Nuclear Theory·nucl-th

Tuesday·March 10, 2026

25 papers—17 primary·8 cross-listed

18
[Submitted on 6 Mar 2026] (cross-list from astro-ph.HE)
Thermalization of Neutrinos in a Neutron Star Merger Simulation
Mark G. Alford🇺🇸 · Liam Brodie🇺🇸 · Francois Foucart🇺🇸 · Alexander Haber🇺🇸
We study the neutrino distributions that arise in a simulation of a neutron star merger that uses a Monte Carlo (MC) neutrino transport scheme. In a snapshot taken 1 ms after merger, we calculate relevant observables to test when neutrinos behave like a thermalized gas, and when a free-streaming picture is more appropriate. We find that in hot, dense regions where neutrino-matter interactions are frequent, MC neutrino and antineutrino distributions are consistent with thermalized neutrinos. In moderately warm regions, where neither approximation is expected to hold, we find significant departures from the predictions of the thermalized-neutrino approximation, particularly for the (anti)neutrino average opacity and net rate of absorption per baryon, even when average energies appear approximately thermal. At lower temperatures, MC results approach the free-streaming limit. Our results demonstrate that energy-averaged agreement with thermalized-neutrino assumptions does not guarantee accurate weak interaction rates. Non-equilibrium aspects of the neutrino distribution are therefore crucial for neutrino-mediated microphysics such as composition evolution in the early post-merger phase.
Comments:
v1: 14 pages and 8 figures. Code to generate and plot data: https://gitlab.com/liambrodie/neutrino-thermalization
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2603.06788 [pdf]
PRD(2026)·4 citations
19
[Submitted on 6 Mar 2026] (cross-list from astro-ph.HE)
Enhanced Neutrino Cooling from Parity-Doubled Nucleons in Neutron Star Cooling Simulations
Rodrigo Negreiros🇺🇸 · Liam Brodie🇺🇸 · Jan Steinheimer🇩🇪 · Veronica Dexheimer🇺🇸 · Robert D. Pisarski🇺🇸
Although restoration of chiral symmetry is predicted by quantum chromodynamics to take place at high baryon density, most modeling of neutron star interiors disregards a chiral phase transition. We model neutron star cores with a parity doublet model, which allows for dynamical chiral symmetry restoration and predicts the appearance of the parity partners of nucleons and hyperons at large densities, as well as deconfined quark matter. We study the thermal evolution of neutron stars, focusing for the first time on the impact of Urca processes involving the parity partners in neutron star cooling simulations. We find that Urca processes for the parity partners of the nucleons significantly affect the thermal evolution of massive stars and allow for improved agreement with observed surface temperature and ages.
Comments:
v1: 12 pages and 5 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2603.06789 [pdf]
5 citations
20
[Submitted on 8 Mar 2026] (cross-list from hep-ph)
Schwinger effect in QCD and nuclear physics
Hidetoshi Taya🇯🇵
We provide a pedagogical review of the Schwinger effect, i.e., the non-perturbative production of particle and anti-particle pairs from the vacuum by strong fields, as well as related strong-field phenomena. Beginning with an overview of the Schwinger effect in quantum electrodynamics, we discuss its extensions to quantum chromodynamics and its applications in nuclear physics, including high- $Z$ nuclei, string breaking, relativistic heavy-ion collisions, and the chiral anomaly.
Comments:
26 pages, 3 figures; a contribution to the Encyclopedia of Nuclear Physics
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th); Plasma Physics (physics.plasm-ph)
arXiv:
2603.07847 [pdf]
1 citation
21
[Submitted on 9 Mar 2026] (cross-list from hep-ph)
Physics-Informed Global Extraction of the Universal Small- $x$ Dipole Amplitude
Si-Wei Dai🇨🇳 · Fu-Peng Li🇨🇳 · Long-Gang Pang🇨🇳 · Guang-You Qin🇨🇳 · Shu-Yi Wei🇨🇳 · Han-Zhong Zhang🇨🇳 · Wenbin Zhao🇨🇳
We extract the universal small- $x$ dipole scattering amplitude $N (r, x_{B})$ from a global analysis based on a physics-informed neural network (PINN), without imposing a priori MV-type parametrization of the initial condition. The network provides a smooth and differentiable surrogate for $N (r, x_{B})$ , whose rapidity dependence is constrained by the collinearly improved Balitsky--Kovchegov evolution equation, while its functional form is simultaneously constrained by Deep Inelastic Scattering (DIS) data for the reduced total and charm cross sections, exclusive $J / ψ$ photoproduction measurements, and a positivity requirement for the momentum-space dipole amplitude. The resulting single universal amplitude consistently describes all fitted observables within a unified framework, alleviating the long-standing tension between total and charm channels encountered in conventional small- $x$ fits based on rigid parametric ansätze. Within the fitted kinematic domain, the best extracted PINN solution yields a smooth, non-negative momentum-space dipole over the full transverse-momentum range examined. Our results provide a robust and well-behaved input for Color Glass Condensate phenomenology across a broad class of high-energy processes.
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2603.08008 [pdf]
7 citations
22
[Submitted on 9 Mar 2026] (cross-list from hep-ph)
Heavy mesons with dynamical gluon on the light front
Jiatong Wu🇨🇳 · Hengfei Zhao🇨🇳 · Kaiyu Fu🇨🇳 · Zhi Hu🇨🇳 · Xingbo Zhao · James P. Vary🇨🇳
We investigate the structure of charmonium, bottomonium, and $B_{c}$ meson systems within the Basis Light-Front Quantization (BLFQ) approach, including both the quark-antiquark ( $∣ q q ˉ ⟩$ ) and quark-antiquark-gluon ( $∣ q q ˉ g ⟩$ ) Fock sectors. Our input light-front Hamiltonian incorporates a confining potential inspired by light-front holography, as well as the quark-gluon interaction from Quantum Chromodynamics. By adjusting model parameters to reproduce the mass spectra for low-lying states, we obtain the light-front wave functions for the heavy meson states. Based on these wave functions, we calculate electromagnetic form factors, decay constants, parton distribution amplitudes (PDAs), and parton distribution functions (PDFs) of the quarks and gluons in the heavy mesons. Our results for the charge radii and decay constants reasonably agree with experimental data and other theoretical approaches. The PDAs are consistent with the predictions from the earlier BLFQ calculations with an effective one-gluon exchange interaction. Furthermore, we present the first predictions within the BLFQ framework for the gluon PDFs in heavy mesons based on the light-front wave function in the $∣ q q ˉ g ⟩$ sector.
Comments:
20 pages, 70 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2603.08114 [pdf]
2 citations
23
[Submitted on 9 Mar 2026] (cross-list from astro-ph.SR)
s-process nucleosynthesis in low-mass AGB stars by the $^{13}$ C( $α$ ,n) $^{16}$ O neutron source
Inma Domínguez · Carlos Abia · Maurizio Busso · Oscar Straniero · Sara Palmerini
In this review we outline our knowledge on slow neutron captures, concentrating on its main part occurring during the final stages of stellar evolution for low or intermediate-mass stars when they evolve during the Asymptotic Giant Branch, or AGB, stars. We focus our attention on how, in this field, studies passed from a first era of inquiries based on nuclear systematics, to numerical nucleosynthesis computations performed in stellar codes. We then discuss how these last were forced, by observational constraints, to almost abandon, for the synthesis of nuclei between Sr and Pb, the rather naturally activated Ne22 neutron source (operating efficiently at T > 30 keV, and producing a neutron density N_n > 5 10^8 cm^-3). This implied considering the alternative reaction 13C(alpha,n)16O, that can be activated locally after each of the TDU. The mentioned crucial reaction occurs at T< 8 keV, in the time intervals separating two subsequent thermal pulses (TP). The layers where 13C(alpha,n)16O operates are characterized by a radiative equilibrium and their low temperature also yields low values for the neutron density (N_n < 10^7 cm^-3).
Comments:
19 pages, 8 figures, accepted for publication in EJP
Subjects:
Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
2603.08140 [pdf]
EPJA(2026)·1 citation
24
[Submitted on 9 Mar 2026] (cross-list from hep-ph)
Connecting baryon light-front wave functions to quasi-transverse-momentum-dependent correlators in lattice QCD
S. Rodini🇮🇹 · A. Schiavi🇮🇹 · B. Pasquini🇮🇹
Within light-front quantization, hadrons can be represented on a Fock-space basis of configurations of elementary partons. The coefficients of the expansion are called light-front wave functions (LFWFs), and encode all the dynamical degrees of freedom. We show how to extract the LFWFs of baryons, such as the proton, from equal-time correlators suitable for Lattice QCD simulations. Using an operator product expansion, we prove the factorization of the relevant correlator in the three-quark color-singlet LFWF, a residual lattice factor, and a soft factor that systematically subtracts the additional divergences arising from the factorization. We verify up to next-to-leading order the independent renormalizability of the LFWF, and we derive the evolution equations that govern its scale dependence.
Comments:
17 pages, 9 figures, consistent with published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2603.08405 [pdf]
PRD(2026)·0 citations
25
[Submitted on 9 Mar 2026] (cross-list from hep-ph)
Radiative corrections to the nucleon isovector $g_{V}$ and $g_{A}$
Oleksandr Tomalak🇨🇳 · Yi-Bo Yang🇨🇳
Electroweak, QCD, and QED radiative corrections to the nucleon low-energy coupling constants $g_{V}$ and $g_{A}$ are enhanced by large perturbative logarithms between the electroweak and hadronic scale, as well as between the hadronic scale and the low-energy MeV scale. Additionally, higher-order pion-mass splitting corrections to the nucleon axial-vector charge might be large. By consistently incorporating these effects, we provide an updated relation between the lattice-QCD and physical $g_{A}$ , finding a total radiative correction of $3.5 (2.1) %$ ( $5.6 (0.7) %$ ). This leads to an expected lattice-QCD result of $g_{A}^{QCD} = 1.265 (26)$ ( $g_{A}^{QCD} = 1.240 (9)$ ) when based on a combination of lattice-QCD and data-driven (or only data-driven) inputs, respectively. Future phenomenological, chiral perturbation theory, and lattice-QCD studies can improve both the central value and the uncertainty of this estimate.
Comments:
11 pages, 2 figures, version published in Universe, footnote 1 added, new sentence in footnote 3, corrected last equation in footnote 5, minor text changes
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2603.08596 [pdf]
Universe(2026)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE