Nuclear Theory·nucl-th

Tuesday·May 7, 2024

14 papers—10 primary·4 cross-listed

01
[Submitted on 4 May 2024]
External magnetic field induced paramagnetic squeezing effect in heavy-ion collisions at the LHC
Ze-Fang Jiang🇨🇳 · Zi-Han Zhang🇨🇳 · Xue-Fei Yuan🇨🇳 · Ben-Wei Zhang🇨🇳
In non-central heavy-ion collisions, the quark-gluon plasma (QGP) encounters the most intense magnetic field ever produced in nature, with a strength of approximately 10 $^{19 - 20}$ Gauss. Recent lattice-QCD calculations reveal that the QGP exhibits paramagnetic properties at high temperatures. When an external strong magnetic field is applied, it generates an anisotropic squeezing force density that competes with pressure gradients resulting from the purely QGP geometric expansion. In this study, we employ (3+1)-dimensional ideal hydrodynamics simulations to estimate the paramagnetic squeezing effect of this force density on the anisotropic expansion of QGP in non-central Pb+Pb collisions at the Large Hadron Collider (LHC). We consider both up-to-date magnetic susceptibility and various magnetic field profiles in this work. We find that the impact of rapidly decaying magnetic fields is insignificant, while enduring magnetic fields produce a strong force density that diminishes the momentum anisotropy of the QGP by up to 10% at the intial stage, leaving a visible imprint on the elliptic flow $v_{2}$ of final charged particles. Our results provide insights into the interplay between magnetic fields and the dynamics of QGP expansion in non-central heavy-ion collisions.
Comments:
11 pages, 8 figures, published in Phys. Rev. C 110, 014902 (2024)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2405.02610 [pdf]
PRC(2024)·7 citations
02
[Submitted on 4 May 2024]
Wobbling motion in triaxial nuclei
Stefan Frauendorf
The experimental evidence for the collective wobbling motion of triaxial nuclei is reviewed. The classification into transverse and longitudinal in the presence of quasiparticle excitations is discussed. The description by means of the quasiparticle+triaxial rotor model is discussed in detail. The structure of the states is analyzed using the spin-coherent-state and spin-squeezed-state representations of the reduced density matrices of the total and particle angular momenta, which distill the corresponding classical precessional motions. Various approximate solutions of the quasiparticle+triaxial rotor model are evaluated. The microscopic studies of wobbling in the small-amplitude random phase approximation are discussed. Selected studies of wobbling by means of the triaxial projected shell model are presented, which focus on how this microscopic approach removes certain deficiencies of the semi-microscopic quasiparticle+triaxial rotor model.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2405.02747 [pdf]
4 citations
03
[Submitted on 4 May 2024]
A Bayesian mixture model approach to quantifying the empirical nuclear saturation point
C. Drischler · P. G. Giuliani · S. Bezoui · J. Piekarewicz · F. Viens
The equation of state (EOS) in the limit of infinite symmetric nuclear matter exhibits an equilibrium density, $n_{0} \approx 0.16 fm^{- 3}$ , at which the pressure vanishes and the energy per particle attains its minimum, $E_{0} \approx - 16 MeV$ . Although not directly measurable, the saturation point $(n_{0}, E_{0})$ can be extrapolated by density functional theory (DFT), providing tight constraints for microscopic interactions derived from chiral effective field theory (EFT). However, when considering several DFT predictions for $(n_{0}, E_{0})$ from Skyrme and Relativistic Mean Field models together, a discrepancy between these model classes emerges at high confidence levels that each model prediction's uncertainty cannot explain. How can we leverage these DFT constraints to rigorously benchmark saturation properties of chiral interactions? To address this question, we present a Bayesian mixture model that combines multiple DFT predictions for $(n_{0}, E_{0})$ using an efficient conjugate prior approach. The inferred posterior for the saturation point's mean and covariance matrix follows a Normal-inverse-Wishart class, resulting in posterior predictives in the form of correlated, bivariate $t$ -distributions. The DFT uncertainty reports are then used to mix these posteriors using an ordinary Monte Carlo approach. At the 95\% credibility level, we estimate $n_{0} \approx 0.157 \pm 0.010 fm^{- 3}$ and $E_{0} \approx - 15.97 \pm 0.40 MeV$ for the marginal (univariate) $t$ -distributions. Combined with chiral EFT calculations of the pure neutron matter EOS, we obtain bivariate normal distributions for the symmetry energy and its slope parameter at $n_{0}$ : $S_{v} \approx 32.0 \pm 1.1 MeV$ and $L \approx 52.6 \pm 8.1 MeV$ (95\%), respectively. Our Bayesian framework is publicly available, so practitioners can readily use and extend our results.
