Nuclear Theory·nucl-th

Wednesday·May 27, 2026

12 papers—6 primary·6 cross-listed

01
CNN-Based Online Trigger for QGP Event Selection
Olga Soloveva🇩🇪 · Artemiy Belousov🇩🇪 · Ivan Kisel🇩🇪 · Elena Bratkovskaya🇩🇪
Modern high-rate experiments require rare physics signatures to be identified in real time from continuous streams of reconstructed events under stringent data-throughput and storage constraints. We present a convolutional-neural-network-based trigger concept for selecting events associated with quark-gluon plasma (QGP) formation. Events are encoded as compact multidimensional histograms of reconstructed particle content, including particle species, momentum magnitude, and angular information. The method is first evaluated within the Parton-Hadron-String Dynamics (PHSD) framework, where microscopic QGP-related labels are available. As an independent validation, the same event representation and network architecture are applied to Ultra-relativistic Quantum Molecular Dynamics (UrQMD) simulations, providing a distinct description of the collision dynamics. Cross-checks between PHSD and UrQMD are used to assess the stability of the learned response against generator-dependent effects and to quantify model-transfer robustness. For realistic deployment, a lightweight C++ inference package, ANN4FLES, is employed at the physics-analysis stage after tracking and topology reconstruction. For Au+Au collisions at 30 AGeV, the classification accuracy decreases from 95.1% on generator-level PHSD events to 83.7% after full reconstruction, while retaining practical separation power for online event selection. SHAP-based interpretability analysis is used to identify the dominant particle-species contributions to the network decision.
nucl-th0 citations
02
Spin-Dependent Nucleon-Nucleus Interactions Constrained by Neutron Observables and Their Impact on Near-Barrier Proton Fusion
Kyoungsu Heo · Myung-Ki Cheoun · Kouichi Hagino
We investigate the role of spin-dependent nucleon-nucleus interactions in nuclear reactions. To this end, we use neutron spin observables to constrain the dominant central spin-spin form factors and then apply the corresponding like-channel interactions to near-barrier fusion in the $p +^{93}$ Nb system. The interactions are constructed within a folding framework based on a finite-range effective nucleon-nucleon force and organized in terms of radial form factors associated with their spin-spin, tensor, and spin-orbit components. Neutron spin observables in the $n +^{27}$ Al, $n +^{59}$ Co, and $n +^{93}$ Nb target systems are analyzed within a distorted-wave Born approximation (DWBA) framework to constrain the sign and normalization in the central spin-spin parts of the radial form factors and to examine the assembled operator conventions. The calculation reproduces the observed sign systematics of the neutron spin observables for the three targets, indicating that the essential spin-dependent structure is properly incorporated. The unlike-channel (neutron-proton) interaction constrained by neutron scattering is then reconstructed for the corresponding like-channel (proton-proton) interaction and applied to a coupled-channels description of near-barrier fusion for the $p +^{93}$ Nb system. The resultant spin-dependent interactions lead only to a weak modification of the effective barrier and change the fusion cross section by about $0.01$ - $0.03%$ in the present calculation. These results show that the corresponding real spin-dependent correction in the like-channel is strongly suppressed in near-barrier fusion in $p +^{93} Nb$ . The present work thus connects the neutron-scattering constraints on the operator conventions with the fusion calculation in the proton channel, and quantifies the magnitude of the corresponding real spin-dependent correction in near-barrier fusion.
nucl-th0 citations
03
Cumulants of mean transverse momentum and elliptic flow in the hydrodynamic model of heavy-ion collisions
Tribhuban Parida🇵🇱 · Piotr Bożek🇵🇱
Higher order cumulants between the mean transverse momentum and elliptic flow are calculated in a relativistic viscous hydrodynamic model of relativistic heavy-ion collisions. The results of the hydrodynamic simulations are compared with calculations using event-by-event predictors of the final collective observables constructed from the initial state entropy distribution. The predictors describes quantitatively centrality dependence of the higher cumulants considered in the paper. We derive a quantitative relations between the cumulants of the mean transverse momentum and different moments of the harmonic flow. The hydrodynamic simulations satisfy those relation very well. Those relations could be used to test experimentally the collective origin of the observed correlations between the mean transverse momentum and harmonic flow.
