Nuclear Theory·nucl-th

Tuesday·July 9, 2024

15 papers—7 primary·8 cross-listed

01
[Submitted on 3 Jul 2024]
Magnetic structure of $A \leq 10$ nuclei using the Norfolk nuclear models with quantum Monte Carlo methods
G. Chambers-Wall🇺🇸 · A. Gnech🇺🇸 · G. B. King🇺🇸 · S. Pastore🇺🇸 · M. Piarulli🇺🇸 · R. Schiavilla🇺🇸 · R. B. Wiringa🇺🇸
We present Quantum Monte Carlo calculations of magnetic moments, form factors, and densities of $A \leq 10$ nuclei within a chiral effective field theory approach. We use the Norfolk two- and three-body chiral potentials and their consistent electromagnetic one- and two-nucleon current operators. We find that two-body contributions to the magnetic moment can be large (up to $\sim 33%$ in $A = 9$ systems). We study the model dependence of these observables and place particular emphasis on investigating their sensitivity to using different cutoffs to regulate the many-nucleon operators. Calculations of elastic magnetic form factors for $A \leq 10$ nuclei show excellent agreement with the data out to momentum transfers $q \approx 3$ fm $^{- 1}$ .
Comments:
25 pages, 14 figures, 6 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2407.04744 [pdf]
PRC(2024)·15 citations
02
[Submitted on 7 Jul 2024]
Statistical Production of $B_{c}$ Mesons in Heavy-Ion Collisions at the LHC Energy
Shouxing Zhao🇨🇳 · Min He🇨🇳
The recombination production of $B_{c}$ mesons in heavy-ion collisions at the LHC energy is facilitated by the abundant and highly thermalized charm ( $c$ ) quarks transported in the deconfined medium created. We study the production of $B_{c}$ mesons via $c$ and bottom ( $b$ ) quark recombination in a statistical fashion by placing $B_{c}$ in the position of a member of the family of open $b$ hadrons, which allows us to make quantitative predictions for the modifications of the production fraction ( $f_{c}$ ) of $B_{c}$ mesons and its relative production to $B$ mesons in $s_{NN} = 5.02$ TeV Pb-Pb collisions with respect to proton-proton ( $pp$ ) collisions at the same energy. The statistical production yield of $B_{c}$ mesons is converted into the transverse momentum ( $p_{T}$ ) distribution with the shape computed from resonance recombination using the $c$ - and $b$ -quark phase space distributions that have been simulated via Langevin diffusion and constrained by open $c$ - and $b$ -hadron observables. Supplemented with the component fragmented from $b$ -quark spectrum that dominates at high $p_{T}$ , the total $p_{T}$ spectrum of $B_{c}$ mesons is obtained and converted into the $p_{T}$ dependent nuclear modification factor ( $R_{AA}$ ). Both $f_{c}$ and the integrated $R_{AA}$ exhibit a $\sim 5$ -fold enhancement in central Pb-Pb collisions relative to the $pp$ reference. Comparison with data measured by the CMS experiment shows decent agreement within theoretical and experimental uncertainties.
Comments:
10 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2407.05234 [pdf]
PLB(2025)·6 citations
03
[Submitted on 7 Jul 2024]
Quantifying angular distributions in multinucleon transfer reactions with a semi-classical method
Zehong Liao · Zepeng Gao · Yu Yang · Yueping Fang · Jun Su · Long Zhu
The multinucleon transfer (MNT) process in low-energy heavy ion collisions can be utilized to produce unknown nuclei far beyond the stability line. However, the reaction products exhibit broad angular and energy distributions, which could lower the experimental detection efficiency. We present a classical approach that employs a parameterized angular distribution to describe the complex issue. By analyzing limited experimental data on angular distribution, we proposed a three-parameter formula to calculate the angular distribution and identified the dependencies of the parameters. We also discuss the sensitivity of these parameters within this method. A comprehensive comparison with microscopic models and experimental data across a wide range of conditions is conducted. The proposed formula offers an efficient and straightforward way to determine the angular distribution of MNT products.
Comments:
6 pages, 6 figure
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2407.05395 [pdf]
PRC(2025)·3 citations
04
[Submitted on 8 Jul 2024]
Significance of tensor force in pseudo-spin symmetry
H. Nakada · T. Inakura
We point out that the pseudo-spin symmetry (PSS) of nuclei significantly depends on the proton ( $Z$ ) and neutron numbers ( $N$ ), sometimes giving rise to the characteristic structures. By using the non-relativistic spherical Hartree-Fock calculation with a realistic tensor force, we show that the tensor force may be deeply relevant to the $Z$ - and $N$ -dependence of the PSS. While the PSS has often been discussed in the context of the relativistic symmetry, the tensor-force effects on the PSS sometimes look analogous to the $Z$ -and $N$ -dependence of the PSS in the relativistic mean-field (RMF) calculations without explicit tensor force. The observed variation of the $p 0 d_{3/2}$ - $p 1 s_{1/2}$ levels from $^{40}$ Ca to $^{34}$ Si is consistent with the tensor-force-driven $Z$ -dependence of the PSS, but not necessarily with the RMF result. Even though it is too early to be conclusive, this result elucidates the significance of the tensor force when discussing the PSS.
Comments:
to appear in PRC
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2407.05524 [pdf]
PRC(2024)·5 citations
05
[Submitted on 8 Jul 2024]
Volume effect on the extraction of sound velocity in high-energy nucleus-nucleus collisions
