Nuclear Theory·nucl-th

Friday·March 8, 2024

13 papers—8 primary·5 cross-listed

01
[Submitted on 7 Mar 2024]
The stochastic relativistic advection diffusion equation from the Metropolis algorithm
Gokce Basar🇺🇸 · Jay Bhambure🇺🇸 · Rajeev Singh🇺🇸 · Derek Teaney🇺🇸
We study an approach to simulating the stochastic relativistic advection-diffusion equation based on the Metropolis algorithm. We show that the dissipative dynamics of the boosted fluctuating fluid can be simulated by making random transfers of charge between fluid cells, interspersed with ideal hydrodynamic time steps. The random charge transfers are accepted or rejected in a Metropolis step using the entropy as a statistical weight. This procedure reproduces the expected strains of dissipative relativistic hydrodynamics in a specific (and non-covariant) hydrodynamic frame known as the density frame. Numerical results, both with and without noise, are presented and compared to relativistic kinetics and analytical expectations. An all order resummation of the density frame gradient expansion reproduces the covariant dynamics in a specific model. In contrast to all other numerical approaches to relativistic dissipative fluids, the dissipative fluid formalism presented here is strictly first order in gradients and has no non-hydrodynamic modes. The physical naturalness and simplicity of the Metropolis algorithm, together with its convergence properties, make it a promising tool for simulating stochastic relativistic fluids in heavy ion collisions and for critical phenomena in the relativistic domain.
Comments:
30 pages, 6 figures. Version 2 discusses flow fields depending on space and time
Subjects:
Nuclear Theory (nucl-th); cond-mat.other (cond-mat.other); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
2403.04185 [pdf]
PRC(2024)·32 citations
02
[Submitted on 7 Mar 2024]
Analytic formula for the proton radioactivity spectroscopic factor
Dong-Meng Zhang · Lin-Jing Qi · Hai-Feng Gui · Song Luo · Biao He · Xi-Jun Wu · Xiao-Hua Li
In the present work, we systematically study the spectroscopic factor of proton radioactivity ( $S_{p}$ ) with $A > 100$ using the deformed two-potential approach (D-TPA). It is found that there is a link between the quadrupole deformation parameter of proton emitter and $S_{p}$ . Based on this result, we propose a simple analytic formula for estimating the spectroscopic factor of proton radioactivity. With the help of this formula, the calculated half-lives of proton radioactivity can reproduce the experimental data successfully within a factor of 2.77. Furthermore, we extend the D-TPA with this formula for evaluating the spectroscopic factor to predict the proton radioactivity half-lives of 12 proton radioactivity candidates whose radioactivity is energetically allowed or observed but not yet quantified in NUBASE2020. For comparison, the universal decay law for proton radioactivity (UDLP) and the new Geiger-Nuttall law (NG-N) are also used. It turns out that all of the predicted results are basically consistent with each other.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2403.04249 [pdf]
PRC(2023)·8 citations
03
[Submitted on 7 Mar 2024]
Theoretical calculations of proton emission half-lives based on a deformed Gamow-like model
Dong-Meng Zhang · Xiao-Yuan Hu · Lin-Jing Qi · Hong-Ming Liu · Ming Li · Xiao-Hua Li
In the present study, proton emission half-lives have been investigated for the deformed proton emitters with $53 \leq Z \leq 83$ in the deformed Gamow-like model, where the deformation effect has been included in the Coulomb potential. The experimental half-lives of proton emitters can be reproduced within a factor of 3.45. For comparison, other results from the universal decay law and the new Geiger-Nuttall law are presented as well. Furthermore, the relevance of the half-lives to the angular momentum $l$ for $^{117}$ La, $^{121}$ Pr, $^{135}$ Tb and $^{141}$ Ho has been analyzed, and corresponding possible values of $l$ has been put forward: $l =$ 3, 3, 4, 4.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2403.04251 [pdf]
CPC(2024)·3 citations
04
[Submitted on 7 Mar 2024]
Non-equilibrium Green's function approach to low-energy fission dynamics: fluctuations in fission reactions
K. Uzawa · K. Hagino
We present a microscopic modeling for a decay of a heavy compound nucleus, starting from a nucleonic degree of freedom. To this end, we develop an approach based on a non-equilibrium Green's function, which is combined with a configuration interaction (CI) approach based on a constrained density-functional theory (DFT). We apply this approach to a barrier-top fission of $^{236}$ U, restricting the model space to seniority zero configurations of neutrons and protons. We particularly focus on the distribution of the fission probability. We find that it approximately follows the chi-squared distribution with the number of degrees of freedom $ν$ of the order of 1, which is consistent with the experimental finding. We also show that $ν$ corresponds to the number of eigenstates of the many-body Hamiltonian whose energy is close to the excitation energy of the system and at the same time which have significant components on both sides of a fission barrier.
Comments:
12 pages, 10 figures. To appear in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Statistical Mechanics (cond-mat.stat-mech); Nuclear Experiment (nucl-ex); physics.chem-ph (physics.chem-ph)
arXiv:
2403.04255 [pdf]
PRC(2024)·4 citations
05
[Submitted on 7 Mar 2024]
Momentum correlation of light nuclei in Au + Au collisions at $s_{N N}$ = 2.0 $\sim$ 7.7 GeV
Feng-Hua Qiao🇨🇳 · Xian-Gai Deng🇨🇳 · Yu-Gang Ma🇨🇳
Within the Ultra-relativistic Quantum Molecular Dynamics model (UrQMD) coupled with nucleon coalescence model and Mini-Spanning-Tree model, the yields of light nuclei have been stimulated in Au + Au collisions over an energy range of $\sqrt{s_{NN}}=2.0\sim7.7\ \rm{GeV}$ and the momentum correlation functions of light nuclei pairs have been calculated by both the Lednický-Lyuboshitz and the Correlation After Burner methods. We compare the yields of light nuclei and their momentum correlation functions at midrapidity in this energy region with experimental data. It is found that there are differences between the results of the two models, and the coalescence method seems less valid at low collision energy. Furthermore, both the peak values of proton-proton correlation functions and the transition point of elliptic flows from out-of-plane to in-plane emission show a turning point around 3-4 GeV, which suggests that there is a relation between momentum correlation function and collective flow of particles.
Comments:
1- pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2403.04341 [pdf]
PLB(2024)·7 citations
06
[Submitted on 7 Mar 2024]
Signatures of an $α$ + core structure in $^{44}$ Ti + $^{44}$ Ti collisions at $s_{N N} = 5.02$ TeV by a multiphase transport model
Yu-Xuan Zhang🇨🇳 · Song Zhang🇨🇳 · Yu-Gang Ma🇨🇳
It is important to understand whether $α$ -clustering structures can leave traces in ultra-relativistic heavy ion collisions. Using the modified AMPT model, we simulate three $α$ + core configurations of $^{44}$ Ti in $^{44}$ Ti+ $^{44}$ Ti collisions at $s_{N N} = 5.02$ TeV as well as other systems with Woods-Saxon structures. One of these configurations has no additional constraint, but the other two have the Mott density edge $r_{Mott}$ set as either a lower or upper bound on the cluster position $r_{α}$ to check the influence of $α$ dissolution. This is the first time that the initial stage of the geometric properties in heavy-ion collisions has been configured using the traditional treatment of the nuclear structure. We compare the radial nucleon density, multiplicity distribution, transverse momentum spectra, eccentricity, triangularity, elliptic flow and triangular flow of these six systems. $α$ + core structures can alter all these observations especially in the most-central collisions, among which elliptic flow is the most hopeful as a probe of such structures.
Comments:
11 pages, 8 figures; Ero. Phys. J. A, in press (2024)
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2403.04362 [pdf]
EPJA(2024)·5 citations
07
[Submitted on 7 Mar 2024]
Medium Assisted Low Energy Nuclear Fusion
Pankaj Jain · Harishyam Kumar
We study the process of nuclear fusion at low energies in a medium using the second order time dependent perturbation theory. We consider a specific process which involves fusion of a low energy proton with a Nickel nucleus. The reaction proceeds in two steps or interactions. We refer to the amplitudes corresponding to these two interactions as the the molecular and the nuclear matrix elements. The first amplitude involves Coulomb interaction with another nucleus in the medium while the second corresponds to the nuclear fusion process. It has been shown in earlier papers that such a second order process has negligible amplitude unless it is assisted by special medium effects. In the present paper we show the presence of a special configuration of atoms which greatly enhances the process. We find that if the spacings among the atoms can be tuned, the rate can be sufficiently enhanced so that easily observable. The spacings do not require acute fine tuning, however, if they are significantly off the rate falls sharply to negligible values. This might also explain both the successes and failures experienced by many experimentalists studying this phenomenon. We study only a particular final state which involves emission of one photon. However we show that many final states are possible which need not involve photon emission.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2403.04428 [pdf]
4 citations
08
[Submitted on 7 Mar 2024]
Cluster radioactivity preformation probability of trans-lead nuclei in the scheme of NpNn
Lin-Jing Qi · Dong-Meng Zhang · Song Luo · Gui-Qing Zhang · Peng-Cheng Chu · Xi-Jun Wu · Xiao-Hua Li
In the present work, the cluster radioactivity preformation probability Pc in the scheme of NpNn for the effective number of the valence particles (holes) in trans-lead nuclei has been systematically investigated. This quantity has been explored in the simplified parametrization of NpNn as well as the multiplication NpNnI of this product with the isospin asymmetry I. The calculations for Pc are both performed in microscopic and model-dependent way. Within the microscopic approach, based on our previous work [Chin. Phys. C 47,014101 (2023)], Pc is calculated in cluster formation model (CFM) combined with the exponential relationship of Pc to the alpha decay preformation probability P alpha when the mass number of the emitted cluster Ac less than 28. While Ac greater than 28, Pc is obtained through the charge-number dependence of Pc on the decay products proposed by Ren et al. [Phys. Rev. C 70,034304 (2004)]. In the model-dependent approach, Pc is extracted through the ratios from calculated cluster radioactivity half-lives in the framework of unified fission model (UFM) proposed by Dong et al. [Eur. Phys. J. A 41,197 (2009)] to experimental ones. Both of the results show Pc in logarithmic form are linear to NpNn as well as NpNnI. For comparison, the parent-mass-number dependence analytical formula as well as the model proposed by K. Wei and H. F. Zhang [Phys. Rev. C 96,021601(R)(2017)] are also used. Furthermore, the preformation mechanic for cluster radioactivity has also been discussed.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2403.04450 [pdf]
PRC(2023)·13 citations

Affiliations

first authorsco-authorsvia INSPIRE