Nuclear Theory·nucl-th

Tuesday·September 17, 2024

18 papers—9 primary·9 cross-listed

01
Multiple-models prediction for light neutron-rich isotopes cross section by $Q_{g}$ systematics in $^{40}$ Ar projectile fragmentation reactions
X. B. Wei · H. L. Wei · C. W. Ma · C. Y. Qiao · Y. F. Guo · J. Pu · K. X. Cheng · Y. T. Wang · Z. X. Wang · T. R. Zhou · D. Peng · S. T. Wang and 11 other authors
Precise predictions for nuclei near drip lines are crucial for experiments in new generation of rare isotope facilities. A multi-models investigation of the $Q_{g}$ systematics for fragments production cross sections, with $Q_{g}$ defined as the difference of mass excess (ME) between the projectile ( $Z_{p}, A_{p}$ ) and the fragment ( $Z_{f}, A_{f}$ ) nuclei $Q_{g} = M E (Z_{p}, A_{p}) - M E (Z_{f}, A_{f})$ , has been performed to verify the model prediction abilities for light neutron-rich isotopes in measured $^{40}$ Ar + $^{9}$ Be projectile fragmentation reactions from 57 $A$ MeV to 1 $A$ GeV. The models used are the FRACS parametrizations and the newly developed Bayesian neural networks (BNN) model. %method The results show that FRACS, BNN, and $Q_{g}$ extrapolations are generally consistent, except for fragments near the nuclear mass of the projectile. Additionally, both measured data and model extrapolations provide evidence for a shell closure at $N =$ 16 in fluorine and neon, as well as the disappearance of the traditional magic number $N =$ 20 in neon, sodium and magnesium.
nucl-thnucl-ex0 citations
02
Pion-nucleon scattering with decuplet contribution in heavy baryon SU(3) chiral perturbation theory
Jing Ou-Yang🇨🇳 · Bo-Lin Huang🇨🇳
We calculate the complete $T$ matrices with decuplet contributions for pion-nucleon scattering to order $O (ϵ^{3})$ in heavy baryon SU(3) chiral perturbation theory. The baryon mass in the chiral limit $M_{0}$ and the low-energy constants are determined by fitting to phase shifts of $π N$ , the experimental octet-baryon masses, and the value of $σ_{π N}$ simultaneously. By using these constants, we obtain the $K N$ $σ$ terms, $σ_{K N}^{(1)} = (375.07 \pm 33.02)$ MeV and $σ_{K N}^{(2)} = (275.32 \pm 32.24)$ MeV, with the errors being only statistical. An excellent description of the phase shifts is obtained for all partial waves. We also present results for scattering lengths and scattering volumes. In addition, the convergence of the approach is also discussed.
nucl-thhep-lathep-phnucl-exPRD(2024)·4 citations
03
Effect of Magnetic Fields on Urca Rates in Neutron Star Mergers
Pranjal Tambe🇮🇳 · Debarati Chatterjee🇮🇳 · Mark Alford🇺🇸 · Alexander Haber🇺🇸
Isospin-equilibrating weak processes, called ``Urca" processes, are of fundamental importance in astrophysical environments like (proto-)neutron stars, neutron star mergers, and supernovae. In these environments, matter can reach high temperatures of tens of MeVs and be subject to large magnetic fields. We thus investigate Urca rates at different temperatures and field strengths by performing the full temperature and magnetic-field dependent rate integrals for different equations of state. We find that the magnetic fields play an important role at temperatures of a few MeV, especially close to or below the direct Urca threshold, which is softened by the magnetic field. At higher temperatures, the effect of the magnetic fields can be overshadowed by the thermal effects. We observe that the magnetic field more strongly influences the neutron decay rates than the electron capture rates, leading to a shift in the flavor equilibrium.
nucl-thastro-ph.HEhep-phPRC(2025)·13 citations
04
Ab initio calculation of the $^{3}$ He $(α, γ)^{7}$ Be astrophysical S factor with chiral two- and three-nucleon forces
M.C. Atkinson · K. Kravvaris · S. Quaglioni · P. Navrátil
The $^{3}$ He $(α, γ)^{7}$ Be radiative capture reaction plays a key role in the creation of elements in stars as well as in the production of solar neutrinos, the observation of which is one of the main tools to study the properties of our sun. Since accurate experimental measurements of this fusion cross section at solar energies are difficult due to the strong Coulomb repulsion between the reactants, the onus falls on theory to provide a robust means for extrapolating from the region where experimental data is available down to the desired astrophysical regime. We present the first microscopic calculations of $^{3}$ He $(α, γ)^{7}$ Be with explicit inclusion of three-nucleon forces. Our prediction of the astrophysical $S$ factor qualitatively agrees with experimental data. We further incorporate experimental bound-state and scattering information in our calculation to arrive at a more quantitative description. This process reveals that our current model lacks sufficient repulsion in the $1/ 2^{+}$ channel of our model space to simultaneously reproduce elastic-scattering data. This deficit suggests that $^{3}$ He $(α, γ)^{7}$ Be probes aspects of the nuclear force that are not currently well-constrained.
nucl-thastro-ph.SRPLB(2025)·14 citations
05
Fuzzy logic for reconstructing arbitrary moments of multiplicity distributions
Anar Rustamov🇩🇪
The Identity Method is a statistical technique developed to reconstruct moments of multiplicity distributions of particles produced in high-energy nuclear collisions. The method leverages principles from fuzzy logic, allowing for a more nuanced representation of particle identification by assigning degrees of membership to different particle types based on detector signals. In this contribution, a new framework, based on a multivariate moment generation function, is developed that allows the derivation of the formulas used in the Identity Method in a more robust way. Moreover, within the introduced framework, the Identity Method is easily extended to cope with arbitrarily higher-order moments. The techniques developed here offer significant potential for improving the accuracy of multiplicity distribution analyses in high-energy nuclear collisions. While the primary focus of the work presented is on applications in high-energy particle and nuclear physics, it can also be applied in other areas where signal identification is probabilistic and data are noisy, such as in medical imaging, remote sensing, and various other fields of experimental science.
nucl-thhep-exhep-phnucl-exPRC(2024)·5 citations
06
Quantum-mechanical description of angular motion of fission fragments at scission
T. M. Shneidman (1) · A. Rahmatinejad (1) · G. G. Adamian (1) · N. V. Antonenko (1) ( (1) Joint Institute for Nuclear Research, Dubna, Russia)
The quantum-mechanical description of the collective angular motion in a system of two touching fission fragments is proposed. The main peculiarities of excitation spectrum and the structure of the wave functions are investigated. As found, the angular motion approximately corresponds to independent vibrations of fragments around the pole-to-pole configuration. The model allows us to explain the experimentally observed lack of correlation between the angular momenta of fission fragments. Additionally the correlation between angular momentum and fragment mass is primarily linked to the change of fragments deformation. The saw-tooth behavior of angular momentum distribution with respect to the fragment mass is well explained.
nucl-thPRC(2025)·6 citations
07
Multiple rescattering effects in the hard knockout reaction $^{2} \mbox H (p, 2p) n$
A.B. Larionov🇷🇺
The interaction of a proton with a deuteron is the simplest nuclear reaction. However, it allows the study of precursors of nuclear medium effects such as initial-state/final-state interactions (ISI/FSI). In case of hard proton knockout, the deviation of ISI/FSI from the 'standard' values may carry a signal of color transparency. In this regard, it is important to define the 'standard' as precisely as possible. This work continues previous studies within the framework of the Generalized Eikonal Approximation (GEA). The focus is on processes where the participating protons experience multiple soft rescattering on the spectator neutron. It is shown that correct treatment of deviations of the trajectories of outgoing protons from the longitudinal direction leads to a significant modification of partial amplitudes with soft rescattering of two outgoing protons and non-vanishing amplitudes with rescattering of incoming and outgoing protons. The new treatment of multiple rescattering is important in kinematics with a forward spectator neutron.
nucl-thhep-exhep-phnucl-exEPJA(2025)·1 citation
08
Ab initio calculations of anomalous seniority breaking in the $π g_{9/2}$ shell for the $N = 50$ isotones
Q. Yuan · B. S. Hu
We performed \textit{ab initio} valence-space in-medium similarity renormalization group (VS-IMSRG) calculations based on chiral two-nucleon and three-nucleon interactions to investigate the anomalous seniority breaking in the neutron number $N = 50$ isotones: $^{92}$ Mo, $^{94}$ Ru, $^{96}$ Pd, and $^{98}$ Cd. Our calculations well reproduced the measured low-lying spectra and electromagnetic $E 2$ transitions in these nuclei, supporting partial seniority conservation in the first $π g_{9/2}$ shell. Recent experiments have revealed that, compared to the symmetric patterns predicted under the conserved seniority symmetry, the $4_{1}^{+} \to 2_{1}^{+}$ $E 2$ transition strength in $^{94}$ Ru is significantly enhanced and that in $^{96}$ Pd is suppressed. In contrast, the $6_{1}^{+} \to 4_{1}^{+}$ and $8_{1}^{+} \to 6_{1}^{+}$ transitions exhibit the opposite trend. We found that this anomalous asymmetry is sensitive to subtle seniority breaking effects, providing a stringent test for state-of-the-art nucleon-nucleon interactions and nuclear models. We analyzed the anomalous asymmetry using VS-IMSRG calculations across various valence spaces. Our \textit{ab initio} results suggest that core excitations of both proton and neutron across the $Z = 50$ shell are ascribed to the observed anomalous seniority breaking in the $N = 50$ isotones.
nucl-thnucl-exPLB(2024)·9 citations
09
Lévy walk of pions in heavy-ion collisions
Dániel Kincses🇭🇺 · Márton Nagy🇭🇺 · Máté Csanád🇭🇺
The process of Lévy walk, i.e., movement patterns described by heavy-tailed random walks, plays a role in various phenomena, from chemical and microbiological systems through marine predators to climate change. Recent experiments have suggested that this phenomenon also appears in heavy-ion collisions. However, the theoretical interpretation supporting such findings is still debated. In high-energy collisions of heavy nuclei, the strongly interacting Quark Gluon Plasma is created, which, similarly to the early Universe, undergoes a rapid expansion and transition back to hadronic matter. In the subsequent expanding hadron gas, particles interact until kinetic freeze-out, when their momenta stop changing, and they freely transition toward the detectors. Measuring spatial freeze-out distributions is a crucial tool in understanding the dynamics of the created matter and the interactions among its constituents. In this paper, we introduce a three-dimensional analysis of the spatial freeze-out distribution of pions (the most abundant particles in such collisions). Utilising Monte-Carlo simulations of high-energy collisions, we show that the chain of processes ending in a final state pion has a step length distribution leading to Lévy-stable distributions. Subsequently, we show that simulated pion freeze-out distributions indeed exhibit heavy tails and can be described by a three-dimensional elliptically contoured symmetric Lévy-stable distribution.
nucl-thhep-phCommun.Phys.(2025)·17 citations
10
Predictions for photon-jet correlations at forward rapidities in heavy-ion collisions
Souvik Priyam Adhya🇵🇱 · Krzysztof Kutak🇵🇱 · Wieslaw Placzek🇵🇱 · Martin Rohrmoser🇵🇱 · Konrad Tywoniuk🇳🇴
In this work, we study for the first time jet-medium interactions in heavy-ion collisions with introduction of saturation and Sudakov effects with parameters tuned for upcoming forward calorimeter acceptances in experiments, in particular the ALICE FoCal detector. We focus on $γ +$ jet correlations by taking into account in-medium parton evolution using the BDIM equation that describes jet interactions with the quark-gluon plasma (QGP) combined with vacuum-like emissions (VLE). We systematically introduce the early time gluon saturation dynamics through the small- $x$ Improved Transverse Momentum Dependent factorization (ITMD). For our purpose, we use Monte Carlo programs KATIE and TMDICE to generate hard events and in-medium parton evolution, respectively. We present results of azimuthal correlations and nuclear modification ratios to gauge the impact of the gluon saturation effects at early time for the in-medium jet energy loss.
↳ hep-phhep-exnucl-thEPJC(2025)·3 citations
11
Optical model potentials for deuteron scattering off $^{24}$ Mg, $^{28}$ Si, $^{58}$ Ni, $^{90}$ Zr, $^{116}$ Sn, and $^{208}$ Pb at $\sim$ 100 MeV/nucleon
D. Patel · D.C. Cuong · K.B. Howard · U. Garg · Dao T. Khoa · H. Akimune · G.P.A. Berg · M. Fujiwara · M.N. Harakeh · M. Itoh · C. Iwamoto · T. Kawabata and 4 other authors
Angular distributions of the elastic and inelastic deuteron-nucleus scattering off $^{24}$ Mg, $^{28}$ Si, $^{58}$ Ni, $^{90}$ Zr, $^{116}$ Sn, and $^{208}$ Pb have been measured at a beam energy of 98 MeV/nucleon, with the goal of constraining the deuteron optical potential in this kinematical regime, and to extract the reduced transition probabilities for the ground-state transitions to low-lying excited states of these nuclei. Two potential models were used in the analysis of the measured $(d, d)$ and $(d, d^{'})$ data within the optical model and the distorted-wave Born approximation: the phenomenological optical model potential associated with the collective model of nuclear scattering, and the semi-microscopic double-folding model of the deuteron-nucleus potential based on a realistic density-dependent M3Y interaction. The deuteron optical potential and inelastic $(d, d^{'})$ scattering form factors were calculated using these two potential models, allowing for a direct comparison between the potential models as well as the validation of the deduced $E λ$ transition rates.
↳ nucl-exnucl-thPRC(2024)·0 citations
12
Resonance suppression during the hadronic stage from the FAIR to the intermediate RHIC energy regime
Amine Chabane🇩🇪 · Lisa Engel🇩🇪 · Tom Reichert🇩🇪 · Jan Steinheimer🇩🇪 · Marcus Bleicher🇩🇪
The energy and centrality dependence of the kaon resonance ratio $(K^{* 0} + \Bar K^{* 0}) / (K^{+} + K^{-})$ is explored in the RHIC-BES and CBM-FAIR energy regime. To this aim, the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model is employed to simulate reconstructable $K^{*}$ resonances in Au+Au and p+p collisions from $s_{NN} = 3 - 39$ GeV. We obtain a good description of the resonance yields and mean transverse momenta over the whole investigated energy range. The decrease of the $K^{*} / K$ ratio, with increasing centrality is in line with the available experimental data. We also observe the experimenatlly measured increase in $⟨ p_{T} ⟩$ with increasing centrality which is interpreted as a lower reconstruction probability of low- $p_{T}$ $K^{*}$ due to the $p_{T}$ dependent absorption of the decay daughter hadrons. We conclude that the observed suppression of reconstructable $K^{*}$ resonances provides a strong sign of an extended hadronic rescattering stage at all investigated energies. Its duration increases from peripheral to central reactions as expected. Following a method, suggested by the STAR experiment, the "duration" of the hadronic stage is extracted using the $K^{*} / K$ ratios at chemical and kinetic freeze-out. The resulting lifetimes are in good agreement with the experimental data, but much shorter than the actual lifetime of the hadronic phase in the transport simulation. This indicates that the experimental method to estimate the life time of the hadronic stage is too simplified.
↳ hep-phnucl-exnucl-thPRC(2025)·6 citations
13
Domain-wall Skyrmion phase of QCD in magnetic field: Gauge field dynamics
Yuki Amari🇯🇵 · Minoru Eto🇯🇵 · Muneto Nitta🇯🇵
The ground state of QCD in sufficiently strong magnetic field at finite baryon density is an inhomogeneous state consisting of an array of solitons, called the chiral soliton lattice (CSL). It is, however, replaced in a region with higher density and/or magnetic field by the so-called domain-wall Skyrmion(DWSk) phase where Skyrmions are created on top of the CSL. This was previously proposed within the Bogomol'nyi-Prasad-Sommerfield (BPS) approximation neglecting a gauge field dynamics and taking into account its effect by a flux quantization condition. In this paper, by taking into account dynamics of the gauge field, we show that the phase boundary between the CSL and DWSk phases beyond the BPS approximation is identical to the one obtained in the BPS approximation. We also find that domain-wall Skyrmions are electrically charged with the charge one as a result of the chiral anomaly.
↳ hep-phcond-mat.mes-hallnucl-thJHEP(2025)·13 citations
14
New insights into the analytic structure of correlation functions via kinetic theory
Robbe Brants🇧🇪
The way a relativistic system approaches fluid dynamical behaviour can be understood physically through the signals that will contribute to its linear response to perturbations. What these signals are is captured in the analytic structure of the retarded correlation function. The non-analyticities can be grouped into three types based on their dimension in the complex frequency plane. In this paper, we will use kinetic theory to find how we can calculate their corresponding signals. In the most general case of a system with particles that have a continuum of thermalization rates, we find that a non-analytic region appears. To calculate its signal, we introduce the non-analytic area density that describes the properties of this region, and we construct a method to calculate it. Further, to take into account the ambiguity present in signal analysis, following from manipulations of the non-analyticities, we will identify two specific choices called pictures with interesting analytic properties and compare in what scenarios each picture is most useful.
↳ hep-thhep-phnucl-thPRD(2024)·18 citations
15
N $^{3}$ LL + $O (α_{s}^{2})$ predictions of lepton-jet azimuthal angular distribution in deep-inelastic scattering
Shen Fang🇨🇳 · Mei-Sen Gao🇨🇳 · Hai Tao Li🇨🇳 · Ding Yu Shao🇨🇳
We present an analysis of lepton-jet azimuthal decorrelation in deep-inelastic scattering (DIS) at next-to-next-to-next-to-leading logarithmic (N $^{3}$ LL) accuracy, combined with fixed-order corrections at $O (α_{s}^{2})$ . In this study, jets are defined in the lab frame using the anti- $k_{T}$ clustering algorithm and the winner-take-all recombination scheme. The N $^{3}$ LL resummation results are derived from the transverse-momentum dependent factorization formula within the soft-collinear effective theory, while the $O (α_{s}^{2})$ fixed-order matching distribution is calculated using the {\tt NLOJET++} event generator. The azimuthal decorrelation between the jet and electron serves as a critical probe of the three-dimensional structure of the nucleon. Our numerical predictions provide a robust framework for precision studies of QCD and the nucleon's internal structure through jet observables in DIS. These results are particularly significant for analyses involving jets in HERA data and the forthcoming electron-ion collider experiments.
↳ hep-phhep-exnucl-exnucl-thJHEP(2025)·11 citations
16
Neutral pion to two-photons transition form factor revisited
M. Atif Sultan🇨🇳 · Jiayin Kang🇨🇳 · Adnan Bashir🇲🇽 · Lei Chang🇨🇳
Based upon a combined formalism of Schwinger-Dyson and Bethe-Salpeter equations in quantum chromodynamics (QCD), we propose a QCD kindred algebraic model for the dressed quark propagator, for the Bethe-Salpeter amplitude of the pion and the electromagnetic quark-photon interaction vertex. We then compute the $γ^{*} π^{0} γ$ transition form factor $G^{γ^{*} π^{0} γ} (Q^{2})$ for a wide range of photon momentum transfer squared $Q^{2}$ . The quark propagator is expanded out in its perturbative functional form but with dynamically generated dressed quark mass. It has complex conjugate pole singularities in the complex-momentum plane which is motivated by the solution of the quark gap equation with rainbow-ladder truncation of the infinite set of Schwinger-Dyson equations. This complex pole singularity structure of the quark propagator can be associated with a signal of confinement which prevents quarks to become stable asymptotic states. The Bethe-Salpeter amplitude is expressed without a spectral density function, which encapsulate its low and large momentum behaviour. The QCD evolution of the distribution amplitude is also incorporated into our model through the direct implementation of Efremov-Radyushkin-Brodsky-Lepage evolution equations. We include the effects of the quark anomalous magnetic moment in the description of the quark-photon vertex whose infrared enhancement is known to dictate hadronic properties. Once the QCD kindred model is constructed, we calculate the form factor $G^{γ^{*} π^{0} γ} (Q^{2})$ and find it consistent with direct QCD-based studies as well as most available experimental data. It slightly exceeds the conformal limit for large $Q^{2}$ which might be attributed to the scaling violations in QCD. The associated interaction radius and neutral pion decay width turn out to be compatible with experimental data.
↳ hep-phnucl-thPRD(2024)·6 citations
17
The Current State of the Controversy over Screening in Nuclear Reactions
Werner Däppen
A controversy about the possibility of dynamic effects in nuclear screening has been around for several decades. On the one hand, there is the claim that there are no dynamic effects, and that the classic Salpeter correction based on static Debye screening is all that is needed for astrophysical applications. The size of the correction is on the order of 5% in typical solar fusion reactions. On the other hand, numerical simulations have shown that there is a dynamical effect, which essentially cancels the Salpeter correction. The results of the numerical simulations were later independently confirmed. The astrophysical community, however, has so far largely ignored the possibility of dynamical screening. The present paper is meant to serve as a reminder of the controversy. Not only does the claim of an absence of a dynamical effect equally warrant an independent confirmation, but there is motivation for further investigation, such as the assessment of current laboratory experiments and a quantitative study of the dynamical effect in case it will turn out to be real.
↳ astro-ph.SRnucl-exnucl-thSolar Phys.(2024)·1 citation
18
Beth-Uhlenbeck equation for the thermodynamics of fluctuations in a generalised 2+1D Gross-Neveu model
Biplab Mahato🇵🇱 · David Blaschke🇩🇪 · Dietmar Ebert🇩🇪
We study a generalized version of the Gross-Neveu model in 2+1 dimensions. The model is inspired from Graphene, which shows a linear dispersion relation near the Dirac points. The phase structure and the thermodynamic properties in the mean field approximation have been studied before. Here, we go beyond the mean field level by deriving a Beth-Uhlenbeck equation for Gaussian fluctuations formulated in phase shift solutions, which we explore numerically, for the first time including their momentum dependence. We discuss the excitonic mass, fluctuation pressure, and phase shifts. The inclusion of momentum dependence in the phase shift shows a significant difference from the Lorentz-boosted version of the phase shift previously used in the literature. We find resurrection of the pseudoscalar bound states at large momentum above Mott temperature and show that the presence of Landau modes significantly contributes to the fluctuation pressure.
↳ cond-mat.mes-hallhep-phnucl-thPRD(2025)·2 citations

Affiliations

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