Nuclear Theory·nucl-th

Monday·January 22, 2024

9 papers—5 primary·4 cross-listed

01
Barrier penetration in a discrete-basis formalism
G.F. Bertsch · K. Hagino
The dynamics of a many-particle system are often modeled by mapping the Hamiltonian onto a Schrödinger equation. An alternative approach is to solve the Hamiltonian equations directly in a model space of many-body configurations. In a previous paper the numerical convergence of the two approaches was compared with a simplified treatment of the Hamiltonian representation. Here we extend the comparison to the nonorthogonal model spaces that would be obtained by the generator-coordinate method. With a suitable choice of the collective-variable grid, a configuration-interaction Hamiltonian can reproduce the Schrödinger dynamics very well. However, the method as implemented here requires that the barrier height is not much larger than the zero-point energy in the collective coordinates of the configurations.
nucl-thPRC(2024)·6 citations
02
Photoproduction of lepton pair in ultra-relativistic heavy-ion collisions
Kewei Yu🇨🇳 · Jiazhen Peng🇨🇳 · Shuang Li🇨🇳 · Kejun Wu🇨🇳 · Wei Xie🇨🇳 · Fei Sun🇨🇳
Dilepton production provides a unique probe of the strong electromagnetic field produced in heavy-ion collisions. To map out the behavior of its transverse momentum broadening, we present a theoretical model based on the equivalent photon approximation, and then we update it to make direct comparisons with the recent experimental measurements. We find that the model calculations can describe well, not only the average transverse momentum squared of $e^{+} e^{-}$ pairs in Au--Au collisions at $s_{NN} = 200$ GeV, but also the acoplanarity of $μ^{+} μ^{-}$ pairs in Pb--Pb collisions at $s_{NN} = 5.02$ TeV. Furthermore, the model predictions are also able to reproduce the measured dependencies of the pair mass and the transverse momentum squared.
nucl-thhep-phPRC(2024)·3 citations
03
Fine-tuning of the quasi-bound $K^{-} pp$ state
N.V. Shevchenko🇨🇿
Characteristics of the quasi-bound state in the $K^{-} pp$ system strongly depend on the model of antikaon-nucleon interaction and weakly - on the nucleon-nucleon potential. In the present paper, dynamically exact Faddeev-type calculations with coupled $K ˉ N N$ and $π Σ N$ were performed using different models of the $Σ N$ and $π N$ interactions to study the influence of these "less important" interaction on the three-body result. In addition, dynamically exact three-body Faddeev-type AGS calculations with three coupled particle channels $K ˉ N N - π Σ N - π Λ N$ were performed.
nucl-thFew Body Syst.(2024)·1 citation
04
Neutrino-Neutron Scattering Opacities in Supernova Matter
Gang Guo🇨🇳 · Gabriel Martínez-Pinedo🇩🇪 · Meng-Ru Wu🇹🇼
We compute the static density and spin structure factors in the long wavelength limit for pure neutron matter at subsaturation densities relevant to core-collapse supernovae within the Brueckner-Hartree-Fock (BHF) approach. The BHF results are reliable at high densities, extending beyond the validity of the virial expansion. Motivated by the similarities between the dilute neutron gas and a unitary gas, we propose a phenomenological approach to derive the static structures with finite momentum transfer as well as the dynamic ones with simple analytical expressions, based on the computed static structures in the long wavelength limit. We also compare the in-medium neutrino-neutron scattering cross sections using different structure factors. Our study emphasizes the importance of accurately computing the static structure factors theoretically and utilizing the full dynamic structure factors in core-collapse supernova simulations.
nucl-thastro-ph.SRPRC(2024)·2 citations
05
Unified neutron star equations of state calibrated to nuclear properties
Tuhin Malik🇵🇹 · Helena Pais🇵🇹 · Constança Providência🇵🇹
Recently, in Malik23, a dataset of several EoS for purely nucleonic stellar matter based on a non-linear RMF model prescription, and constrained to properties of nuclear matter, to state-of-the-art chiral effective field theory calculations for low-density neutron matter, and to astrophysical data, were proposed. In this work, twenty one unified neutron star EoS were chosen from that dataset, in such a way that a large range of values of the slope of the symmetry energy at saturation is covered. Several quantities are calculated and discussed, such as the the proton fraction and the direct Urca behavior, the density dependence of the speed of sound and the trace anomaly, the crust-core transition properties, the compatibility with astrophysical observations, and the neutron matter properties from $χ$ EFT calculations and pQCD constraints. We construct unified EoS, where the outer crust is given by the BSk22 functional, and the inner crust is calculated from a CLD approximation. The core is purely nucleonic, made of protons, neutrons, electrons and muons, under charge neutrality and in $β -$ equilibrium conditions. The correlation of the slope of the symmetry energy at saturation with the crust-core transition density and proton fraction is analysed, and equations that translate these relations are proposed. Moreover, the spectral representation for all the EOS according to the format proposed in Lindblom10 is given, which is a convenient representation to study quasi-periodic oscillations with realistic EOS. It is shown that several of these EoS have in the center of the most massive NS a speed of sound squared of the order of $≲ 0.5$ . Most of the EoS predict a maximum central density of the order of about 6 times the nuclear saturation density. Three of the EoS satisfy all of the constraints imposed. All these EoS will be made available in the CompOSE platform.
nucl-thAstron.Astrophys.(2024)·29 citations
06
Microscopic Encoding of Macroscopic Universality in QCD Chiral Phase Transition
Heng-Tong Ding🇨🇳 · Wei-Ping Huang🇨🇳 · Swagato Mukherjee · Peter Petreczky
We reveal that the universal scaling properties of the chiral phase transition in quantum chromodynamics (QCD) at the macroscale are, in fact, encoded within the microscopic energy levels of its fundamental constituents, the quarks. We introduce a novel relation between the cumulants of the chiral order parameter, i.e., the chiral condensate, and the correlations among the energy levels of quarks, i.e., the eigenspectra of the massless QCD Dirac operator. This relation elucidates how the fluctuations of the chiral condensate arise from the correlations within the infrared part of the energy spectra of quarks, and naturally leads to a generalization of the Banks-Casher relation for the cumulants of the chiral condensate. Then, through (2+1)-flavor lattice QCD calculations using HISQ action with varying light quark masses around the chiral phase transition temperature, we demonstrate that the correlations among the infrared part of the Dirac eigenvalue spectra exhibit same universal scaling behaviors as expected of the cumulants of the chiral condensate. We find that these universal scaling behaviors extend up to the physical values of the up and down quark masses.
↳ hep-latnucl-thPoS(2024)·0 citations
07
Energy-momentum tensor of the dilute (3+1)D Glasma
Andreas Ipp🇦🇹 · Markus Leuthner🇦🇹 · David I. Müller🇦🇹 · Sören Schlichting🇩🇪 · Kayran Schmidt🇦🇹 · Pragya Singh🇫🇮
We present a succinct formulation of the energy-momentum tensor of the Glasma characterizing the initial color fields in relativistic heavy-ion collisions in the Color Glass Condensate effective theory. We derive concise expressions for the (3+1)D dynamical evolution of symmetric nuclear collisions in the weak field approximation employing a generalized McLerran-Venugopalan model with non-trivial longitudinal correlations. Utilizing Monte Carlo integration, we calculate in unprecedented detail non-trivial rapidity profiles of early-time observables at RHIC and LHC energies, including transverse energy densities and eccentricities. For our setup with broken boost invariance, we carefully discuss the placement of the origin of the Milne frame and interpret the components of the energy-momentum tensor. We find longitudinal flow that deviates from standard Bjorken flow in the (3+1)D case and provide a geometric interpretation of this effect. Furthermore, we observe a universal shape in the flanks of the rapidity profiles regardless of collision energy and predict that limiting fragmentation should also hold at LHC energies.
↳ hep-phnucl-thPRD(2024)·19 citations
08
Unraveling collisional energy loss of a heavy quark in quark-gluon plasma
Jiazhen Peng🇨🇳 · Kewei Yu🇨🇳 · Shuang Li🇨🇳 · Wei Xiong🇨🇳 · Fei Sun🇨🇳 · Wei Xie🇨🇳
At leading order in QCD coupling constant, we compute the energy loss per traveling distance of a heavy quark $d E / d z$ from elastic scattering off thermal quarks and gluons at a temperature $T$ , including the thermal perturbative description of soft scatterings ( $- t < - t^{*}$ ) and a perturbative QCD-based calculation for hard collisions ( $- t > - t^{*}$ ). Within this soft-hard factorization model, we find that the full results of $d E / d z$ behaves a mild sensitivity to the intermediate cutoff $t^{*}$ , supporting the validity of the soft-hard approach within the temperature region of interest. We re-derive the analytic formula for $d E / d z$ in the high-energy approximation, $E_{1} ≫ m_{1}^{2} / T$ , where $E_{1}$ is the injected heavy quark energy and $m_{1}$ is its mass. It is realized that the soft logarithmic contribution, $d E / d z \propto l n (- t^{*} / m_{D}^{2})$ , arises from the $t$ -channel scattering off thermal partons, while the hard logarithmic term, $d E / d z \propto l n [E_{1} T / (- t^{*})]$ , stems from the $t$ -channel scattering off thermal partons, and the one $d E / d z \propto l n (E_{1} T / m_{1}^{2})$ comes from the $s$ - and $u$ -channel scattering off gluons. The sum of these contributions cancels the $t^{*}$ -dependence as observed in the full result. The mass hierarchy is observed $d E / d z (c ha r m) > d E / d z (b o tt o m)$ . Our full results are crucial for a better description of heavy quark transport in QCD medium, in particular at low and moderate energy. We also calculate the energy loss by imposing the Einstein's relationship. The related results appear to be systematically larger than that without imposing the Einstein's relationship.
↳ hep-phnucl-thPRD(2024)·11 citations
09
Using Bayesian Inference to Distinguish Neutrino Flavor Conversion Scenarios via a Prospective Supernova Neutrino Signal
Sajad Abbar🇩🇪 · Maria Cristina Volpe🇫🇷
The upcoming galactic core-collapse supernova is expected to produce a considerable number of neutrino events within terrestrial detectors. By using Bayesian inference techniques, we address the feasibility of distinguishing among various neutrino flavor conversion scenarios in the supernova environment, using such a neutrino signal. In addition to the conventional MSW, we explore several more sophisticated flavor conversion scenarios, such as spectral swapping, fast flavor conversions, flavor equipartition caused by non-standard neutrino interactions, magnetically-induced flavor equilibration, and flavor equilibrium resulting from slow flavor conversions. Our analysis demonstrates that with a sufficiently large number of neutrino events during the supernova accretion phase (exceeding several hundreds), there exists a good probability of distinguishing among feasible neutrino flavor conversion scenarios in the supernova environment.
↳ astro-ph.HEhep-phnucl-thPRD(2025)·12 citations

Affiliations

first authorsco-authorsvia INSPIRE