Nuclear Theory·nucl-th

Wednesday·July 13, 2022

8 papers—6 primary·2 cross-listed

01
Neutrinoless $β β$ -decay nuclear matrix elements from two-neutrino $β β$ -decay data
Lotta Jokiniemi🇪🇸 · Beatriz Romeo🇪🇸 · Pablo Soriano🇪🇸 · Javier Menéndez🇪🇸
We study two-neutrino ( $2 ν β β$ ) and neutrinoless double- $β$ ( $0 ν β β$ ) decays in the nuclear shell model and proton-neutron quasiparticle random-phase approximation (pnQRPA) frameworks. Calculating the decay half-life of several dozens of nuclei ranging from calcium to xenon with the shell model, and of $β β$ emitters with a wide range of proton-neutron pairing strengths in the pnQRPA, we observe good linear correlations between $2 ν β β$ - and $0 ν β β$ -decay nuclear matrix elements for both methods. We then combine the correlations with measured $2 ν β β$ -decay half-lives to predict $0 ν β β$ -decay matrix elements with theoretical uncertainties based on our systematic calculations. Our results include two-body currents and the short-range $0 ν β β$ -decay operator.
nucl-thhep-exhep-phnucl-exPRC(2023)·54 citations
02
Deep insight into charge equilibration and the effects on producing neutron-rich isotopes around N = 126 in the multinucleon transfer reactions
Zehong Liao · Long Zhu · Jun Su · Cheng Li
The dynamics of the charge equilibration (CE) and the effects on the production of the neutron-rich isotopes around $N = 126$ in multinucleon transfer reactions are still not well understood. In this Letter, we investigate the mechanism of the CE from different viewpoints by using the extended version of the dinuclear system model (DNS-sysu) and the improved quantum molecular dynamics (ImQMD) model. From the macroscopic and microscopic dynamical viewpoints, we find incomplete CE for the mass asymmetry reaction systems even in the very deep collisions, and the behavior of "inverse CE" that the tendency of the fragments is away from the $N / Z$ value of the compound system in the reaction $^{140}$ Xe + $^{198}$ Pt. Unlike the slow process presented in the ImQMD model, the behavior of fast equilibration with the characteristic time $\sim$ 0.52 zs is obtained based on the DNS-sysu model, which is consistent with the experimental data. By performing the systematic calculation, the correlation between the CE and the mass asymmetry of the reaction systems is clarified, which not only accounts for the observed intriguing phenomena of the CE but also provides essential information for producing the neutron-rich isotopes around $N = 126$ .
nucl-thPRC(2023)·20 citations
03
Second order hydrodynamics based on effective kinetic theory and electromagnetic signals from QGP
Lakshmi J. Naik🇮🇳 · V. Sreekanth🇮🇳
We study the thermal dilepton and photon production from relativistic heavy ion collisions in presence of viscosities by employing the recently developed second order dissipative hydrodynamic formulation estimated within a quasiparticle description of thermal QCD (Quantum Chromo-Dynamics) medium. The sensitivity of shear and bulk viscous pressures to the temperature dependence of relaxation time is analyzed within one dimensional boost invariant expansion of quark gluon plasma (QGP).The dissipative corrections to the phase-space distribution functions upto first order in gradients are obtained from the Chapman-Enskog like iterative solution of effective Boltzmann equation in the relaxation time approximation. Thermal dilepton and photon production rates for QGP are calculated by employing this viscous modified distribution function. Yields of these particles are quantified for the longitudinal expansion of QGP with different temperature dependent relaxation times. Our analysis employing this second order hydrodynamic model indicates that the spectra of dileptons and photons gets enhanced by both bulk and shear viscosities and is well behaved. Also, these particle yields are found to be sensitive to relaxation time. Further, we do a comparison of these particle spectra with a standard hydrodynamic formulation.
nucl-thJ.Phys.G(2023)·5 citations
04
Magnetic structure of few-nucleon systems at high momentum transfers in a $χ$ EFT approach
Alex Gnech🇺🇸 · Rocco Schiavilla🇺🇸
The five low-energy constants (LECs) in the electromagnetic current derived in chiral effective field theory ( $χ$ EFT) up to one loop are determined by a simultaneous fit to the $A$ = $2$ --3 nuclei magnetic moments and to the deuteron magnetic form factor and threshold electrodisintegration at backward angles over a wide range of momentum transfers. The resulting parametrization then yields predictions for the $^{3}$ He/ $^{3}$ H magnetic form factors in excellent accord with the experimental values for momentum transfers ranging up to $\approx 0.8$ GeV/c, beyond the expected regime of validity of the $χ$ EFT approach. The calculations are based on last-generation two-nucleon interactions including high orders in the chiral expansion and derived by Entem, Macheleidt, and Nosyk [Phys.\ Rev.\ C {\bf 96}, 024004 (2017)] and by Piarulli {\it et al.} [Phys.\ Rev.\ C {\bf 94}, 054007 (2016)], using different $χ$ EFT formulations. In the $A$ = $3$ calculations, (chiral) three-nucleon interactions are also accounted for. The model dependence resulting from these different formulations of the interactions is found to be mild for momentum transfer below $\approx 0.8$ GeV/c. An analysis of the convergence of the chiral expansion is also provided.
