Nuclear Theory·nucl-th

Tuesday·December 24, 2024

16 papers—7 primary·9 cross-listed

01
[Submitted on 20 Dec 2024]
B(E2) strength in $^{36, 38}$ Ca and in mirror nuclei 36S, 38Ar
Jacek Okolowicz🇵🇱 · Marek Ploszajczak🇫🇷
Recently, $B (E 2, 0_{1}^{+} \to 2_{1}^{+})$ transition strength have been measured in $^{36}$ Ca and $^{38}$ Ca. Surprisingly, the measured value in $^{36}$ Ca: $B (E 2 ↑) = 131 (20)$ e $^{2}$ fm $^{4}$ , is significantly larger than in $^{38}$ Ca, where $B (E 2 ↑) = 101 (11)$ e $^{2}$ fm $^{4}$ , whereas an opposite tendency of $B (E 2)$ values is seen in the mirror nuclei $^{36}$ S and $^{38}$ Ar. The resonance $2_{1}^{+}$ in $^{36}$ Ca lies 465 keV above the proton emission threshold and its description requires inclusion of the coupling to the continuum. In this work, we are analyzing $B (E 2 ↑)$ values in $^{36}$ Ca, $^{36}$ S, $^{38}$ Ca, and $^{38}$ Ar using the real-energy continuum shell model, the so-called shell model embedded in the continuum, in the $(1 s_{1/2} 0 d_{3/2} 0 f_{7/2} 1 p_{3/2})$ model space with the monopole adjusted effective interaction ZBM-IO.
Comments:
12 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2412.16362 [pdf]
Acta Phys.Polon.Supp.(2025)·1 citation
02
[Submitted on 21 Dec 2024]
Nuclear structure properties of $^{193 - 200}$ Hg isotopes within large-scale shell model calculations
Subhrajit Sahoo · Praveen C. Srivastava · Noritaka Shimizu · Yutaka Utsuno
Large-scale shell-model calculations have been performed to study the nuclear structure properties of Hg isotopes with mass varying from $A = 193$ to $A = 200$ . The shell-model calculations are carried out in the 50 $\leq Z \leq$ 82 and 82 $\leq N \leq$ 126 model space using monopole-based truncation. We present detailed studies on low-energy excitation spectra, energy systematics, and collective properties of Hg isotopes, such as reduced transition probabilities, quadrupole, and magnetic moments along the isotopic chain. The evolution of wave function configurations with spin is analyzed in the case of even- $A$ Hg isotopes. The shell-model results are in reasonable agreement with the experimental data and predictions are made where experimental data are unavailable. The shapes of Hg isotopes are also investigated through the energy-surface plots.
Comments:
18 pages, 18 figures and 4 tables
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2412.16518 [pdf]
PRC(2024)·6 citations
03
[Submitted on 21 Dec 2024]
Reaction mechanism of quasi-free knockout processes in exotic RI beam era
Kazuki Yoshida · Junki Tanaka
The quasi-free nucleon knockout reaction has been revealed the single-particle nature of nuclei. Thanks to the advances in experimental techniques and reaction theory, various new aspects of nuclei are being revealed by knockout reactions. In this article, we review the basic concept of the quasi-free knockout reaction, and recent achievements in the SEASTAR project using the MINOS system. We also present our new findings on the low-energy nucleon knockout reaction and the $α$ knockout reaction. The combination of the (microscopic) structure theory, reaction theory and experiments will be the key to a complete understanding of the $α$ formation and its universality in the coming decades. Noble clusters, e.g., $d$ , $t$ , $^{3}$ He, etc. are in the scope of the ONOKORO project. The implementation of the two (and more) nucleon correlation in the reaction theory is essential to connect the properties of such clusters and the reaction observables. A new framework, CDCCIA, is introduced for this purpose, which will also be applicable to the two-nucleon knockout reactions, e.g., $(p, 3 p)$ , $(p, 2 p n)$ , and $(p, p 2 n)$ .
Comments:
Contribution to review article for the symposium "Direct reactions and spectroscopy with hydrogen targets: past 10 years at the RIBF and future prospects", 33 pages, 13 figures, to be submitted to PTEP
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2412.16649 [pdf]
PTEP(2026)·2 citations
04
[Submitted on 22 Dec 2024]
Radiative Energy Loss in a Temperature-Evolving QGP with Dynamical Constituents
Bithika Karmakar🇨🇿 · Magdalena Djordjevic🇷🇸
We present a theoretical formalism for calculating first-order-in-opacity radiative energy loss that incorporates the spatial and temporal temperature evolution of the quark-gluon plasma (QGP) in a finite-size QCD medium with dynamical (i.e., moving) constituents. The derived expressions allow for arbitrary temperature profiles, enabling detailed evaluations of radiative energy loss across different medium-evolution scenarios. Importantly, the resulting kernel applies to both single partons (R = 0) and jets (R > 0) via an out-of-cone selection, providing a unified starting point for precision QGP tomography.
Comments:
41 pages, 12 figures: A section and a figure have been added
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2412.17106 [pdf]
PRC(2026)·2 citations
05
[Submitted on 23 Dec 2024]
Effects of a first-order QCD phase transition on light nucleus production
He Liu🇨🇳 · Kai-Jia Sun🇨🇳 · Peng-Cheng Chu🇨🇳
Using an extended Polyakov-looped Nambu--Jona-Lasinio (PNJL) model to describe the baryon density fluctuations of quark matter along the isentropic trajectories corresponding to different $s / ρ_{B}$ values extracted from Au+Au collisions at energies $s_{N N} = 7.7 - 200$ GeV, we investigate the effects of the first-order phase transition on the light nucleus yield ratio $N_{t} \times N_{p} / N_{d}^{2}$ . The results indicate that the second-order scaled density moment $y_{2}$ , used to quantify density fluctuations, rapidly increases to form a peak when the isentropic trajectories pass through the phase coexistence region. We extract the yield ratios $N_{t} \times N_{p} / N_{d}^{2}$ at chemical freeze-out from the isentropic trajectories at different collision energies and found significant enhancements at 19.6 GeV and 27 GeV. This is similar to the trends observed by the STAR experiment, suggesting that the enhancements in the yield ratios $N_{t} \times N_{p} / N_{d}^{2}$ observed in the STAR experiment could be explained by the density fluctuations generated in the first-order phase transition region.
Comments:
8 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2412.17621 [pdf]
1 citation
06
[Submitted on 23 Dec 2024]
Axion effects on quark matter and quark-matter cores in massive hybrid stars
He Liu🇨🇳 · Yu-Heng Liu🇨🇳 · Yong-Hang Yang🇨🇳 · Min Ju🇨🇳 · Xu-Hao Wu🇨🇳 · Hong-Ming Liu🇨🇳 · Peng-Cheng Chu🇨🇳
Using a three-flavor Nambu--Jona-Lasinio model to describe the charge-parity violating effects through axion field, we investigate the axion effects on quark matter and quark-matter cores in massive hybrid stars. The properties of quark matter vary with the scaled axion field $a / f_{a}$ in a periodic manner, with a period of $2 π$ . Within the range from 0 to $π$ , axion field decrease the baryon chemical potential of the first-order phase transition, leading to an increase in normalized pressure and stiffening of the quark matter equation of state. The effect of axions on hybrid star matter that includes the hadron-quark phase transition is contrary to expectations. The axion field shifts the onset of the hadron-quark mixed phase to lower densities but slightly softens the equation of state of the mixed phase matter, which also results in a slight decrease in the maximum mass and corresponding radius of the hybrid stars. However, we also find that the lowering of the onset of the mixed phase significantly increases the radius and mass of the quark-matter core in the hybrid star. Therefore, our results indicate with axion effects, a sizable quark-matter core can appear in $2 M_{⊙}$ massive neutron stars.
Comments:
6 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2412.17624 [pdf]
PRD(2025)·6 citations
07
[Submitted on 23 Dec 2024]
Electromagnetic Selection Rules for $^{24} Mg$ in a $6 α$ Cluster Model with $D_{4 h}$ Symmetry
Gianluca Stellin🇫🇷 · Karl-Heinz Speidel🇩🇪
In the framework of a macroscopic $α$ -cluster model, the structural properties and the spectroscopy of the $^{24} Mg$ nucleus are investigated. Special attention is devoted to the electromagnetic selection rules imposed by the point-symmetry group $D_{4 h}$ that leaves invariant the adopted $6 α$ equilibrium configuration, a square bipyramid. The analysis entails the application of group-theoretical identities and character tables, in a way familiar to quantum chemists. The results show that the occurrence of interband E0, E2, and M1, M2, M3 transitions is strictly regulated by the transformation properties of the excited vibrational modes to which the states in the process belong. Unlike the $^{12} C$ nucleus in the $D_{3 h}$ -symmetric $3 α$ arrangement, M1 transition channels are active between states corresponding to a single quantum of vibrational excitation. Conversely, the measured E1 strengths in the $^{24} Mg$ spectrum are attributable to the excitation of single-nucleon degrees of freedom, as E1 transitions are forbidden by the model. The present investigation is a only part of a wider work, encompassing the spectrum and the whole electromagnetic properties of this nucleus in the considered $D_{4 h}$ -symmetric configuration, in preparation.
Comments:
21 pages, 10 tables, 2 figures. Submitted to the Journal of Physics G
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2412.17782 [pdf]
J.Phys.G(2026)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE

B(E2) strength in 36,38Ca and in mirror nuclei 36S, 38Ar

Nuclear structure properties of 193−200Hg isotopes within large-scale shell model calculations

Reaction mechanism of quasi-free knockout processes in exotic RI beam era

Radiative Energy Loss in a Temperature-Evolving QGP with Dynamical Constituents

Effects of a first-order QCD phase transition on light nucleus production

Axion effects on quark matter and quark-matter cores in massive hybrid stars

Electromagnetic Selection Rules for 24Mg in a 6α Cluster Model with D4h​ Symmetry

Affiliations

B(E2) strength in $^{36, 38}$ Ca and in mirror nuclei 36S, 38Ar

Nuclear structure properties of $^{193 - 200}$ Hg isotopes within large-scale shell model calculations

Electromagnetic Selection Rules for $^{24} Mg$ in a $6 α$ Cluster Model with $D_{4 h}$ Symmetry