Nuclear Theory·nucl-th

Friday·July 25, 2025

15 papers—5 primary·10 cross-listed

01
[Submitted on 24 Jul 2025]
Impact of spin polarization on transport and thermodynamic coefficients
De-Xian Wei🇨🇳
This work investigates the influence of parton spin polarization on effective transport and thermodynamic coefficients in noncentral light- and heavy-ion collisions. To model this influence, I consider two sources of spin polarization: thermal vorticity, induced by angular momentum, and thermal shear, arising from local velocity gradients. Using a novel kinetic theory framework, one finds that transport and thermodynamic coefficients -- including the speed of sound squared $c_{s}^{2}$ , specific shear viscosity $η / s$ , specific bulk viscosity $ζ / s$ , and mean free path $λ$ -- are substantially modified by spin polarization effects. Among the two sources, thermal vorticity-induced spin polarization dominates the modifications to these coefficients. Moreover, both $c_{s}^{2}$ and $ζ / s$ exhibit a nonmonotonic dependence on the collision energy, and the associated scaling behaviors potentially serve as indicators of the critical phenomena of quantum chromodynamics.
Comments:
10 pages, 6 figures, publish version
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2507.18038 [pdf]
PRC(2025)·1 citation
02
[Submitted on 24 Jul 2025]
Re-examination of fusion hindrance in astrophysical $^{12}$ C+ $^{12}$ C and $^{12}$ C+ $^{13}$ C reactions
Kotaro Uzawa · Kouichi Hagino
To determine the energy dependence of fusion cross sections at extremely low energies is crucial for various astrophysical processes. In the previous study by Jiang et al. [Phys. Rev. C75, 015803 (2007)], it was concluded that fusion cross sections for the $^{12}$ C+ $^{12}$ C system rapidly drop off as the energy decreases. We here re-examine this hindrance phenomenon. While the previous study fitted the logarithmic slope $L (E)$ of fusion cross sections with a function of $L (E) = A + B / E^{n}$ and searched the optimum value of $A$ and $B$ with $n = 1.5$ , we refit the data with the same function for $L (E)$ but by releasing the restriction on $n$ . We find that the optimum values of $n$ significantly deviates from $n = 1.5$ , resulting in the absence of hindrance of fusion cross sections both in the $^{12}$ C+ $^{12}$ C and the $^{12}$ C+ $^{13}$ C systems.
Comments:
6 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
2507.18065 [pdf]
PRC(2025)·3 citations
03
[Submitted on 24 Jul 2025]
Proton-neutron pairing correlations in N=Z nuclei with Deformed Skyrme+pnBCS model
Xin Lian · C.L. Bai · H. Sagawa · H. Q. Zhang
We investigate the effects of neutron-neutron (nn), proton-proton (pp) and proton-neutron (pn) pairing correlations on the ground-states of $N = Z$ even-even $p f$ -shell nuclei by using an axially symmetric deformed Hartree-Fock (HF)+pnBardeen-Cooper-Schrieffer (BCS) model. We adopt a Skyrme energy density functional (EDF) SGII, together with contact volume- and surface-type pairing interactions, whose strengths are adjusted to reproduce empirical pairing gaps of each nucleus. It is shown that the strength of the IS pairing is correlated to the nuclear deformation: for oblate deformation with $- 0.3 < β_{2} < 0.0$ , a stronger IS pairing is required to reproduce the empirical pairing gap, while for prolate deformation a weaker one is enough. Among the eight $N = Z$ nuclei, we found that $^{64}$ Ge, $^{68}$ Se and $^{72}$ Kr show the dominance of isovector (IV) spin-singlet superfluidity, while lighter 5 nuclei $^{44}$ Ti, $^{48}$ Cr, $^{52}$ Fe, $^{56}$ Ni and $^{60}$ Zn exhibit the coexistence of IV spin-singlet and isoscalar (IS) spin-triplet superfluidities. We found also that the IS abnormal density always exhibits the oblate deformation, regardless of whether the normal density is prolate, spherical or oblate.
Comments:
9 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2507.18124 [pdf]
2 citations
04
[Submitted on 24 Jul 2025]
Investigating $^{238}$ U Deformation via Dilepton Production in Relativistic Heavy-Ion Collisions
Wen-Hao Zhou🇨🇳 · Lu-Meng Liu🇨🇳 · Che Ming Ko🇺🇸 · Kai-Jia Sun🇨🇳 · Jun Xu🇨🇳
Due to their weak coupling to the strongly interacting matter produced in relativistic heavy-ion collisions, dileptons serve as a sensitive probe of the initial geometry of the colliding nuclei. In this study, we investigate the influence of initial nuclear quadrupole deformation, characterized by the parameter $β_{2}$ , on dilepton production in $U + U$ collisions at $s_{N N} = 196$ GeV. The analysis is varried out using a modified multiphase transport model in which partonic interactions are described by the Nambu-Jona-Lasinio model. We observe a clear linear dependence of dilepton yields on $β_{2}^{2}$ in both the low-mass region (LMR, $< 1 G e V / c^{2}$ ) and intermediate-mass region (IMR, $1 - 3 G e V / c^{2}$ ) of the dilepton spectrum for the most central collisions. Also, dilepton production in the IMR region exhibits a stronger sensitivity to nuclear deformation than in the LMR, reflecting the dominance of earlier partonic processes in this mass range. These results suggest that precise measurements of dilepton yields in relativistic heavy-ion collisions can provide a viable means to determine the deformation parameter $β_{2}$ of $^{238}$ U.
Comments:
6 pages with 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2507.18189 [pdf]
PLB(2026)·0 citations
05
[Submitted on 24 Jul 2025]
Neutron Star Core-Crust Transition and Crustal Moment of Inertia: Systematic Implications of Higher-Order Symmetry Energy in the Nuclear Equation of State
W. M. Seif · A. S. Hashem
We investigate how higher-order symmetry-energy coefficients of the equation of state (EOS) describing $n p e μ$ core matter impact key neutron star (NS) properties at its crust inner edge, its moment of inertia and corresponding crustal fraction, threshold conditions for direct Urca process, adiabatic index, and related structure observables. Our analysis employs a comprehensive set of CDM3Y-IVF1 equations of state, derived from the M3Y-Paris nucleon-nucleon interaction within a non-relativistic Hartree-Fock framework, covering a wide range of nuclear matter stiffness, from soft ( $K_{0} = 150$ MeV) to extremely stiff (330 MeV) regimes. Our analysis reveals that the stiffer EOS characterized by higher isoscalar incompressibility ( $K_{0}$ ) and fourth-order symmetry-energy skewness ( $Q_{4}$ ) coefficients, coupled with diminished negative values of isoscalar $Q_{0}$ and $H_{0}$ , and isovector $K_{4}$ , $K_{τ 4}$ , $I_{2, 4}$ , and $G_{2}$ coefficients, systematically increase the estimated core-crust transition pressure, density, and charged-particle ( $p, e, μ$ ) fractions, and their threshold values for direct Urca process, as well as the total NS moment of inertia and its crustal fraction, and the central adiabatic index. Simultaneously, they yield less central fraction of $p$ , $e$ , and $μ$ , and reduced fractional crust thickness and moment of inertia for the maximum NS mass supported by a certain EOS. Conversely, enhanced values of the isoscalar kurtosis $I_{0}$ and $G_{0}$ symmetry coefficients, and of the higher-order $Q_{2}$ , $H_{2}$ , $K_{6}$ and $K_{τ 6}$ coefficients, combined with diminished negative contributions from $K_{2}$ and $K_{τ 2}$ , produce systematically opposite effects on the mentioned NS quantities, reversing their trends with $K_{0}$ .
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2507.18384 [pdf]
PRC(2025)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE

Impact of spin polarization on transport and thermodynamic coefficients

Re-examination of fusion hindrance in astrophysical 12C+12C and 12C+13C reactions

Proton-neutron pairing correlations in N=Z nuclei with Deformed Skyrme+pnBCS model

Investigating 238U Deformation via Dilepton Production in Relativistic Heavy-Ion Collisions

Neutron Star Core-Crust Transition and Crustal Moment of Inertia: Systematic Implications of Higher-Order Symmetry Energy in the Nuclear Equation of State

Affiliations

Re-examination of fusion hindrance in astrophysical $^{12}$ C+ $^{12}$ C and $^{12}$ C+ $^{13}$ C reactions

Investigating $^{238}$ U Deformation via Dilepton Production in Relativistic Heavy-Ion Collisions