textbf{Method:} A beam of fully stripped ${}^{20}$Ne ions was injected into the ESR storage ring at an energy of 50 MeV/u. The beam interacted with an internal hydrogen gas-jet target. An ultra-high vacuum compatible detector setup was installed around the gas jet inside the ring to measure the recoiling particles generated by nuclear reactions. \textbf{Results:} Multiple reaction channels were observed during the experiment. In particular, we present the results from studies on elastic and inelastic scattering, as well as the neutron transfer reaction ${}^{20}\mathrm{Ne}(p,d){}^{19}{\mathrm{Ne}}^{\ast }$. The experimental data were compared to calculations that took into account the most significant excited states, using a coupled-reaction channel approach. A very good agreement with the experimental data was achieved. \textbf{Conclusions:} The present results are the first demonstration of the investigation transfer reactions using detectors directly installed in the ring. This provides an important proof-of-principle for prospective studies with far-from-stability radioactive beams in the future.

   nucl-exPRC(2024)·3 citations
2. 02*

   $t$+$t$ cluster states in ${}^6$He

   W. H. Ma🇨🇳 · D. Y. Tao · B. Zhou🇨🇳 · J. S. Wang · Y. G. Ma🇨🇳 · D. Q. Fang🇨🇳 · W. B. He🇨🇳 · Y. Y. Yang🇹🇼 · J. B. Ma🇨🇳 · S. L. Jin · P. Ma🇨🇳 · J. X. Li🇨🇳 and 12 other authors

   The study of $t$+$t$ cluster states in ${}^6$He provides valuable insights into exotic nuclear structures and the behavior of fermionic cluster systems. This study shows rich cluster resonant state structures above the threshold, identified by experimental reconstruction and theoretical calculations. The excitation energy spectrum above the $t$+$t$ threshold in ${}^6$He is measured via the fragmentation excitation process during the breakup reaction of ${}^9$Li on a ${}^{208}$Pb target at an incident energy of 32.7 MeV/nucleon. The resonant states are reconstructed from the final state coincident particles $t$+$t$ using the invariant mass method, while the non-resonant background is estimated using the event mixing method. Two states of energy level peaks at $13.9\pm 0.3$ and $15.0\pm 0.3$ MeV are observed. Microscopic cluster model calculations exploring the $t+t$ resonant states in ${}^6\mathrm{He}$ yield theoretical energy spectra which are then compared with the current experimental results. The calculated reduced width amplitudes (RWA) of the $t+t$ channels further confirm the clustering structure of the identified $t+t$ resonant states.

   nucl-exnucl-th0 citations
3. 03*

   Mirror-skin thickness: a possible observable sensitive to the charge symmetry breaking energy density functional

   Tomoya Naito🇯🇵 · Yuto Hijikata🇯🇵 · Juzo Zenihiro🇯🇵 · Gianluca Colò🇮🇹 · Hiroyuki Sagawa🇯🇵

   We propose a new observable, named the mirror-skin thickness, in order to extract the strength of the charge symmetry breaking (CSB) term in an energy density functional (EDF). The mirror-skin thickness of $N=20$ isotones and $Z=20$ isotopes is studied by using Hartree-Fock-Bogoliubov (HFB) calculations with various Skyrme EDFs and adding CSB and charge independence breaking (CIB) terms. It is shown that the mirror-skin thickness is sensitive only to the CSB EDF, but hardly depends on either the isospin symmetric part of the nuclear EDF or the CIB term. Therefore, this observable can be used to extract the magnitude of the CSB term in the EDF quantitatively, either from experimental data or ab initio calculations. We have studied the accuracy in the mirror-skin thickness that is needed to extract sensible information. Our study may also help to understand the inconsistency between the strength of the phenomenological CSB and that extracted from ab initio calculations [Naito et al. Nuovo. Cim. C 47, 52 (2024)]. Among possible mirror pairs for experimental study, we propose the mirror-skin thickness between ${}^{42}\mathrm{Ca}$ and ${}^{42}\mathrm{Ti}$, which could be accessed in future experiments in RIBF and/or FRIB.

   ↳ nucl-thnucl-exEPJA(2025)·3 citations
4. 04*

   Electromagnetic emission from strongly interacting hadronic and partonic matter created in heavy-ion collisions

   Adrian William Romero Jorge🇩🇪 · Taesoo Song🇩🇪 · Qi Zhou🇨🇳 · Elena Bratkovskaya🇩🇪

   We investigate dilepton production in heavy-ion, proton-proton, and proton-nucleus collisions from low energies of 1 AGeV (SIS) to ultra-relativistic energies (LHC) using the Parton-Hadron-String Dynamics (PHSD) transport approach. PHSD is a microscopic, non-equilibrium approach that integrates hadronic and partonic degrees of freedom, providing a comprehensive description of relativistic heavy-ion collisions from initial nucleon-nucleon interactions to quark-gluon plasma (QGP) formation, hadronization, and final-state interactions. Key dilepton sources in PHSD include hadronic decays, bremsstrahlung, QGP radiation ($q+\bar{q}\to e^{+}{e}^{-}$, \ $q+\bar{q}\to g+e^{+}{e}^{-}$, \ $q+g\to q+e^{+}{e}^{-}$), primary Drell-Yan production, and semileptonic decays of correlated charm and bottom pairs. PHSD well describes dilepton data from HADES, STAR, and ALICE experiments. We examine in-medium effects, such as the vector meson spectral function broadening, and present the excitation function for the dilepton "excess" in the invariant mass range $0.4<M_{ee}<0.75$ GeV/c${}^2$. For the first time we report on the baryon chemical potential ${\mu }_B$-dependence of the QGP radiation calculated on a basis of the Dynamical-Quasi-Particle Model (DQPM) in PHSD. The influence of ${\mu }_B$ on the QGP yield grows at lower collision energies, where ${\mu }_B$ becomes large, however, its impact on the total dilepton spectra is small due to the lowering of the QGP volume with decreasing energy. The excitation function of QGP dileptons, is presented versus correlated charm, confirming that the QGP radiation overshines charm contributions at $\sqrt{s}\simeq 25-30$ GeV in central Au+Au collisions, providing access to thermal QGP dileptons at BES RHIC and FAIR.

   ↳ nucl-thnucl-exPRC(2025)·13 citations
5. 05*

   Geant4 and FLUKA Simulations of a Cyclotron Based 30 MeV Proton-Beryllium Reaction: Benchmarking and Optimization of Neutron Fields

   Egemen Gover · Doga Veske🇺🇸 · M.Bilge Demirkoz

   For studies where a reliable neutron source/beam is required and a nuclear reactor is not a viable option (considering their high neutron flux supply, which may not be suitable for research concerning low flux operations), alternative approaches may be sought. We present a comprehensive simulation analysis of 30 MeV proton induced ${}^9\mathrm{Be}\text{(p,n)}{}^9\mathrm{B}$ reaction, which can be utilized as an isotropic neutron source. This energy was chosen as it was the maximum allowed limit of protons supplied by IBA's Cyclone 30 XP proton cyclotron. Due to different underlying physics and transport mechanisms, when it comes to numerical calculations, slight variations in findings between different toolkits may occur. Hence it may require one to have a guide at hand to address the differences and interpret the data more accurately before conducting the actual experiment. In this work present the different numerical results of Geant4 and FLUKA. We conducted preliminary Monte Carlo runs to estimate the resulting neutron fluence and prompt gamma dose equivalents, while also assessing the degree of moderation achieved by different thicknesses of high density polyethylene. Furthermore, this work also presents an examplar modular irradiation station designed for target-moderator configurations, with the capability of generating thermal neutron fields.

   ↳ physics.ins-detnucl-ex0 citations
6. 06*

   Systematic optimization of resonance parameters in a transport approach

   Carl B. Rosenkvist🇩🇪 · Hannah Elfner🇩🇪

   This study optimizes resonance parameters responsible for strangeness production in the SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) transport model using a genetic algorithm. By fitting resonance parameters to experimental data on exclusive strangeness cross-sections at low energies, we significantly improve the model's accuracy, especially in pion-proton interactions. Our approach explores how machine learning tools can be used for precise resonance tuning in transport approaches.

   ↳ hep-phnucl-exnucl-thPRC(2025)·2 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.