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
05
[Submitted on 19 Feb 2025] (cross-list from physics.plasm-ph)
Temperature Dependence of Beam on Plasma Stopping Power in the Resonance Regions of Fusion Reactions
Keh-Fei Liu🇺🇸
A recent proposal of accelerator based fusion reactor considers a scheme where an ion beam from the accelerator hits the target plasma on the resonance of the fusion reaction so that the reactivity ( $σ v$ ) can be an order of magnitude larger than that of a thermonuclear reactor. One of the important inputs is the stopping power which is needed to assess the energy loss of the beam in the plasma. In this work, we shall use the analytic formulation of Brown, Preston and Singleton~\cite{Brown:2005ji} to calculate the temperature dependence of the stopping power due to the target $t,^{3} H_{e}$ , and $^{11} B$ plasmas in the resonance regions of their respective fusion reactions, i.e., $d + t \to n + α, d +^{3} H_{e} \to p + α$ , and $p +^{11} B \to 3 α$ . It is found that the calculated stopping power, especially when the quantum corrections are included, does not go down with temperature as fast at $T^{- 3/2}$ . Instead it decreases slower, more like $T^{- x}$ with $x \leq 1$ in the range of T from $\sim$ 5 to 50 keV for $d$ on $t$ and $^{3} H_{e}$ plasmas around their resonance energies.
Comments:
9 pages, 6 figures
Subjects:
Plasma Physics (physics.plasm-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Accelerator Physics (physics.acc-ph)
arXiv:
2502.14098 [pdf]
Plasma Phys.(2024)·0 citations
06
[Submitted on 20 Feb 2025] (cross-list from hep-lat)
QCD predictions for physical multimeson scattering amplitudes
Sebastian M. Dawid🇺🇸 · Zachary T. Draper🇺🇸 · Andrew D. Hanlon🇺🇸 · Ben Hörz🇩🇪 · Colin Morningstar🇺🇸 · Fernando Romero-López🇨🇭 · Stephen R. Sharpe🇺🇸 · Sarah Skinner🇺🇸
We use lattice QCD calculations of the finite-volume spectra of systems of two and three mesons to determine, for the first time, three-particle scattering amplitudes with physical quark masses. Our results are for combinations of $π^{+}$ and $K^{+}$ , at a lattice spacing $a = 0.063$ fm, and in the isospin-symmetric limit. We also obtain accurate results for maximal-isospin two-meson amplitudes, with those for $π^{+} K^{+}$ and $2 K^{+}$ being the first determinations at the physical point. Dense lattice spectra are obtained using the stochastic Laplacian-Heaviside method, and the analysis leading to scattering amplitudes is done using the relativistic finite-volume formalism. Results are compared to chiral perturbation theory and to phenomenological fits to experimental data, finding good agreement.
Comments:
7 pages, 4 figures, 2 tables. v3: minor updates in figs 3,4. Matches published version
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2502.14348 [pdf]
PRL(2025)·22 citations
07
[Submitted on 20 Feb 2025] (cross-list from hep-ex)
Efficient Monte Carlo Event Generation for Neutrino-Nucleus Exclusive Cross Sections
Mathias El Baz🇨🇭 · Federico Sánchez🇨🇭 · Natalie Jachowicz🇧🇪 · Kajetan Niewczas🇧🇪 · Ashish Kumar Jha🇧🇪 · Alexis Nikolakopoulos🇺🇸
Modern neutrino-nucleus cross section predictions need to incorporate sophisticated nuclear models to achieve greater predictive precision. However, the computational complexity of these advanced models often limits their practicality for experimental analyses. To address this challenge, we introduce a new Monte Carlo method utilizing Normalizing Flows to generate surrogate cross sections that closely approximate those of the original model while significantly reducing computational overhead. As a case study, we built a Monte Carlo event generator for the neutrino-nucleus cross section model developed by the Ghent group. This model employs a Hartree-Fock procedure to establish a quantum mechanical framework in which both the bound and scattering nucleon states are solutions to the mean-field nuclear potential. The surrogate cross sections generated by our method demonstrate excellent accuracy with a relative effective sample size of more than $98.4%$ , providing a computationally efficient alternative to traditional Monte Carlo sampling methods for differential cross sections.
Comments:
Submitted to Physics Review D
Subjects:
High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
arXiv:
2502.14452 [pdf]
PRD(2025)·9 citations
08
[Submitted on 20 Feb 2025] (cross-list from astro-ph.HE)
Long-Term Multidimensional Models of Core-Collapse Supernovae: Progress and Challenges
H.-Thomas Janka (MPI Astrophysics, Garching)🇩🇪
Self-consistent, multidimensional core-collapse supernova (SN) simulations, especially in 3D, have achieved tremendous progress over the past 10 years. They are now able to follow the entire evolution from core collapse through bounce, neutrino-triggered shock revival, shock breakout at the stellar surface to the electromagnetic SN outburst and the subsequent SN remnant phase. Thus they provide general support for the neutrino-driven explosion mechanism by reproducing observed SN energies, neutron-star (NS) kicks, and diagnostically relevant radioactive isotope yields; they allow to predict neutrino and gravitational-wave signals for many seconds of proto-NS cooling; they confirm correlations between explosion and progenitor or remnant properties already expected from previous spherically symmetric (1D) and 2D models; and they carve out various scenarios for stellar-mass black-hole (BH) formation. Despite these successes it is currently unclear which stars explode or form BHs, because different modeling approaches disagree and suggest the possible importance of the 3D nature of the progenitors and of magnetic fields. The role of neutrino flavor conversion in SN cores still needs to be better understood, the nuclear equation of state including potential phase transitions implies major uncertainties, the SN 1987A neutrino measurements raise new puzzles, and tracing a possible correlation of NS spins and kicks requires still more refined SN simulations.
Comments:
40 pages, 8 figures; minor revisions due to referee comments; Annual Review of Nuclear and Particle Science 75, 425 (2025), article DOI: https://doi.org/10.1146/annurev-nucl-121423-100945; errors in Fig.8d corrected, new version consistent with arXiv:2602.02651
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2502.14836 [pdf]
Ann.Rev.Nucl.Part.Sci.(2025)·103 citations

Affiliations

first authorsco-authorsvia INSPIRE