nucl-thhep-exhep-phnucl-ex1 citation
04
Sensitivity of Heavy-Quark Dipolar Flow to its Initial Spatial Distributions in Cu+Au Collisions
Ankit Kumar Panda · Tribhuban Parida
We investigate charm-quark dynamics in asymmetric Cu+Au collisions at top RHIC energy using a Langevin approach embedded in a realistic hydrodynamic background. The intrinsic asymmetry of the colliding nuclei leads to a spatially lopsided initial energy-density profile, which generates a dipolar flow structure in the transverse plane even at midrapidity. As charm quarks propagate through this medium, they acquire a finite directed flow, $v_{1}$ . We find that the $p_{T}$ -integrated heavy-quark $v_{1}$ is approximately an order of magnitude larger than that of charged hadrons. In addition, the $p_{T}$ -differential $v_{1}$ exhibits strong sensitivity to the initial spatial distribution of heavy quarks, emphasizing the importance of pre-equilibrium dynamics in determining final-state anisotropies. Beyond geometric effects, $v_{1}$ also provides direct sensitivity to medium interactions through the temperature-dependent drag coefficient. Its pronounced dependence on this transport input indicates that precision measurements of heavy-flavor directed flow could place meaningful constraints on heavy-quark transport coefficients, thereby improving Langevin-based descriptions and predictive power for heavy-flavor observables in heavy-ion collisions.
nucl-thhep-exhep-phnucl-ex0 citations
05
Azimuthal asymmetry in exclusive quasi-elastic neutrino-nucleus interactions
Marco Vanderpoorten🇧🇪 · Ashish Kumar Jha🇧🇪 · Mathias El Baz🇨🇭 · Kajetan Niewczas🇧🇪 · Federico Sanchez🇨🇭 · Natalie Jachowicz🇧🇪
In neutrino oscillation experiments, exclusive measurements of neutrino-nucleus interactions play a critical role, by providing the theoretical and experimental input needed for a reliable estimation of the neutrino energy. In this paper, we derive the general form of the azimuthal angle distribution for quasi-elastic scattering, focusing on a dependency that has been routinely overlooked. We demonstrate that the outgoing nucleon exhibits a preference for emission outside the lepton scattering plane, with an asymmetric azimuthal distribution. In the context of neutrino-nucleus scattering, we argue that this asymmetry is caused by parity violation in the weak interaction. Furthermore, we show that in cross section calculations the asymmetry is sensitive to nuclear modeling choices and to the shell structure of the initial nucleus, thus providing a novel source of information for energy reconstruction in neutrino experiments. We study the experimental feasibility of observing this effect by applying a realistic momentum detection threshold and an intranuclear cascade. We estimate that the asymmetry is observable with $O$ ( $1 0^{4}$ ) events at the 99% confidence level for neutrino interactions on $^{12}$ C, suggesting that the effect is within reach of the current generation of neutrino detectors.
nucl-thhep-ph0 citations
06
Nuclear structure within the relativistic mean field approach including chiral symmetry and quark confinement effects
M. Chamseddine🇫🇷 · J.-P. Ebran🇫🇷 · E. Khan🇫🇷 · B. K. Pradhan🇫🇷 · J. Margueron🇺🇸 · H. Hansen🇫🇷 · G. Chanfray🇫🇷
The relativistic mean field approach, within a theoretical framework known as the chiral confining model incorporating chiral symmetry breaking and quark confinement effects, is applied for the first time to finite nuclei. Model parameters are calibrated through a Bayesian approach using nuclear empirical properties and doubly magic nuclei. The model provides a satisfactory description of binding energies and charge radii for medium and heavy nuclei, while larger discrepancies are observed in light nuclei. This behavior is linked to the constrained form of the chiral potential, which reduces flexibility away from saturation density. Charge radii are reproduced with very good accuracy, although density profiles remain slightly more diffuse than experimental ones. The extension to open-shell nuclei with a separable Gogny pairing interaction reveals enhanced pairing correlations associated with the large Dirac effective mass, reduced spin-orbit splittings, and increased single-particle level density around the Fermi surface. Finally, departures from the linear sigma model potential motivated by the Nambu-Jona-Lasinio framework are explored. Allowing additional flexibility in the chiral potential improves the description of light nuclei and reduces the Dirac mass, which in turn suppresses the anomalous pairing. These results highlight the sensitivity of finite nuclei properties to the structure of the chiral potential and the associated single-particle spectrum.
nucl-th1 citation
07
Nuclear Physics of Binary Neutron Star Mergers
Armen Sedrakian🇵🇱
Binary neutron star mergers provide a unique laboratory for studying matter under conditions that cannot be reproduced in terrestrial experiments. They probe dense matter at supranuclear density, finite temperature, rapid rotation, strong gravity, and extreme neutron excess, while producing observable signals in gravitational waves, electromagnetic radiation, and, in principle, neutrinos. This review focuses on the nuclear physics of binary neutron star mergers. We discuss the dense-matter equation of state (EoS), the inspiral and merger dynamics, the structure and lifetime of the post-merger remnant, transport and dissipative processes, weak interactions and neutrino transport, and the production of heavy elements through $r$ -process nucleosynthesis. Particular emphasis is placed on the connection between microscopic physics and multimessenger observables, including tidal deformability, post-merger gravitational-wave spectra, kilonova light curves, short gamma-ray bursts, and afterglows. We also review how observations of events such as GW170817, together with neutron star mass and radius measurements, laboratory nuclear experiments, and theoretical many-body calculations, constrain the EoS and the composition of dense matter. The goal is to summarize the current understanding of how nuclear physics controls the dynamics and observable signatures of binary neutron star mergers, and to identify the open questions that future multimessenger observations and improved nuclear theory will address.
↳ astro-ph.HEastro-ph.SRnucl-th0 citations
08
Muon-Catalyzed Nuclear Fusion: Physical Mechanism, Bottleneck Breakthroughs, and an Engineering Pathway
Xiong Yin🇨🇳 · Wei Kou🇨🇳 · Xurong Chen🇨🇳
Muon-catalyzed nuclear fusion (\mucf) replaces atomic electrons with negative muons, compressing atomic orbitals by about two orders of magnitude and enabling deuterium--tritium (D--T) fusion under near-room-temperature conditions. This paper reviews the physical principles of \mucf{} and formulates its essential dynamics as a four-step cycle: muonic-atom formation, muon transfer, resonant \dtmu{} molecular formation, and D--T fusion with muon release and recycling. A kinetic model is used to quantify the number of catalysis cycles per muon and the corresponding energy gain. We focus on the central limitation of catalytic efficiency, namely the alpha-sticking effect, and discuss possible breakthrough routes including nuclear-spin and muon dual polarization, in-flight muon-catalyzed fusion, and heavy-ion-driven magneto-inertial fusion. Within the idealized assumptions of the present model, a four-dimensional synergistic scheme combining dual polarization, high-density confinement, electric-field-assisted muon recovery, and resonant enhancement may increase the number of catalysis cycles per muon from the present experimental record of about 150 to more than 500, potentially enabling an energy gain $Q>2$. On this basis, we propose a conceptual fusion--fission fuel-breeding hybrid reactor, denoted as \mucf-FBR, which exploits the 14.1-MeV neutron yield of \mucf{} to breed ${}^{239}\mathrm{Pu}$ from a ${}^{238}\mathrm{U}$ blanket in a decoupled fusion--fission operating mode. This concept may offer advantages in engineering robustness, radiation-damage tolerance, and natural-uranium utilization.
↳ hep-phnucl-exnucl-thphysics.acc-ph0 citations
09
Isospin-breaking effects on the threshold cusp structures in $Λ N$ - $Σ N$ scattering
Katsuyoshi Sone · Tetsuo Hyodo
We discuss the isospin-breaking effects on threshold cusp structures in multichannel scattering near two-body thresholds. In hadronic systems with isospin symmetry, two or more nearly degenerate thresholds can appear, and their small splitting due to isospin breaking can generate multiple cusp structures in a narrow energy region. In this paper, using the $K$ -matrix representation, we derive a general expression for the scattering amplitude near the thresholds and show that the cusp structures can be classified by the signs of the slopes of the cross section above and below threshold. We also show that additional restrictions appear in two- or three-channel systems and in the Flatté amplitude. For three-channel scattering with two nearby thresholds, we clarify how the two cusp structures are related when the threshold splitting is small and how they merge into a single cusp in the degenerate limit. Finally, we discuss the cusp structures in the $Λ p$ elastic cross section in the coupled $Λ N$ - $Σ N$ system with charge $Q = + 1$ . We show that, when isospin breaking is small, the two cusp structures are constrained by isospin symmetry. We also perform quantitative calculations using both simplified examples and realistic input based on N $^{2}$ LO chiral effective field theory, and find that isospin breaking can significantly modify the relative sharpness of the cusps and may even change the cusp type itself.
↳ hep-phnucl-th0 citations
10
From supernovae to neutron stars: crust formation time
Yudai Suwa (U. Tokyo & YITP)🇯🇵 · Ken'ichiro Nakazato (Kyushu U.)🇯🇵
A neutron star is born as a hot, lepton-rich protoneutron star (PNS) and cools via neutrino emission, eventually allowing heavy ions in the outer layers to crystallize into a solid crust. We develop a simple analytic estimate for the onset time of this crust formation during the late, post-convective PNS cooling phase. Using a diffusion-based neutrino luminosity and the resulting entropy evolution together with an approximately isentropic interior structure, we obtain the time-dependent density and temperature at the neutrinosphere. We then impose the Coulomb crystallization condition for heavy nuclei, expressed through the Coulomb coupling parameter, and determine when the neutrinosphere temperature first falls below the crystallization threshold evaluated at the neutrinosphere density. This procedure yields closed expressions for the entropy at crystallization and the corresponding crust-formation time, with explicit dependence on the PNS mass and radius, an effective diffusion/cooling normalization, and composition parameters such as the ionic charge $Z$ and heavy-nuclei mass fraction. For canonical microphysics, we find that the first solid phase typically appears at $t_{crust} \sim 100$ - $500 s$ . These closed-form scalings provide a useful late-time analytic benchmark for the onset of crust formation and clarify its dependence on PNS and composition parameters.
↳ astro-ph.HEnucl-thPubl.Astron.Soc.Jap.(2026)·0 citations
11
Experimental and theoretical studies of hyperfine structures in $^{21}$ Na
Junho Won · Jeongsu Ha · Deuk Soon Ahn · Sunghoon Ahn · Vivek Chavan · Anastasiia Chekhovska · Gyoungmo Gu · Kevin Insik Hahn · Seongjin Heo · Jangyong Huh · Dahee Kim · Do Gyun Kim and 29 other authors
We measured the hyperfine structure constants, $A (3 s^{2} S_{1/2})$ and $A (3 p^{2} P_{1/2})$ , of the neutron-deficient isotope $^{21} Na$ using CLaSsy, a setup dedicated to collinear laser spectroscopy at RAON. The hyperfine structure constants of $^{21} Na$ were measured to be $103.6 (10)_{stat} (9)_{syst}$ MHz for $A (3 p^{2} P_{1/2})$ and $954.9 (11)_{stat} (25)_{syst}$ MHz for $A (3 s^{2} S_{1/2})$ . A systematic comparison with the state-of-the-art ab-initio relativistic coupled cluster calculations shows the role of higher-order correlation effects such as triple excitations in $^{21}$ Na. Furthermore, the measurement demonstrates a capability of the CLaSsy setup to conduct collinear laser spectroscopy experiments with a radioactive beam.
↳ physics.atom-phnucl-exnucl-th1 citation
12
Temperature-resolved sensitivities of $^{56} Ni$ production to helium-burning reactions in pair-instability supernovae
Hiroki Kawashimo · Nobuya Nishimura · Yudai Suwa
We propose a temperature-resolved Monte Carlo (MC) approach to identify the temperature regimes in which low-energy helium-burning reaction rates most strongly affect nucleosynthesis in very massive stars that undergo pair-instability supernovae (PISNe). By performing MC simulations of PISNe, we quantify how temperature-dependent variations in key helium-burning reaction rates, i.e., the triple- $α$ and $^{12} C (α, γ)^{16} O$ rates, influence $^{56} Ni$ synthesis. Thousands of stellar evolution calculations using $MESA$ reveal that both the $^{12} C (α, γ)^{16} O$ and triple- $α$ reactions exhibit their strongest sensitivity at $T ≃ 2.5 \times 1 0^{8} K$ , but with opposite correlation signs. We show that this temperature corresponds to the regime in which the ratio of the sampled rate multipliers is most clearly imprinted on the pre-carbon-burning C/O composition. This demonstrates that PISN nucleosynthesis can probe helium-burning reaction rates in specific low-temperature regimes.
↳ astro-ph.SRastro-ph.HEnucl-th0 citations

Affiliations

first authorsco-authorsvia INSPIRE