Nuclear Theory·nucl-th

Friday·June 21, 2024

19 papers—9 primary·10 cross-listed

01
[Submitted on 18 Jun 2024]
Parity and time-reversal violating nuclear forces with explicit $Δ$ -excitations
Lukas Gandor🇩🇪 · Hermann Krebs🇩🇪 · Evgeny Epelbaum🇩🇪
We emphasize the usefulness of treating delta resonances as explicit degrees of freedom in applications of chiral effective field theory (EFT) to parity-violating and time-reversal-violating (PVTV) nuclear interactions. Compared with the delta-less framework, the explicit inclusion of the delta isobar allows one to resum certain types of contributions to the PVTV two-pion exchange two- and three-nucleon potentials without at the same time introducing any unknown parameters up to next-to-next-to-leading order in the EFT expansion. We provide the corresponding expressions for the delta contributions in momentum and coordinate spaces and compare the convergence of the EFT expansion in both formulations.
Comments:
11 pages, 4 figures, 1 table
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2406.12980 [pdf]
EPJA(2024)·3 citations
02
[Submitted on 18 Jun 2024]
IMSRG with flowing 3 body operators, and approximations thereof
S. R. Stroberg · T. D. Morris · B. C. He
We explore the impact of retaining three-body operators within the in-medium similarity renormalization group (IMSRG), as well as various approximations schemes. After studying two toy problems, idential fermions with a contact interaction and the Lipkin-Meshkov-Glick model, we employ the valence-space formulation of the IMSRG to investigate the even- $A$ carbon isotopes with a chiral two-body potential. We find that retaining only those commutators expressions that scale as $N^{7}$ provides an excellent approximation of the full three-body treatment.
Comments:
18 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2406.13010 [pdf]
PRC(2024)·38 citations
03
[Submitted on 18 Jun 2024]
Self-consistent strong screening applied to thermonuclear reactions
Christopher Grayson🇺🇸 · Cheng Tao Yang🇺🇸 · Martin Formanek🇨🇿 · Johann Rafelski🇺🇸
Self-consistent strong plasma screening around light nuclei is implemented in the Big Bang nucleosynthesis (BBN) epoch to determine the short-range screening potential, $e ϕ (r) / T \geq 1$ , relevant for thermonuclear reactions. We numerically solve the non-linear Poisson-Boltzmann equation incorporating Fermi-Dirac statistics adopting a generalized screening mass to find the electric potential in the cosmic BBN electron-positron plasma for finite-sized $^{4}$ He nuclei as an example. Although the plasma follows Boltzmann statistics at large distances, Fermi-Dirac statistics is necessary when work performed by ions on electrons is comparable to their rest mass energy. While strong screening effects are generally minor due to the high BBN temperatures, they can enhance the fusion rates of high- $Z > 2$ elements while leaving fusion rates of lower- $Z \leq 2$ elements relatively unaffected. Our results also reveal a pronounced spatial dependence of the strong screening potential near the nuclear surface. These findings about the electron-positron plasma's role refine BBN theory predictions and offer broader applications for studying weakly coupled plasmas in diverse cosmic and laboratory settings.
Comments:
16 pages, 5 figures, typeset using LATEX default style in AASTeX631
Subjects:
Nuclear Theory (nucl-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Plasma Physics (physics.plasm-ph)
arXiv:
2406.13055 [pdf]
ApJ(2024)·5 citations
04
[Submitted on 19 Jun 2024]
The study of $0 ν β β$ decay of $^{136}$ Xe using nonclosure approach in nuclear shell model
S. Sarkar🇮🇳 · Y. Iwata🇯🇵 · K. Jha🇮🇳 · R. Chatterjee🇮🇳
In this investigation, we compute the nuclear matrix elements (NMEs) relevant to the light neutrino-exchange mechanism governing neutrinoless double beta ( $0 ν β β$ ) decay in $^{136}$ Xe. Our method is based on the nonclosure approach within the interacting nuclear shell model framework. This approach considers the genuine effects arising from the excitation energies of two hundred states for each spin-parity of the intermediary nucleus $^{136}$ Cs. All computations are performed using the effective shell model Hamiltonian GCN5082. To understand the impact of nuclear structure on $0 ν β β$ decay, we explore the dependence of the NME on various factors, including the number of intermediate states and their spin-parity characteristics. We identify an optimal closure energy of approximately 3.7 MeV for the $0 ν β β$ decay of $^{136}$ Xe that reproduces the nonclosure NME using the closure approach. The calculated total NME for the light neutrino-exchange $0 ν β β$ decay of $^{136}$ Xe is 2.06 with the CD-Bonn short-range correlation (SRC). These results can be valuable for future experimental investigations into the $0 ν β β$ decay of $^{136}$ Xe.
Comments:
10 pages, and 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2406.13417 [pdf]
PRC(2025)·1 citation
05
[Submitted on 19 Jun 2024]
Energy dependence of particle production in Au+Au collisions at $s_{NN}$ = 7.7-200 GeV using a multiphase transport model
Krishan Gopal · Chitrasen Jena · Kishora Nayak
