Nuclear Theory·nucl-th

Thursday·February 15, 2024

10 papers—2 primary·8 cross-listed

01
Indispensability of cross-shell contributions in neutron resonance spacing
T. Ghosh · Sangeeta · B. Maheshwari · G. Saxena · B. K. Agrawal
Spin and parity dependent nuclear level densities (NLDs) are obtained for configuration interaction shell model using a numerically efficient spectral distribution method. The calculations are performed for $^{24}$ Na, $^{25, 26, 27}$ Mg nuclei using full $s d$ - $p f$ model space that incorporates the cross-shell excitations from $s d$ to $p f$ -shell. The NLDs so obtained are then employed to determine the s-wave neutron resonance spacing (D $_{0}$ ) which is one of the crucial inputs for the predictions of astrophysical reaction rates. Though the considered nuclei are not neutron-rich, the contributions from cross-shell excitations to $p f$ -shell are indispensable to explain the experimental data for D $_{0}$ which otherwise are significantly overestimated.
nucl-thJ.Phys.G(2024)·0 citations
02
Understanding the mirror asymmetry in Gamow-Teller transition rates between $^{28}$ Al( $β^{-}$ ) $^{28 m}$ Si and $^{28}$ P( $β^{+}$ ) $^{28 m}$ Si
L. Xayavong🇰🇷 · N. A. Smirnova🇫🇷 · Y. Lim🇰🇷
The long-standing discrepancy between shell-model and experimental values of the mirror asymmetry in Gamow-Teller transition rates for $^{28}$ Al( $β^{-}$ ) $^{28 m}$ Si and $^{28}$ P( $β^{+}$ ) $^{28 m}$ Si is partially resolved by integrating the $p$ -orbital contribution into the radial mismatch correction term. This approach offers a potential estimate of the radial mismatch-induced core-orbital contribution based on the French-Macfarlane sum rules, avoiding the need for heavy calculations required by the first-principle shell model. Additionally, the isospin-mixing contribution undergoes considerable improvement through scaling the calculated isospin-mixing correction with the experimental energy separation between the lowest two admixed states, in accordance with the result from the two-level model.
nucl-thnucl-exPRC(2024)·2 citations
03
Noble Gas Planetology and the Xenon Clouds of Uranus
Kevin J Zahnle
Noble gases provide tracers of cosmic provenance that are accessible to a future Uranus Atmospheric Probe. Argon and krypton are expected to be well-mixed on Uranus with respect to H $_{2}$ and He, although condensation at the winter pole may be possible. The Ar/H $_{2}$ and Ar/Kr ratios address whether the materials accreted by Uranus resembled the extremely cold materials accreted by Jupiter's atmosphere, or whether they were warmer like comet 67P/Churyumov-Gerasimenko, or whether Uranus is like neither. Xenon condenses as an ice, probably on methane ice, in Uranus's upper troposphere. Condensation may complicate interpretation of Xe/H $_{2}$ , but it also presents an opportunity to collect concentrated xenon samples suitable for measuring isotopes. Solar System Xe tracks three distinct nucleosynthetic xenon reservoirs, one evident in the Sun and in chondritic meteorites, a second in refractory presolar grains, and a third evident in comet 67P/C-G and in Earth's air. The first and third reservoirs appear to have been captured from different clouds of gas. The two gases do not appear to have been well-mixed; moreover, the high $^{129}$ Xe/ $^{132}$ Xe ratio in 67P/C-G implies that the gas was captured before the initial nucleosynthetic complement of $^{129}$ I (15.7 Myr half-life) had decayed. Xenon's isotopic peculiarities, if seen in Uranus, could usefully upset our understanding of planetary origins. Krypton's isotopic anomalies are more subtle and may prove hard to measure. There is a slight chance that neon and helium fractionations can be used to constrain how Uranus acquired its nebular envelope.
↳ astro-ph.EPnucl-thPlanet.Sci.J.(2024)·0 citations
04
Systematic many-fermion Hamiltonian input scheme and spectral calculations on quantum computers
Weijie Du · James P. Vary
We present a novel input scheme for general second-quantized Hamiltonians of relativistic or non-relativistic many-fermion systems. This input scheme incorporates the fermionic anticommutation relations, particle number variations, and respects the symmetries of the Hamiltonian. Based on our input scheme, we propose a hybrid quantum-classical framework for spectral calculations on future quantum hardwares. We provide explicit circuit designs and the associated gate cost. We demonstrate our hybrid framework by solving the low-lying spectra of $^{42}$ Ca and $^{46}$ Ca. Our input scheme provides new pathways to solving the spectra and dynamics of the relativistic and nonrelativistic many-fermion systems via first-principles approaches.
↳ quant-phnucl-thPLB(2025)·14 citations
05
Doubly heavy dibaryons as seen by string theory
Oleg Andreev🇩🇪
We propose the stringy description of the system consisting of two heavy and four light quarks in the case of two light flavors of equal mass. As an application, we consider the three low-lying Born-Oppenheimer potentials as a function of the heavy quark separation. Our analysis shows that the ground state potential is described in terms of both hadro-quarkonia and hadronic molecules. A connected string configuration makes the dominant contribution to the potential of an excited state at small separations, and for separations larger than $0.1 fm$ , it exhibits the diquark-diquark-diquark structure $[Qq] [Qq] [q q]$ . For better understanding the quark organization inside the system, we introduce several critical separations related to the processes of string reconnection, breaking and junction annihilation. We also discuss the simplest string configurations including the five-string junctions and their implications for the system, in particular the emergence of composite quark objects different from diquarks and the process of junction fusion.
↳ hep-phhep-lathep-thnucl-thPRD(2024)·7 citations
06
Thermodynamic properties and phase diagram of quark matter within non-extensive Polyakov chiral SU (3) quark mean field model
Dhananjay Singh🇮🇳 · Arvind Kumar🇮🇳
In the present work, we apply Tsallis non-extensive statistics to study the thermodynamic properties and phase diagram of quark matter in the Polyakov chiral SU(3) quark mean field model. Within this model, the properties of the quark matter are modified through the scalar fields $σ, ζ, δ, χ$ , the vector fields $ω, ρ$ , $ϕ$ , and the Polyakov fields $Φ$ and $Φ ˉ$ at finite temperature and chemical potential. Non-extensive effects have been introduced through a dimensionless parameter $q$ and the results are compared to the extensive case ( $q \to 1$ ). In the non-extensive case, the exponential in the Fermi-Dirac (FD) function is modified to a $q$ -exponential form. The influence of $q$ parameter on the thermodynamic properties: pressure, energy, and entropy density as well as trace anomaly is investigated. The speed of sound and specific heat with non-extensive effects is also studied. Furthermore, the effect of non-extensivity on the deconfinement phase transition as well as the chiral phase transition of $u, d,$ and $s$ quarks is explored. We found that the critical end point (CEP), which defines the point in the $(T - μ)$ phase diagram where the order of the phase transition changes, shifts to a lower value of temperature, $T_{C E P}$ , and a higher value of chemical potential, $μ_{C E P}$ , as the non-extensivity is increased, i.e., $q >$ 1.
↳ hep-phnucl-thCPC(2024)·6 citations
07
Minijet quenching in non-equilibrium quark-gluon plasma
Fabian Zhou🇩🇪 · Jasmine Brewer🇬🇧 · Aleksas Mazeliauskas🇩🇪
We study the energy deposition and thermalisation of high-momentum on-shell partons (minijets) travelling through a non-equilibrium Quark-Gluon Plasma using QCD kinetic theory. For thermal backgrounds, we show that the parton energy first flows to the soft sector by collinear cascade and then isotropises via elastic scatterings. In contrast, the momentum deposition from a minijet reaches the equilibrium distribution directly. For expanding non-equilibrium QGP, we study the time for a minijet perturbation to lose memory of its initial conditions, namely, the hydrodynamisation time. We show that the minijet evolution scales well with the relaxation time $τ_{R} \propto η / s / T (τ)$ , where $T (τ)$ is the effective temperature and $η / s$ is the viscosity over entropy ratio.