nucl-thPRC(2022)·18 citations
05
Energy Dependence of the Breit-Wheeler process in Heavy-Ion Collisions and its Application to Nuclear Charge Radius Measurements
Xiaofeng Wang🇨🇳 · James Daniel Brandenburg🇺🇸 · Lijuan Ruan🇺🇸 · Fenglan Shao🇨🇳 · Zhangbu Xu🇺🇸 · Chi Yang🇨🇳 · Wangmei Zha🇨🇳
The collision energy dependence of the cross section and the transverse momentum distribution of dielectrons from the Breit-Wheeler process in heavy-ion collisions are computed in the lowest-order QED and found to be sensitive to the nuclear charge distribution and the infrared-divergence of the ultra-Lorentz boosted Coulomb field. Within a given experimental kinematic acceptance, the cross section is found to increase while the pair transverse momentum ( $⟨ p_{T}^{2} ⟩$ ) decreases with increasing beam energy. We demonstrate that the transverse-momentum component of Weizsacker-Williams photons is due to the finite extent of the charge source and electric field component in the longitudinal direction. We further clarify the connection between the nuclear charge distribution and the kinematics of produced $e^{+} e^{-}$ from the Breit-Wheeler process, and propose a criterion for the validity of the Breit-Wheeler process in relativistic heavy-ion collisions. Following this approach we demonstrate that the experimental measurements of the Breit-Wheeler process in ultra-relativistic heavy-ion collisions can be used to quantitatively constrain the nuclear charge radius. The extracted parameters show sensitivity to the impact parameter dependence, and can be used to study the initial-state and final-state effects in hadronic interactions.
nucl-thhep-phnucl-exPRC(2023)·27 citations
06
Transport coefficients of second-order relativistic fluid dynamics in the relaxation-time approximation
Victor E. Ambrus · Etele Molnár · Dirk H. Rischke
We derive the transport coefficients of second-order fluid dynamics with $14$ dynamical moments using the method of moments and the Chapman-Enskog method in the relaxation-time approximation for the collision integral of the relativistic Boltzmann equation. Contrary to results previously reported in the literature, we find that the second-order transport coefficients derived using the two methods are in perfect agreement. Furthermore, we show that, unlike in the case of binary hard-sphere interactions, the diffusion-shear coupling coefficients $ℓ_{V π}$ , $λ_{V π}$ , and $τ_{V π}$ actually diverge in some approximations when the expansion order $N_{ℓ} \to \infty$ . Here we show how to circumvent such a problem in multiple ways, recovering the correct transport coefficients of second-order fluid dynamics with $14$ dynamical moments. We also validate our results for the diffusion-shear coupling by comparison to a numerical solution of the Boltzmann equation for the propagation of sound waves in an ultrarelativistic ideal gas.
nucl-thhep-phphysics.flu-dynPRD(2022)·18 citations
07
Heavy-quark potential in Gribov-Zwanziger approach around deconfinement phase transition
Wan Wu🇨🇳 · Guojun Huang🇨🇳 · Jiaxing Zhao🇨🇳 · Pengfei Zhuang🇨🇳
The interaction potential between a pair of heavy quarks is calculated with resummed perturbation method in Gribov-Zwanziger approach at finite temperature. The resummed loop correction makes the potential complex. While the real part is, as expected, screened and becomes short-ranged in hot medium, the strength of the imaginary part increases with temperature and is comparable with the real part, which is very different from the previous calculation in HTL approach. This means that, both the color screening and Landau damping play important role in the dissociation of heavy flavor hadrons in hot medium.
↳ hep-phnucl-thPRD(2023)·11 citations
08
Analysis of $Ω (2012)$ as a molecule in the chiral quark model
Xiaohuang Hu🇨🇳 · Jialun Ping🇨🇳
Inspired by the updated information on $Ω (2012)$ by the Belle Collaboration, we conduct a study of all possible $S$ -wave pentaquark systems with quark contents $sss q q ˉ, q = u, d$ in a chiral quark model with the help of Gaussian expansion method. Channel coupling is also considered. The real-scaling method (stabilization method) is employed to identify and check the bound states and the genuine resonances. In addition, the decay widths of all resonances are given. The results show that $Ω (2012)$ can be interpreted as a $Ξ^{*} K$ molecular state with quantum number of $I J^{P} = 0 (\frac{3}{2})^{-}$ . Other resonances are obtained: $Ξ^{*} K^{*}$ with $I J^{P} = 0 (\frac{1}{2})^{-}$ and $0 (\frac{3}{2})^{-}$ , $Ω π$ with $I J^{P} = 1 (\frac{3}{2})^{-}$ . These pentaquark states is expected to be further verified in future experiments.
↳ hep-phnucl-thPRD(2022)·21 citations

Affiliations

first authorsco-authorsvia INSPIRE