In this study, we employ a multi-phase transport (AMPT) model to understand the production of $π^{\pm}$ , $K^{\pm}$ , $p$ , $p$ , $K_{s}^{0}$ , $Λ$ , $Λ ˉ$ , and $ϕ$ in Au + Au collisions at $s_{N N} = 7.7$ , $27$ , $39$ , $62.4$ , and $200$ GeV. We have studied the energy dependence of various bulk properties of the system such as transverse momentum ( $p_{T}$ ) spectra, particle yields ( $d N / d y$ ), mean transverse mass ( $⟨ m_{T} ⟩$ ), and anti-particle to particle ratios. Model calculations using both default and string melting versions of the AMPT with three distinct sets of initial conditions are compared to the data from the STAR experiment. In the case of $π^{\pm}$ , $K^{\pm}$ , $p$ , and $p$ , we observe that the string melting version shows better agreement with data at higher energies, while the default version performs better at lower collision energies. However, for $K_{s}^{0}$ , $Λ$ , and $ϕ$ , it is observed that the default version is able to describe the data better at all energies. In addition, we have used the blast-wave model to extract the kinetic freeze-out properties, like the kinetic freeze-out temperature and the radial flow velocity. We observe that these parameters are comparable with the data.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2406.13520 [pdf]
1 citation
06
[Submitted on 19 Jun 2024]
Beyond modified Urca: the nucleon width approximation for flavor-changing processes in dense matter
Mark G. Alford🇺🇸 · Alexander Haber🇺🇸 · Ziyuan Zhang🇺🇸
Flavor-changing charged current ("Urca") processes are of central importance in the astrophysics of neutron stars. Standard calculations approximate the Urca rate as the sum of two contributions, direct Urca and modified Urca. Attempts to make modified Urca calculations more accurate have been impeded by an unphysical divergence at the direct Urca threshold density. In this paper we describe a systematically improvable approach where, in the simplest approximation, instead of modified Urca we include an imaginary part of the nucleon mass (nucleon width). The total Urca rate is then obtained via a straightforward generalization of the direct Urca calculation, yielding results that agree with both direct and modified Urca at the densities where those approximations are valid. At low densities, we observe an enhancement of the rate by more than an order of magnitude, with important ramifications for neutron star cooling and other transport properties.
Comments:
6 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2406.13717 [pdf]
PRC(2024)·26 citations
07
[Submitted on 19 Jun 2024]
Revealing initial state properties through ultra-central symmetric heavy-ion collisions
S. M. A. Tabatabaee🇮🇷 · S. F. Taghavi🇩🇪
Heavy-ion experiments provide a new opportunity to gain a deeper understanding of the structure of nuclei. To achieve this, it is crucial to identify observables under circumstances that are minimally affected by the process that leads to the initial state of heavy-ion collisions from nuclear wavefunction. In this study, we demonstrate that when assuming scale-invariance, the effect of this stage on the initial energy or entropy density moments in ultra-central symmetric collisions is negligible for nucleon sizes of approximately 0.7 fm or larger for large nuclei. By borrowing cluster expansion method from statistical physics and using scale-invariance assumption, we calculate the average ellipticity of initial density at the presence of short-range correlation. We compare our calculations to Monte Carlo studies and assess the accuracy of various methods of short-range correlation sampling. Additionally, we find that the isobar ratio can constrain the initial state parameters, in addition to deformation. Our study indicates that the isobar ratios in ultra-central collisions are especially sensitive to the fluctuation in the weight of the nuclei constituents and the two-body correlation among nucleons. This insight is crucial for drawing conclusions about nuclear deformations based on isobar ratios.
Comments:
32 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2406.13863 [pdf]
PRC(2024)·4 citations
08
[Submitted on 20 Jun 2024]
Faddeev calculations of low-energy $Λ$ -deuteron scattering and momentum correlation function
M. Kohno🇯🇵 · H. Kamada🇯🇵
Faddeev calculations of low-energy $Λ$ -deuteron elastic scattering are performed up to $E_{c m} = 20$ MeV across the deuteron threshold. Phase shifts of the $s$ -wave with $J = 1/2$ and $J = 3/2$ are calculated using strangeness $S = - 1$ hyperon-nucleon interactions in chiral effective field theory NLO13 and NLO19 parametrized by the Jülich-Bonn group. Effective range parameters, such as a scattering length and an effective range, are determined through the calculated phase shifts. $Λ$ -deuteron momentum correlation functions are evaluated using the $Λ$ -deuteron relative wave function constructed from half-off-shell $t$ -matrices. They are compared with those evaluated using an approximate formula.
Comments:
10 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2406.13899 [pdf]
PRC(2024)·7 citations
09
[Submitted on 20 Jun 2024]
Hydrodynamic-like behaviour of glasma
Margaret E. Carrington🇨🇦 · Stanislaw Mrowczynski🇵🇱 · Jean-Yves Ollitrault🇫🇷
At the earliest stage of ultrarelativistic heavy-ion collisions the produced matter is a highly populated system of gluons called glasma which can be approximately described in terms of classical chromodynamic fields. Although the system's dynamics is governed by Yang-Mills equations, glasma evolution is shown to strongly resemble hydrodynamic behaviour.
Comments:
20 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2406.14463 [pdf]
PRC(2024)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE