Nuclear Theory·nucl-th

Tuesday·October 22, 2024

13 papers—8 primary·5 cross-listed

01
Regulator-independent equations of state for neutron stars generated from first principles
J. M. Alarcón🇪🇸 · E. Lope-Oter🇪🇸 · J. A. Oller🇪🇸
We study the equation of state (EoS) of a neutron star (NS) accounting for new advances. In the low energy density, $n \leq 0.1 n_{s}$ , with $n_{s}$ the saturation density, we use a new pure neutron matter EoS that is regulator independent and expressed directly in terms of experimental nucleon-nucleon scattering data. In the highest-density domain our EoS's are matched with pQCD to $O (α_{s}^{3})$ . First principles of causality, thermodynamic consistency and stability are invoked to transit between these two extreme density regimes. The EoS's are further constrained by the new measurements from PREX-II and CREX on the symmetry energy ( $S_{0}$ ) and its slope ( $L$ ). In addition, we also take into consideration the recent experimental measurements of masses and radii of different NSs and tidal deformabilities. A band of allowed EoS's is then obtained. Interestingly, the resulting values within the band for $S_{0}$ and $L$ are restricted with remarkably narrower intervals than the input values, with $32.9 \leq S_{0} \leq 39.5 MeV$ and $37.3 \leq L \leq 69.0 MeV$ at the 68\% CL. The band of EoS's constructed also allows possible phase transitions (PTs) for NS masses above 2.1~ $M_{⊙}$ at 68\% CL for $n > 2.5 n_{s}$ . We find both long and short coexistence regions during the PT, corresponding to first and second order PTs, respectively. We also generate the band of EoS's when excluding the astrophysical observables. This is of interest to test General Relativity and modified theories of gravity. Our band of EoS's for NSs can be also used to study other NS properties and dark matter capture in NS.
nucl-thastro-ph.HEhep-phPRD(2025)·10 citations
02
Pair momentum dependence of tilted source in heavy ion collisions
Yevheniia Khyzhniak🇺🇸 · Michael Annan Lisa🇺🇸
In non-central heavy-ion collisions, the particle-emitting source can be tilted away from the beam direction, an effect that becomes particularly significant at collision energies of a few GeV and lower. This phenomenon, manifest itself in many observables such as directed flow, polarization, and vorticity, is therefore important to investigate. In this paper, we study the consistency between the tilt extracted directly from the freeze-out distribution of pions and the tilt parameter obtained using the azimuthally sensitive femtoscopy (asHBT) method. Using the UrQMD model, we demonstrate a strong dependence of the tilt parameter extracted with asHBT on the momentum of the particle pair. Considering the experimental challenges in accessing low particle momenta - where the tilt parameter extracted with asHBT closely matches the tilt of the freeze-out distribution of pions - we propose an exponential extrapolation method to obtain the tilt of the entire freeze-out distribution. This approach aims to enhance the accuracy of experimental measurements of tilt in non-central heavy-ion collisions.
nucl-thhep-phnucl-exPRC(2025)·5 citations
03
Relativistic second-order spin hydrodynamics: A Kubo-type formulation for the quark-gluon plasma
Duan She🇨🇳 · Yi-Wei Qiu🇨🇳 · Defu Hou🇨🇳
Building upon Zubarev's nonequilibrium statistical operator formalism, we derive a relativistic canonical-like second-order spin hydrodynamics for two power-counting schemes. We obtain comprehensive second-order expressions for dissipative fluxes, including the shear stress tensor, bulk viscous pressure, charge-diffusion currents, rotational stress tensor, boost heat vector, and spin tensor-related dissipative flux. By introducing novel transport coefficients and expressing them in terms of equilibrium correlation functions, we establish new Kubo-type formulas for second-order transport. Our findings have significant implications for understanding the collective spin dynamics of strongly interacting matter and provide a robust theoretical basis for future experimental and theoretical studies.
nucl-thPRD(2025)·17 citations
04
Superheavy Magic Nuclei: Ground-State Properties, Bubble Structure and {\alpha}-Decay Chains
R. Sharma · A. Jain · M. Kumawat · J. K. Deegwal · Abdul Quddus · G. Saxena
A systematic investigation of superheavy nuclei in the isotopic chains of proton numbers Z=106, 114, 120, and 126 together with isotonic chains of neutron numbers N=162, 172, and 184 is presented in the theoretical framework of relativistic mean-field density functionals based on density-dependent meson-nucleon couplings. Ground-state properties, including binding energy, shape, deformation, density profile, and radius, are estimated to provide compelling evidence of magicity in these even-even nuclei, aligning with the concept of the 'island of stability'. The analysis reveals central depletion in the charge density, indicating a bubble-like structure, primarily attributed to the substantial repulsive Coulomb field and the influence of higher l-states. A thorough examination of potential decay modes, employing various semi-empirical formulas, is presented. The probable alpha-decay chains are evaluated, demonstrating excellent agreement with available experimental data
nucl-thNPA(2025)·2 citations
05
Test of $T$ -invariance in scattering of polarized protons on tensor-polarized deuterons at energies of the NICA SPD
Yu.N. Uzikov🇷🇺 · M.N. Platonova🇷🇺
The effect of violation of $T$ -invariance, provided that $P$ -parity is preserved, is given by the total cross section of the interaction of a vector-polarized particle with a tensor-polarized target. A formalism for calculating this effect developed previously and based on the spin-dependent Glauber theory of elastic $p d$ scattering is used here to calculate the effect under discussion in the range of collision energies corresponding to the invariant mass of the $pN$ system $s_{pN} = 5$ -- $30$ GeV. The spin-dependent amplitudes of elastic $pN$ scattering required for this calculation are taken from existing phenomenological models for $pN$ scattering in the energy region considered.
nucl-thhep-exhep-phnucl-exPhys.Part.Nucl.(2025)·2 citations
06
Shell quenching in nuclear charge radii based on Monte Carlo dropout Bayesian neural network
Zhen-Yan Xian · Yan Ya · Rong An
Charge radii can be generally used to encode information about various fine structures of finite nuclei. In this work, a constructed Bayesian neural network based on the Monte Carlo dropout approach is proposed to accurately describe the charge radii of nuclei with proton number $Z \geq 20$ and mass number $A \geq 40$ . More motivated underlying mechanisms are incorporated into this combined model in addition to the basic building blocks with the specific number of protons and neutrons, which naturally contain the pairing effect, the isospin effect, the shell closure effect associated with the Casten factor $P$ , the valence neutrons, the valence protons, the quadrupole deformation $β_{20}$ , the high order hexadecapole deformation $β_{40}$ , and the local shape staggering effect of $^{181, 183, 185}$ Hg. To avoid the distorted cases of the traditional Casten factor at the fully filled shells, the modified Casten factor $P^{*}$ is introduced into the input structure parameter sets. The standard root-mean-square deviation is reduced to $0.0084$ fm for the training data set and $0.0124$ fm for the validation data set with the modified Casten factor $P^{*}$ . Meanwhile, the shell closure effect of nuclear charge radii can be reproduced remarkably well. We have successfully demonstrated the ability of this constructed model to significantly increase the accuracy in predicting the nuclear charge radii.
nucl-thnucl-exPLB(2025)·6 citations
07
The nuclear symmetry energy and the neutron skin thickness in nuclei
G. F. Burgio · H. C. Das · I. Vidana (INFN Sezione di Catania)
We investigate possible correlations between the stiffness of the symmetry energy at saturation density, the so-called $L$ parameter, and the neutron skin thickness of $^{48}$ Ca and $^{208}$ Pb, for which the recent measurements from the CREX and PREX I+II experiments at the Thomas Jefferson Laboratory became available. We choose an ensemble of nucleonic equations of state (EoS) derived within microscopic (BHF, Variational, AFDMC) and phenomenological (Skyrme, RMF, DD-RMF) approaches. They are all compatible with the laboratory nuclear collisions data and with current observations of neutron stars (NS) mass and the tidal polarizability of a 1.4 $M_{⊙}$ NS, as deduced from the GW170817 event. We find some degree of correlation between the $L$ parameter and the neutron skin thickness whereas a much weaker correlation does exist with the tidal polarizability and the symmetry energy at saturation density. However, some EoS which are able to explain the CREX experimental data, are not compatible with the PREX I+II data, and viceversa. We confirm the results previously obtained with a different set of EoS models, and find a possible tension between the experimental data and the current understanding of the nuclear EoS.
nucl-thFront.Astron.Space Sci.(2024)·6 citations
08
Heavy Quarkonium-nuclear bound states within a generalized linear sigma model
Arpita Mondal🇮🇳 · Amruta Mishra🇮🇳
We estimate the binding energies of charmonium ( $J / ψ$ , $ψ (2 S)$ , $ψ (1 D)$ , $χ_{c 0}$ , $χ_{c 1}$ , $χ_{c 2}$ ) and bottomonium ( $Υ (1 S)$ , $Υ (2 S)$ , $Υ_{2} (1 D)$ , $χ_{b 0}$ , $χ_{b 1}$ , $χ_{b 2}$ ) states bound in various nuclei ( $^{4} He$ , $^{12} C$ , $^{16} O$ , $^{40} Ca$ , $^{90} Zr$ , and $^{208} Pb$ ) using the quarkonia-nuclei potentials obtained from their mass shifts in nuclear matter within the generalized linear sigma model. In the absence of light partons in heavy quarkonia, at the tree level, the medium modifications are driven by the gluon condensate, which is simulated within this model through a scalar dilaton field, $χ$ , by introducing broken scale invariance of QCD. Our study shows that charmonium states bind more deeply with the atomic nuclei as compared to bottomonium states, providing a better probe for nuclear medium effects. Such bound states' investigations are particularly interesting for the upcoming J-PARC-E29, $P ˉ ANDA$ @FAIR, and CEBAF@JLab experiments. The mass shifts of the heavy quarkonium states in hot isospin asymmetric nuclear matter are investigated and are observed to receive an appreciable medium modification. These medium effects are anticipated at FAIR@GSI, where such neutron-rich hot nuclear matter is expected to be produced.
nucl-thhep-ph1 citation

Affiliations

first authorsco-authorsvia INSPIRE