↳ hep-phnucl-thJHEP(2024)·19 citations
08
Exploring semi-inclusive two-nucleon emission in neutrino scattering: a factorized approximation approach
V.L. Martinez-Consentino🇪🇸 · J.E. Amaro🇪🇸
The semi-inclusive cross section of two-nucleon emission induced by neutrinos and antineutrinos is computed employing the relativistic mean field model of nuclear matter and the dynamics of meson exchange currents. Within this model we explore a factorization approximation based on the product of an integrated two-hole spectral function and a two-nucleon cross section averaged over hole pairs. We demonstrate that the integrated spectral function of the uncorrelated Fermi gas can be analytically computed, and we derive a simple fully relativistic formula for this function, showcasing its dependency solely on both missing momentum and missing energy. A prescription for the average momenta of the two holes in the factorized two-nucleon cross section is provided, assuming that these momenta are perpendicular to the missing momentum in the center-of-mass system. The validity of the factorized approach is assessed by comparing it with the unfactorized calculation. Our investigation includes the study of the semi-inclusive cross section integrated over the energy of one of the emitted nucleons and the cross section integrated over the emission angles of the two nucleons and the outgoing muon kinematics. A comparison is made with the pure phase-space model and other models from the literature. The results of this analysis offer valuable insights into the influence of the semi-inclusive hadronic tensor on the cross section, providing a deeper understanding of the underlying nuclear processes.
↳ hep-phnucl-thSymmetry(2024)·6 citations
09
Long-Distance Nuclear Matrix Elements for Neutrinoless Double-Beta Decay from Lattice QCD
Zohreh Davoudi🇺🇸 · William Detmold🇺🇸 · Zhenghao Fu🇺🇸 · Anthony V. Grebe🇺🇸 · William Jay🇺🇸 · David Murphy🇺🇸 · Patrick Oare🇺🇸 · Phiala E. Shanahan🇺🇸 · Michael L. Wagman🇺🇸
Neutrinoless double-beta ( $0 ν β β$ ) decay is a heretofore unobserved process which, if observed, would imply that neutrinos are Majorana particles. Interpretations of the stringent experimental constraints on $0 ν β β$ -decay half-lives require calculations of nuclear matrix elements. This work presents the first lattice quantum-chromodynamics (LQCD) calculation of the matrix element for $0 ν β β$ decay in a multi-nucleon system, specifically the $nn \to pp ee$ transition, mediated by a light left-handed Majorana neutrino propagating over nuclear-scale distances. This calculation is performed with quark masses corresponding to a pion mass of $m_{π} = 806$ MeV at a single lattice spacing and volume. The statistically cleaner $Σ^{-} \to Σ^{+} ee$ transition is also computed in order to investigate various systematic uncertainties. The prospects for matching the results of LQCD calculations onto a nuclear effective field theory to determine a leading-order low-energy constant relevant for $0 ν β β$ decay with a light Majorana neutrino are investigated. This work, therefore, sets the stage for future calculations at physical values of the quark masses that, combined with effective field theory and nuclear many-body studies, will provide controlled theoretical inputs to experimental searches of $0 ν β β$ decay.
↳ hep-latnucl-thPRD(2024)·16 citations
10
Anisotropy Scaling Functions in Heavy-Ion Collisions: Insights into the `Ultra-Central Flow Puzzle' and Constraints on Transport Coefficients and Nuclear Deformation
Roy A. Lacey (Department of Chemistry, Stony Brook University, Stony Brook, NY, USA)🇺🇸
Anisotropy scaling functions derived from comprehensive measurements of transverse momentum- and centrality-dependent anisotropy coefficients $v_2(p_T,\text{cent})$ and $v_3(p_T,\text{cent})$ in Pb+Pb collisions at 5.02 and 2.76 TeV, Xe+Xe collisions at 5.44 TeV and Au+Au collisions at 0.2 TeV, offer new insights into the `ultra-central flow puzzle.' These functions integrate diverse measurements into a single curve, clarifying anisotropy attenuation throughout the entire $p_T$ and centrality range. They reveal the influence of initial-state eccentricities ($\varepsilon_{n}$), dimensionless size ($\mathbb{R}$), radial flow, viscous correction to the thermal distribution function ($\delta_f$), the medium's stopping power ($\Hat{q}$), and specific shear viscosity ($\eta/s$) on the observed anisotropies. This analysis not only enhances understanding of transport coefficients but also provides crucial constraints on nuclear deformation.
↳ nucl-exhep-exnucl-thPRC(2024)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE