Nuclear Theory·nucl-th

Tuesday·August 18, 2026

20 papers—12 primary·8 cross-listed

01
Raubold-Lynch construction of the phase space in hypertriton three-body mesonic decay
Emile Meoto🇨🇲
A Monte Carlo construction is presented for the three-body mesonic decay phase space of the hypertriton. This is accomplished using the Raubold-Lynch sequential two-body decay algorithm. The method factorises this three-body decay into successive two-body decays through a virtual intermediate subsystem, whose invariant mass is sampled over the full kinematically allowed region. Exact relativistic two-body kinematics and Lorentz transformations are employed to construct complete four-momenta for all decay products. The construction is applied to both charged- and neutral-pion decay channels, yielding events that reproduce the Lorentz-invariant three-body phase-space measure. The resulting momentum spectra, pairwise momentum correlations, opening-angle distributions, and Dalitz plots furnish a complete kinematic characterisation of both decay modes. The neutral-pion channel exhibits a larger available three-body energy and correspondingly broader kinematic limits. The unweighted events generated provide a kinematic baseline that can subsequently be weighted event by event with a weak-decay matrix element, for computing decay rates and other observables. For the neutral-pion channel, where no experimental data currently exists, the Lorentz-invariant phase-space constitutes a useful baseline for predictions.
nucl-th0 citations
02
General Lindblad equation for quarkonium evolution in a quark-gluon plasma
Aoumeur Daddi Hammou · Jean-Paul Blaizot · Pol Bernard Gossiaux · Thierry Gousset
Accurate modelling and understanding of quarkonium production in ultrarelativistic heavy ion collisions requires a formalism that preserves the quantum properties of microscopic $Q ˉ Q$ systems while treating the interaction of such pairs with the quark-gluon plasma (QGP). The open quantum system approach has recently emerged as one of the most fruitful schemes to meet such requirements. However, the quantum master equations obtained so far in this context are derived assuming a strict ordering between the QGP temperature $T$ and the $Q ˉ Q$ energy gaps ( $Δ E$ ) of the quarkonia bound states. This limits their predictive power since, as the QGP expands and cools down, the system traverse all regimes between the quantum Brownian motion (QBM) regime for $T ≳ Δ E$ to the quantum optical (QO) regime for $Δ E ≳ T$ . In this paper, we derive and present a more general non-abelian quantum master equation of the Lindblad type, which does not suffer from these limitations and thus allows to faithfully describe the quantum evolution of the $Q Q ˉ$ pairs during the whole QGP-evolution. We also provide some illustration of the key quantities governing this equation.
nucl-thhep-phhep-thquant-ph1 citation
03
Extension of the dispersive optical model to improve the description of high-momentum components
R. A. Ramon · M. C. Atkinson · W. H. Dickhoff
An improved treatment of high-momentum components in nuclei is introduced in the framework of the dispersive optical model (DOM). The well-established feature that the peak of the spectral function appears at higher excitation energy in the $A$ -1 system with increasing momentum has so far not been successfully accounted for in the DOM. To achieve this feature, it is necessary to abandon the factorization of energy dependence and geometry of the DOM self-energy. The volume absorption below the Fermi energy has thus been represented by a decreasing radius at larger missing energy implying that a numerical treatment of the dispersion relations is necessitated. Earlier DOM results for $^{48}$ Ca are also improved with this approach, demonstrating that a small neutron skin can still be accompanied by protons having a larger high-momentum tail than neutrons.
nucl-th0 citations
04
Neutron Stars consistent Equations of State with Phase Transitions and their Impact in Heavy Ion Collision Observables
D. E. Lluis González🇩🇪 · J. Steinheimer🇩🇪 · M. Bleicher🇩🇪
We explore the impact of different equations of state (EoS) on heavy ion collision observables using a Chiral Mean Field (CMF) framework constrained by astrophysical and lattice QCD inputs. The investigated family of EoS simultaneously reproduce neutron stars with masses above two solar masses and exhibit a first order phase transition around two times the nuclear saturation density. This is achieved by varying the relative vector and scalar couplings of $Δ$ resonances with the scalar $σ$ and vector $ω$ fields with respect to nucleons. These EoS are compared to the QCD trace anomaly at finite temperature. We implement both, the default CMF EoS and the modified EoS featuring a phase transition into the UrQMD transport model to study the effects of the phase transition on a qualitative and quantitative level. In particular Au+Au collisions at beam energies of 0.5-3 GeV, the GSI/FAIR energy range of the HADES and CBM experiments, shows visible sensitivity on the EoS. Transverse momentum distributions for protons, the directed flow ( $v_{1}$ ) and its slope near mid-rapidity for $π^{+}$ as well as the $K^{+} / π^{+}$ ratio is analyzed. Clear differences emerge between the results obtained with the default CMF EoS, the modified EoS, and the cascade mode, particularly the slope of $v_{1}$ of the pions and in strangeness production. These findings demonstrate the sensitivity of heavy ion observables to the nuclear EoS and highlight potential experimental signatures of a phase transition.
nucl-th0 citations
05
Renormalization Group Analysis of Pairing Instabilities in Nuclear Fermi Liquids
Yang Xiao · Yixin Guo · Youngman Kim
A nuclear Fermi liquid exhibits competing pairing instabilities in different spin, isospin, and orbital channels. In a Fermi-surface renormalization group (RG) treatment, the channel that develops a pole first is determined not only by its tree-level attraction but also by its one-loop RG coefficient. We illustrate this mechanism in a minimal $S / P$ -wave model. A spherical Fermi surface establishes the reference competition between the lowest even- and odd-parity interactions. Axial deformation changes the relevant Fermi-surface integrals and lifts the degeneracy between longitudinal and transverse $P$ -wave components. In isospin-asymmetric matter, neutron--proton Fermi-momentum splitting restricts the simultaneous low-energy contribution of the two species and can terminate the $n p$ running at finite threshold scales. Our calculations are intended as controlled one-loop RG illustrations rather than as quantitative nuclear-matter calculations. We show how the Fermi-surface geometry and composition can change the ordering of competing pairing instabilities.
nucl-thcond-mat.quant-gascond-mat.str-elcond-mat.supr-con+10 citations
06
Deep-learning classification of physically admissible nuclear-matter equations of state
Ahmed Abuali🇺🇸 · Micheal Kahangirwe🇺🇸 · Francesco Di Clemente🇺🇸 · Vianney E Diaz-Barraza🇺🇸 · Jorge A Munoz🇺🇸 · Claudia Ratti🇺🇸
Thermodynamic stability and causality impose fundamental constraints on the equation of state (EoS) of nuclear matter. Verifying these constraints conventionally requires calculating quantities such as the specific heat, baryon-number susceptibility, and speed of sound, which can become computationally expensive when many candidate EoSs must be examined. We investigate whether the normalized pressure surface, $Q (T, μ_{B}) = P (T, μ_{B}) / T^{4}$ , alone contains sufficient information to determine the physical admissibility of an EoS. We develop a supervised convolutional neural network (CNN) that uses only this pressure representation to classify EoSs as physically admissible or inadmissible. The network is provided with training labels obtained from direct thermodynmaic stability and causality check and its does not get any information about the parameters of the underlying EoS framework. For EoSs generated within an Ising-mapping framework, the model achieves $97.65$ accuracy on unseen test data. Applied independently to EoSs from a distinct holographic framework, it achieves perfect classification of the test set. These results show that pressure surfaces contain geometric signatures of thermodynamic stability and causality violations that can be learned directly by a CNN. Because the classifier relies only on the pressure surface, it avoids evaluating higher-order thermodynamic observables during inference and is largely independent of the EoS-generation framework. When the pressure surface is supplied as a two-dimensional array, the machine-learning validation is approximately 20 times faster than direct validation. Our results establish a fast, framework-independent approach for identifying physically admissible EoSs directly from their pressure surfaces.
nucl-thcond-mat.stat-mechhep-thphysics.comp-ph0 citations
07
Origin and limits of intermediate-mass dilepton thermometry
Lipei Du🇺🇸
We identify the physical origin and limits of intermediate-mass dilepton thermometry in relativistic heavy-ion collisions. Using a controlled expanding-fireball framework with thermal dilepton rates, we show that the local inverse-slope parameter of the invariant-mass spectrum follows, to percent-level accuracy, the emission-weighted harmonic mean of the temperatures contributing to the spectrum. As the thermal-stage initial temperature increases, the temperatures sampled by the radiation shift upward with the overall thermal scale, causing their harmonic mean to track the initial temperature closely. This provides the physical basis for the strong inverse-slope--initial-temperature correlation, while the resulting mapping remains nonuniversal: changes that only rescale the amount of radiation leave it unchanged, whereas changes in the cooling history or source composition redistribute the radiation among different temperatures and modify the response. The mapping is nevertheless nearly linear over the temperature range studied here. Because different invariant-mass windows weight the emission history differently, source scenarios with the same inverse-slope parameter in $1 < M < 3 GeV$ develop different inverse slopes in harder mass windows. Intermediate-mass dilepton spectra therefore provide a quantitative but nonuniversal probe of the early thermal history, while measurements in multiple mass windows, when confronted with realistic calculations, can provide additional constraints on the thermal evolution and early electromagnetic source content.
nucl-thhep-ph0 citations
08
Scalable nuclear shell model calculations on noisy quantum computers
Durgesh Pandey🇮🇳 · Ankit Kumar Das🇮🇳 · P. Arumugam🇮🇳
The exact diagonalization of the nuclear shell model scales exponentially, leading to severe memory bottlenecks in classical high-performance computing (HPC). While hybrid quantum algorithms like the Variational Quantum Eigensolver (VQE) aim to overcome these limits, their deep quantum circuits and iterative feedback loops are susceptible to substantial noise inherent in the current Noisy Intermediate-Scale Quantum (NISQ) hardware. This noise renders several algorithms, such as the VQE, impractical for large-scale calculations despite sophisticated noise-mitigation techniques. As a pragmatic approach tolerant to these issues, we apply the Sample-based Quantum Diagonalization (SQD) framework to nuclear shell models for the first time. Using $^{38} Ar$ as a benchmark to confirm the numerical accuracy, we extend SQD to $^{32} Mg$ , solving a nuclear shell-model Hamiltonian whose underlying Hilbert space cannot be directly diagonalized using conventional classical methods in a given HPC system. We present a systematic comparison of SQD with standard variational quantum schemes and exact classical solvers. By leveraging NISQ hardware connected via the cloud to classical HPC clusters, the SQD-based scheme could outperform conventional supercomputers in memory scaling and total execution time, enabling more rigorous large-scale shell model calculations.
nucl-thquant-ph0 citations
09
Probing Vortex {\gamma} Photons via Nuclear Resonance Fluorescence
H. L. Chen · Y. F. Niu · F. Q. Chen
High-energy vortex {\gamma} photons offer unique prospects in nuclear physics, astrophysics, and strong-field physics, owing to their distinctive topological structure. Yet, their hallmark effects are erased in macroscopic targets, the only practical regime to date, when probed via the total transition probability of photoabsorption. Here we show that nuclear resonance fluorescence (NRF) circumvents this limitation. Using a Bessel-mode description, we demonstrate that for macroscopic targets, the target-averaged angular distribution of scattered photons retains a distinct dependence on the vortex polar angle, which emerges as the sole surviving vortex signature. Moreover, by scanning the vortex polar angle instead of the detector angle, we show that NRF can extract the angular momentum of nuclear excited states in a fixed-geometry setup. The vortex polar angle, a new degree of freedom in NRF, not only provides a direct quantitative diagnostic for vortex {\gamma} beams at the MeV energy scale, but also opens a new avenue for exploring orbital angular momentum-induced quantum phenomena in photonuclear physics.
nucl-th0 citations
10
Ab initio evidence for surface-dominated antiproton annihilation in $^{4} He$
Alireza Dehghani🇫🇷 · Guillaume Hupin🇫🇷 · Sofia Quaglioni🇺🇸 · Petr Navrátil🇨🇦
Low-energy antiproton beams at CERN/AD open the possibility of probing exotic nuclear structure through annihilation at the nuclear surface. The use of antiprotons as the probe for the nuclear surface is based on the assumption that the annihilation takes place at the periphery of the target. We test this idea for the lightest tightly bound nucleus, i.e., $^{4} He$ , using the ab initio no-core shell model combined with the resonating group method (NCSM/RGM), adapted to antiproton-nucleus dynamics. After validating our microscopic calculations against available atomic and scattering data, we use the microscopic annihilation density to examine where annihilation occurs inside the antiprotonic atom. We find that the annihilation peaks in the tail of the $^{4} He$ density, around $r \approx 2$ fm, and is strongly suppressed in the nuclear interior. Although this density is representation dependent, a similarity renormalization group (SRG) analysis of the NCSM/RGM Hamiltonian shows that the low-energy annihilation strength remains localized at large intercluster distances. These results support the phenomenological picture underlying antiprotonic-atom experiments: in a tightly bound system such as $^{4} He$ , antiproton annihilation is predominantly peripheral and is therefore sensitive to the nuclear-density tail.
nucl-th0 citations
11
Nuclear Drip Line and the Composition of Supernova Matter
S. Maity · S. Mallik
The nuclear drip line plays a crucial role in determining the composition of matter under extreme astrophysical conditions. In core-collapse supernovae and neutron-star crusts, matter is driven far from saturation density and nuclear stability; nuclei coexist with a sea of free neutrons, an effect that is present even at zero temperature in neutron-star crusts and becomes more pronounced in the hotter, neutron-rich supernova environment. This makes a careful treatment of drip-line physics essential for a realistic description of the equation of state and composition. In this work, the influence of the nuclear drip line on the baryonic composition of supernova matter is investigated within the framework of nuclear statistical equilibrium (NSE). The composition is evaluated in terms of free nucleons, light clusters, and heavy nuclei at finite temperature and global sub-saturation densities. The results indicate that, at low proton fractions and higher densities, the inclusion of nuclei beyond the drip line enhances the formation of extremely neutron-rich light clusters, leading to a significant reduction in the free-neutron density and the charge fraction of heavy nuclei. These findings demonstrate that drip-line physics has a significant impact on the composition of supernova matter and should be carefully incorporated in supernova modeling and nucleosynthesis studies.
nucl-thastro-ph.HEastro-ph.SRnucl-ex+1PRC(2026)·0 citations
12
Implementation of the Moments Method in TALYS: Sensitivity of $^{56, 57}$ Fe $(n, γ)$ observables to shell model nuclear level densities
Lucas Chouinard · Sofia Karampagia
The Moments Method (MM), a statistical spectroscopy framework built upon configuration interaction shell model Hamiltonians that enables shell model descriptions of nuclear level densities without requiring full diagonalization of the many body Hamiltonian, is implemented in the TALYS reaction code to investigate the sensitivity of Hauser-Feshbach calculations for the $^{56}$ Fe $(n, γ)^{57}$ Fe and $^{57}$ Fe $(n, γ)^{58}$ Fe reactions to the nuclear level density input. Spin- and parity-dependent MM level densities calculated in the pf shell are interfaced with TALYS and compared with the phenomenological and microscopic level density models available in the code. To construct TALYS-ready inputs, the MM level densities are extended to higher excitation energies using a back shifted Fermi gas continuation together with an experimentally constrained prescription for opposite-parity states. A sensitivity band for the MM calculations is estimated by varying a single parameter governing the statistical reconstruction of the level density. Neutron capture cross sections, Maxwellian averaged cross sections, and reaction rates are compared with evaluated ENDF/B-VIII.0 data and recommended KADoNiS and JINA-CEE values to assess the relative importance of the nuclear level density and $γ$ -ray strength function inputs. The calculations show that the observables are considerably more sensitive to the choice of $γ$ -ray strength function than to the MM level density variation considered here, while the MM-based results remain in good agreement with evaluated cross sections and recommended astrophysical reaction rates.
nucl-th0 citations

Affiliations

first authorsco-authorsvia INSPIRE