Jing-An Sun🇨🇳 · Li Yan🇨🇳
The determination of the speed of sound in quark-gluon plasma is a crucial aspect of understanding the properties of strongly interacting matter created in relativistic heavy-ion collisions. In this study, we investigate the impact of initial-state fluctuations on the extraction of the speed of sound in a quark-gluon plasma in the ultra-central collisions. By employing the TRENTo model for simulating initial conditions, we demonstrate that these fluctuations lead to sizable volume effect, which in turn corrects the measured values of the sound velocity. With respect to realistic conditions of high-energy heavy-ion experiments, we provide quantitative estimate of these corrections.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2407.05570 [pdf]
PLB(2025)·9 citations
06
[Submitted on 8 Jul 2024]
Surface and curvature tensions of cold dense quark matter: a term-by-term analysis within the Nambu-Jona-Lasinio model
A. G. Grunfeld🇦🇷 · M. F. Izzo Villafañe🇦🇷 · G. Lugones🇧🇷
In this paper, we conduct a thorough investigation of the surface and curvature tensions, $σ$ and $γ$ , of three-flavor cold quark matter using the Nambu-Jona-Lasinio (NJL) model with vector interactions. Our approach ensures both local and global electric charge neutrality, as well as chemical equilibrium under weak interactions. By employing the multiple reflection expansion formalism to account for finite size effects, we explore the impact of specific input parameters, particularly the vector coupling constant ratio $η_{V}$ , the radius $R$ of quark matter droplets, as well as charge-per-baryon ratio $ξ$ of the finite size configurations. We focus on the role of the contributions of each term of the NJL Lagrangian to the surface and curvature tensions in the mean field approximation. We find that the total surface tension exhibits two different density regimes: it remains roughly constant at around $100 MeV f m^{- 2}$ up to approximately $2 - 4$ times the nuclear saturation density, and beyond this point, it becomes a steeply increasing function of $n_{B}$ . The total surface and curvature tensions are relatively insensitive to variations in $R$ but are affected by changes in $ξ$ and $η_{V}$ . We observe that the largest contribution to $σ$ and $γ$ comes from the regularized divergent term, making these quantities significantly higher than those obtained within the MIT bag model.
Comments:
12 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2407.05606 [pdf]
Universe(2025)·3 citations
07
[Submitted on 8 Jul 2024]
Magnetic dipole $γ$ -ray strength functions in the crossover from spherical to deformed neodymium isotopes
A. Mercenne · P. Fanto · W. Ryssens · Y. Alhassid
We calculate the magnetic dipole $γ$ -ray strength functions in a chain of even-mass neodymium isotopes $^{144 - 152}$ Nd in the framework of the configuration-interaction (CI) shell model. We infer the strength function by applying the maximum entropy method (MEM) to the exact imaginary-time response function calculated with the shell-model Monte Carlo (SMMC) method. The success of the MEM depends on the choice of a good strength function as a prior distribution. We investigate two choices for the prior strength function: the static path approximation (SPA) and the quasiparticle random-phase approximation (QRPA). We find that the QRPA is a better approximation at low temperatures (i.e., near the ground state), while the SPA is a better choice at finite temperatures. We identify a low-energy enhancement (LEE) in the MEM deexcitation $M 1$ strength functions of the even-mass neodymium isotopes and compare with recent experimental results for the total deexcitation $γ$ -ray strength functions. The LEE is already seen in the SPA strength function but not in the QRPA strength function, indicating the importance of large-amplitude static fluctuations around the mean field in reproducing the LEE. Our method is currently the only one which can reproduce LEE in heavy open-shell nuclei where conventional CI shell model calculations are prohibited. With the onset of deformation as number of neutrons increases along the chain of neodymium isotopes, we observe that some of the LEE strength transfers to a low-energy excitation, which we interpret as a finite-temperature "scissors" mode. We also observe a finite-temperature spin-flip mode.
Comments:
11 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2407.06161 [pdf]
PRC(2024)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE

Magnetic structure of A≤10 nuclei using the Norfolk nuclear models with quantum Monte Carlo methods

Statistical Production of Bc​ Mesons in Heavy-Ion Collisions at the LHC Energy

Quantifying angular distributions in multinucleon transfer reactions with a semi-classical method

Significance of tensor force in pseudo-spin symmetry

Volume effect on the extraction of sound velocity in high-energy nucleus-nucleus collisions

Surface and curvature tensions of cold dense quark matter: a term-by-term analysis within the Nambu-Jona-Lasinio model

Magnetic dipole γ-ray strength functions in the crossover from spherical to deformed neodymium isotopes

Affiliations

Magnetic structure of $A \leq 10$ nuclei using the Norfolk nuclear models with quantum Monte Carlo methods

Statistical Production of $B_{c}$ Mesons in Heavy-Ion Collisions at the LHC Energy

Magnetic dipole $γ$ -ray strength functions in the crossover from spherical to deformed neodymium isotopes