Comments:
close to the published version; extended analysis and minor changes; 31 pages, 14 figures, 5 tables
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex); Data Analysis, Statistics and Probability (physics.data-an)
arXiv:
2405.02748 [pdf]
PRC(2024)·26 citations
04
[Submitted on 5 May 2024]
Bayesian uncertainty quantification for synthesizing superheavy elements
Yueping Fang · Zepeng Gao · Yinu Zhang · Zehong Liao · Yu Yang · Jun Su · Long Zhu
To improve the theoretical prediction power for synthesizing superheavy elements beyond Og, a Bayesian uncertainty quantification method is employed to evaluate the uncertainty of the calculated evaporation residue cross sections (ERCS) for the first time. The key parameters of the dinuclear system (DNS) model, such as the diffusion parameter $a$ , the damping factor $E_{d}$ , and the level-density parameter ratio $a_{f} / a_{n}$ are systematically constrained by the Bayesian analysis of recent ERCS data. One intriguing behavior is shown that the optimal incident energies (OIE) corresponding to the largest ERCS weakly depend on the fission process. We also find that these parameters are strongly correlated and the uncertainty propagation considering the parameters independently is not reasonable. The 2 $σ$ confidence level of posterior distributions for $a = 0.58 6_{- 0.002}^{+ 0.002}$ fm, $E_{d} = 25.6 5_{- 3.41}^{+ 3.43}$ MeV, and $a_{f} / a_{n} = 1.08 1_{- 0.021}^{+ 0.021}$ are obtained. Furthermore, the confidence levels of the ERCS and OIE for synthesizing Z = 119 via the reactions( $^{54} Cr +^{243} Am$ ), ( $^{50} Ti +^{249} Bk$ ), and ( $^{51} V +^{248} Cm$ ) are predicted. This work sets the stage for future analyses to explore the OIE and reaction systems for the synthesis of superheavy elements.
Comments:
7 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2405.02839 [pdf]
PLB(2024)·8 citations
05
[Submitted on 5 May 2024]
Charge-changing cross section and interaction cross sections for 4 $\leq$ Z $\leq$ 9 isotopes
M. Imran · Z. Hasan · A. A. Usmani · Z. A. Khan
The root-mean-square proton and neutron radii for $^{7, 9 - 12, 14}$ \rm Be, $^{10 - 15, 17}$ \rm B, $^{12 - 19}$ \rm C, $^{14, 15, 17 - 22}$ \rm N, $^{16, 18 - 24}$ \rm O, and $^{18 - 21, 23 - 26}$ \rm F isotopes are deduced from a systematic analysis of experimental charge-changing and interaction cross sections in the framework of Glauber model. The calculations involve descriptions of nuclei based on Slater determinants using harmonic oscillator single-particle wave functions. The extracted proton and neutron radii have been examined in the light of some important features such as neutron skin thickness/halo-like structure/subshell closure observed in exotic isotopes.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2405.02926 [pdf]
PRC(2024)·7 citations
06
[Submitted on 5 May 2024]
Extended NJL model for baryonic matter and quark matter
Cheng-Jun Xia🇨🇳
By considering baryons as clusters of three quarks, we extend the Nambu-Jona-Lasinio (NJL) model to describe baryonic matter, quark matter, and their transitions in a unified manner, where the Dirac sea and spontaneous chiral symmetry breaking are considered. In particular, a density-dependent structural function $α_{S}$ is introduced to modulate the four(six)-point interaction strengths to reproduce the baryon masses in vacuum and medium. Vector interactions are considered with the exchange of $ω$ and $ρ$ mesons, where the density-dependent coupling constants are fixed by reproducing nuclear matter properties as well as the $Λ$ -hyperon potential depth in nuclear medium. As density increases, quarks will emerge as quasi-free particles and coexist with baryons. This phase is interpreted as quarkyonic matter, where quarks are restricted to the lowest energy states in the presence of baryons, i.e., quarks are still confined. Similar to the treatment of $α$ clustering in nuclear medium, a Pauli blocking term is added to baryon masses so that baryons eventually become unbound in the presence of a quark Fermi Sea. Then at large enough densities baryons vanish and a Mott transition takes place, we consider such a transition as deconfinement phase transition. Depending on the strengths of Pauli blocking term and quark-vector meson couplings, both first-order and continues phase transitions are observed for quarkyonic, chiral, and deconfinement phase transitions. The corresponding compact star structures are then investigated and confronted with various astrophysical constraints.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2405.02946 [pdf]
PRD(2024)·14 citations
07
[Submitted on 6 May 2024]
Thermodynamic stability in relativistic viscous and spin hydrodynamics
Xiang Ren🇨🇳 · Chen Yang🇨🇳 · Dong-Lin Wang🇨🇳 · Shi Pu🇨🇳
We have applied thermodynamic stability analysis to derive the stability and causality conditions for conventional relativistic viscous hydrodynamics and spin hydrodynamics. We obtain the thermodynamic stability conditions for second-order relativistic hydrodynamics with shear and bulk viscous tensors, finding them identical to those derived from linear mode analysis. We then derive the thermodynamic stability conditions for minimal causal extended second-order spin hydrodynamics in canonical form, both with and without viscous tensors. Without viscous tensors, the constraints from thermodynamic stability exactly match those from linear mode analysis. In the presence of viscous tensors, the thermodynamic stability imposes more stringent constraints than those obtained from linear mode analysis. Our results suggest that conditions derived from thermodynamic stability analysis can guarantee both causality and stability in linear mode analysis.
Comments:
30 pages; published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
2405.03105 [pdf]
PRD(2024)·26 citations
08
[Submitted on 6 May 2024]
Magnetic dipole transition in proton-deuteron radiative capture at BBN energies within potential model
Nguyen Le Anh · Dao Nhut Anh · Do Huy Tho · Nguyen Huu Nha
The $p d$ radiative capture reaction plays a vital role in Big Bang nucleosynthesis and stellar proton-proton chain. The study of the low-energy reaction is challenging in both experiments and theories. Using the framework of potential model, we analyze $p d$ radiative capture below 1 MeV for both electric dipole ( $E 1$ ) and magnetic dipole ( $M 1$ ) transitions. The obtained astrophysical $S$ factors agree well with recent results, especially at energies relevant to sensitive deuterium abundance. The calculated reaction rate shows good agreement, with less than a 5\% difference compared to recent works. The extrapolated value for $S (0)$ including both transitions is determined to be $0.211 \pm 0.016$ eV b. A comparison with experimental data using the $χ^{2}$ test reveals the sensitivity of the $M 1$ cross section at low energies to the scattering potential depth.
Comments:
17 pages, 6 figures, 2 tables, accepted for publication in Physica Scripta
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2405.03210 [pdf]
Phys.Scripta(2024)·1 citation
09
[Submitted on 6 May 2024]
Finite size effect on gluon dissociation of J/psi in relativistic heavy ion collisions
Jingjing Wang🇨🇳 · Baoyi Chen🇨🇳 · Yunpeng Liu🇨🇳
Thermal quantities, including the the entropy density and gluon spectrum, of quark matter within a box that is finite in the longitudinal direction are calculated using a bag model. Under the assumption of entropy conservation, the corresponding gluon dissociation rate of J/psi is studied. It reaches a maximum at a certain longitudinal size L_m, below which the suppression is weak even if the temperature becomes higher than that without the finite size effect, and above which the dissociation rate approaches to the thermodynamic limit gradually with increasing longitudinal size of the fireball.
Comments:
8 pages, 4 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2405.03583 [pdf]
Chin.Phys.Lett.(2024)·2 citations
10
[Submitted on 6 May 2024]
Entanglement in selected Binary Tree States: Dicke/Total spin states, particle number projected BCS states
Denis Lacroix🇫🇷
Binary Tree States (BTS) are states whose decomposition on a quantum register basis formed by a set of qubits can be made sequentially. Such states sometimes appear naturally in many-body systems treated in Fock space when a global symmetry is imposed, like the total spin or particle number symmetries. Examples are the Dicke states, the eigenstates of the total spin for a set of particles having individual spin $1/2$ , or states obtained by projecting a BCS states onto particle number, also called projected BCS in small superfluid systems. Starting from a BTS state described on the set of $n$ qubits or orbitals, the entanglement entropy of any subset of $k$ qubits is analyzed. Specifically, a practical method is developed to access the $k$ qubits/particles von Neumann entanglement entropy of the subsystem of interest. Properties of these entropies are discussed, including scaling properties, upper bounds, or how these entropies correlate with fluctuations. Illustrations are given for the Dicke state and the projected BCS states.
Comments:
10 pages, 4 figures, any comment/remarks welcome
Subjects:
Nuclear Theory (nucl-th); Superconductivity (cond-mat.supr-con); Quantum Physics (quant-ph)
arXiv:
2405.03647 [pdf]
PRC(2024)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE