Nuclear Theory·nucl-th

Friday·February 21, 2025

8 papers—4 primary·4 cross-listed

01
[Submitted on 19 Feb 2025]
Puzzling $B (E 2; 0^{+} \to 2^{+})$ strength in the proton dripline nucleus $^{36}$ Ca
Z. C. Xu · S. M. Wang · T. Beck · A. Gade · W. Nazarewicz
Recent measurements of the $E 2$ transition rate from the ground state to the first 2 $^{+}$ excited state of the proton dripline nucleus $^{36}$ Ca show an unusual pattern when compared to its isotopic neighbor $^{38}$ Ca: despite having a higher $E_{x} (2_{1}^{+})$ excitation energy, the $B (E 2; 0_{1}^{+} \to 2_{1}^{+})$ rate in $^{36}$ Ca is larger. The question that naturally arises is to what extent this observation can be attributed to the unbound character of the $2_{1}^{+}$ state. To understand the influence of the continuum space on the low-energy properties of $^{36}$ Ca, we carried out Gamow shell model calculations that can account for the continuum coupling effects associated with the occupation of unbound $f p$ shells. We found that in the threshold $2^{+}$ state, $^{36}$ Ca is spatially diffused, which impacts the observed $B (E 2)$ trend.
Comments:
6 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2502.14106 [pdf]
PRC(2025)·3 citations
02
[Submitted on 20 Feb 2025]
Thermal and baryon density modifications to the $σ$ -boson propagator: A road to describe the transfer of vorticity to spin in a nuclear environment in relativistic heavy-ion collisions
Alejandro Ayala🇲🇽 · José Jorge Medina-Serna🇲🇽 · Isabel Domínguez🇲🇽 · Ivonne Maldonado🇷🇺 · María Elena Tejeda-Yeomans🇲🇽
In the context of the description of how the vortical motion, produced in peripheral heavy-ion collisions, is transferred to the spin of hadrons, we compute the $σ$ -meson propagator at finite temperature and baryon density. This propagator encodes the properties of a medium consisting mainly of nucleons{, and can be used to model the main interactions between hadrons} in the corona region of the reaction. We compute the one-loop $σ$ self-energy in an approximation that accounts for the large nucleon mass. From the real part of the self-energy, we find the dispersion relation and show that the $σ$ -mass receives a non-negligible thermal and baryon chemical dependent {contribution}. From the imaginary part, we also compute the spectral density, which we show to contain a piece coming from the branch cut associated with Landau damping. We also present approximations for the dispersion relation and the residue at the pole in the small- and large-momentum regimes and complement the calculation, providing the sum rules satisfied by the propagator. This study aims to determine one of the elements needed to compute how the vortical motion in the corona region of the reaction is transferred to the spin of $Λ$ hyperons that can interact with nucleons by $σ$ -meson exchange.
Comments:
9 pages, 5 figues
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2502.14248 [pdf]
0 citations
03
[Submitted on 20 Feb 2025]
Hyper-neutron stars from an ab initio calculation
Hui Tong🇩🇪 · Serdar Elhatisari🇩🇪 · Ulf-G. Meißner🇩🇪
The equation of state (EoS) of neutron matter plays a decisive role to understand the neutron star properties and the gravitational waves from neutron star mergers. At sufficient densities, the appearance of hyperons generally softens the EoS, leading to a reduction in the maximum mass of neutron stars well below the observed values of about 2 solar masses. Even though repulsive three-body forces are known to solve this so-called ``hyperon puzzle'', so far performing \textit{ab initio} calculations with a substantial number of hyperons for neutron star properties has remained elusive. Starting from the newly developed auxiliary field quantum Monte Carlo algorithm to simulate hyper-neutron matter (HNM) without any sign oscillations, we derive three distinct EoSs by employing the state-of-the-art Nuclear Lattice Effective Field Theory. We include $N Λ$ , $ΛΛ$ two-body forces, $N N Λ$ , and $N ΛΛ$ three-body forces. Consequently, we determine essential astrophysical quantities such as the neutron star mass, radius, tidal deformability, and the universal $I$ -Love- $Q$ relation. The maximum mass, radius and tidal deformability of a $1.4 M_{⊙}$ neutron star are predicted to be $2.17 (1) (1) M_{⊙}$ , $R_{1.4 M ⊙} = 13.10 (1) (7)$ km, and $Λ_{1.4 M_{⊙}} = 597 (5) (18)$ , respectively, based on our most realistic EoS. These predictions are in good agreement with the latest astrophysical constraints derived from observations of massive neutron stars, gravitational waves, and joint mass-radius measurements. Also, for the first time in \textit{ab initio} calculations, we investigate both non-rotating and rotating neutron star configurations. The results indicate that the impact of rotational dynamics on the maximum mass is small, regardless of whether hyperons are present in the EoS or not.
Comments:
16 pages, 9 figures. arXiv admin note: substantial text overlap with arXiv:2405.01887
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2502.14435 [pdf]
ApJ(2025)·19 citations
04
[Submitted on 20 Feb 2025]
Neutron versus proton scattering on exotic nuclei: the $^{9}$ He example
M. S. Khirk (1) · L. V. Grigorenko (1, 2, 3) · D. E. Lanskoy (4) · P. G. Sharov (5) ((1) Flerov Laboratory of Nuclear Reactions, JINR, Dubna, Russia, (2) National Research Nuclear University "MEPhI'', Moscow, Russia, (3) National Research Centre "Kurchatov Institute'', Moscow, Russia, (4) Faculty of Physics, Lomonosov Moscow State University, Moscow, Russia, (5) Institute of Physics in Opava, Silesian University in Opava, Opava, Czech Republic)
Neutron scattering on exotic nuclides is a class of processes which can not be studied directly now and in any observable future. Resonance proton scattering of exotic nuclide on a thick target in inverse kinematics can be used to infer the properties of the low-energy neutron scattering of this nuclide assuming the isobaric symmetry. However, the results of such resonance proton scattering reactions are so far analyzed in theoretical approaches (optical, R-matrix models), which are missing important aspects of isospin dynamics, isospin violation in continuum and threshold dynamics. The isospin conserving coupled-channel model (ICM) is proposed, which provides a more reliable basis for understanding of such experimental studies. Qualitatively different phase shifts for the $^{8}$ He+ $p$ $T = 5/2$ and $T = 3/2$ resonances are predicted by ICM with quite unusual profile for the $T = 5/2$ states. Alternative interpretation of the existing $^{8}$ He+ $p$ data is proposed. The observable properties of the $T = 5/2$ resonances may be strongly affected by the isobaric-partner $T = 3/2$ states. Crucial importance of studies of the neutron-emission channel for disentangling this possible influence is demonstrated.
Comments:
7 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2502.14595 [pdf]
PRC(2025)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Puzzling B(E2;0+→2+) strength in the proton dripline nucleus 36Ca

Thermal and baryon density modifications to the σ-boson propagator: A road to describe the transfer of vorticity to spin in a nuclear environment in relativistic heavy-ion collisions

Hyper-neutron stars from an ab initio calculation

Neutron versus proton scattering on exotic nuclei: the 9He example

Affiliations

Puzzling $B (E 2; 0^{+} \to 2^{+})$ strength in the proton dripline nucleus $^{36}$ Ca

Thermal and baryon density modifications to the $σ$ -boson propagator: A road to describe the transfer of vorticity to spin in a nuclear environment in relativistic heavy-ion collisions

Neutron versus proton scattering on exotic nuclei: the $^{9}$ He example