Nuclear Theory·nucl-th

Friday·January 7, 2022

9 papers—4 primary·5 cross-listed

01
Proto-neutron star evolution with improved charged-current neutrino-nucleon interactions
A Pascal (LUTH (UMR\_8102))🇫🇷 · J Novak (LUTH (UMR\_8102))🇫🇷 · M Oertel (LUTH (UMR\_8102))🇫🇷
We perform simulations of the Kelvin-Helmholtz cooling phase of proto-neutron stars with a new numerical code in spherical symmetry and using the quasi-static approximation. We use for the first time the full set of charged-current neutrino-nucleon reactions, including neutron decay and modified Urca processes, together with the energy-dependent numerical representation for the inclusion of nuclear correlations with random-phase approximation. Moreover, convective motions are taken into account within the mixing-length theory. As we vary the assumptions for computing neutrino-nucleon reaction rates, we show that the dominant effect on the cooling timescale, neutrino signal and composition of the neutrino-driven wind comes from the inclusion of convective motion. Computation of nuclear correlations within the random phase approximation, as compared to mean field approach, has a relatively small impact.
nucl-thastro-ph.HEMNRAS(2022)·63 citations
02
Shell-model study on properties of proton dripline nuclides with Z, N = 30-50 including uncertainty analysis
Boshuai Cai · Guangshang Chen · Cenxi Yuan · Jianjun He
The binding energies and proton separation energies of nuclides with $Z, N = 30 - 50$ are investigated, based on the shell model with an uncertainty analysis through statistical methods. Several formulas are used to obtain the binding energies and proton separation energies according to the shell-model calculations. The non-parametric Bootstrap method is applied to establish an uncertainty decomposition and recomposition framework. Moreover, it is used to estimate the stability of proton(s) emission for each nuclide. Two formulas for calculating the binding energies with a systematic uncertainty of $\sim 0.3$ MeV are proposed, and a reliable extrapolation ability is examined. These binding energy formulas deduce similar forms of respective $S_{p}$ and $S_{2 p}$ energies, which predict the extension of the nuclear boundary of this region. A nice description of the binding energies and proton separation energies is provided. The one- and two-proton separation energies and partial half-lives of proton emitting are predicted, thus showing a new dripline. Besides, there are 30 unstable nuclides predicted to be bound against proton(s)-emission. These nuclear properties will be useful in nuclear astrophysics.
nucl-thCPC(2022)·2 citations
03
Collective expansion in pp collisions using the Tsallis statistics
J.B. Gu🇨🇳 · C.Y. Li🇨🇳 · Q. Wang🇨🇳 · W.C. Zhang🇨🇳 · H. Zheng🇨🇳
We investigate the transverse momentum ( $p_{T}$ ) spectra of identified hadrons in minimum-bias proton-proton (pp) collisions at a centre-of-mass energy ( $s$ ) of 0.9, 2.76, 5.02, 7 and 13 TeV in the framework of Tsallis-blast wave (TBW) model. It is found that the model describes well the particle spectra up to 10 GeV/c. The radial flow ( $⟨ β ⟩$ ) increases with the collision energy. The degrees of non-equilibrium ( $q$ ) and the Tsallis temperature parameter ( $T$ ) show a similar behaviour, but with a much weaker trend. With this dependence of the freeze-out parameters on the collision energy, we evaluate $⟨ β ⟩$ , $T$ and $q$ in pp collisions at $s =$ 8 and 14 TeV and predict the particle spectra at these two energies. Moreover, in order to investigate the multiplicity dependence of the freeze-out parameters, the TBW model is extended to the spectra at different charged-particle multiplicity classes in pp collisions at $s =$ 7 and 13 TeV. It is observed that at both energies the radial flow increases with the multiplicity while the degree of non-equilibrium shows an opposite behaviour, which is similar to that observed in proton-nucleus (pA) and nucleus-nucleus (AA) collisions at the Large Hadron Collider (LHC) energies. However, the Tsallis temperature parameter increases with the multiplicity, which is opposite to the trend in pA and AA collisions. At similar multiplicities, the radial flow in pp collisions is stronger than those in pA and AA collisions, indicating that the size of the colliding system has significant effects on the final state particle dynamics. Finally, we apply an additional flow correction to the Tsallis temperature parameter and find that the doppler-corrected temperature parameter almost scales with the multiplicity in a uniform way, despite the difference in the colliding system and collision energy.
nucl-thhep-phJ.Phys.G(2022)·22 citations
04
Anatomy of octupole correlations in $^{96}$ Zr with a symmetry-restored multidimensionally-constrained covariant density functional theory
Yu-Ting Rong · Xian-Ye Wu · Bing-Nan Lu · Jiang-Ming Yao
A recent analysis based on the STAR measurement in relativistic heavy-ion collision experiments provides evidence of octupole correlation in the ground state of $^{96}$ Zr, the description of which presents a challenge to nuclear structure models. In this work, we perform projection-after-variation calculations for $^{96}$ Zr based on a multidimensionally-constrained relativistic Hartree-Bogoliubov model. Our results show that an octupole deformed shape is favored in energy after symmetry restoration, and this phenomenon cannot be reproduced in the pure mean-field calculations. These complex structures originate from the competition among various shell structures in this mass region. Our results suggest that the allowance of symmetry breaking at the mean-field level and the restoration of broken symmetries are essential elements for understanding the structure of $^{96}$ Zr in density functional theories.
nucl-thnucl-exPLB(2023)·32 citations
05
Hyperons and $Θ_{s}^{+}$ in Holographic QCD
Yizhuang Liu🇵🇱 · Maciej A. Nowak🇵🇱 · Ismail Zahed🇺🇸
We revisit the holographic description of strange baryons in the context of the Sakai-Sugimoto construction, by considering the strange quark mass as heavy. Hyperons are described by a massive $(K, K^{*})$ multiplet, bound to a light-flavor instanton in bulk, much in the spirit of the Callan-Klebanov construction. The modular Hamiltonian maps onto the Landau problem, a charged particle in a 2-dimensional external magnetic field, induced by the bulk Chern-Simons interaction, plus spin-orbit coupling. The ensuing holographic hyperon spectrum compares fairly with the empirical one. The holographic strange pentaquark baryon $Θ_{s}^{+}$ is shown to be unbound.
↳ hep-phnucl-exnucl-thPRD(2022)·5 citations
06
Status of Lattice QCD Determination of Nucleon Form Factors and their Relevance for the Few-GeV Neutrino Program
Aaron S. Meyer🇺🇸 · André Walker-Loud🇺🇸 · Callum Wilkinson🇺🇸
Calculations of neutrino-nucleus cross sections begin with the neutrino-nucleon interaction, making the latter critically important to flagship neutrino oscillation experiments, despite limited measurements with poor statistics. Alternatively, lattice QCD (LQCD) can be used to determine these interactions from the Standard Model with quantifiable theoretical uncertainties. Recent LQCD results of $g_{A}$ are in excellent agreement with data, and results for the (quasi-)elastic nucleon form factors with full uncertainty budgets are expected within a few years. We review the status of the field and LQCD results for the nucleon axial form factor, $F_{A} (Q^{2})$ , a major source of uncertainty in modeling sub-GeV neutrino-nucleon interactions. Results from different LQCD calculations are consistent, but collectively disagree with existing models, with potential implications for current and future neutrino oscillation experiments. We describe a road map to solidify confidence in the LQCD results and discuss future calculations of more complicated processes, important to few-GeV neutrino oscillation experiments.
↳ hep-lathep-exhep-phnucl-ex+1Ann.Rev.Nucl.Part.Sci.(2022)·81 citations
07
Anomalous enhancement of dilepton production as a precursor of color superconductivity
Toru Nishimura🇯🇵 · Masakiyo Kitazawa🇯🇵 · Teiji Kunihiro🇯🇵
We compute the modification of the photon self-energy due to dynamical diquark fluctuations developed near the critical temperature of the color superconductivity through the Aslamasov-Larkin, Maki-Thompson and density of states terms, which are responsible for the paraconductivity in metals at vanishing energy and momentum. It is shown that the rate has a significant enhancement at low invariant-mass region over a rather wide range of temperature in the normal phase. This enhancement is worth exploration in the relativistic heavy-ion collisions, which may thereby reveal the significance of the diquark fluctuations in dense quark matter.
↳ hep-phnucl-exnucl-thPTEP(2022)·18 citations
08
Analyzing transverse momentum spectra by a new method in high-energy collisions
Li-Li Li🇨🇳 · Fu-Hu Liu🇨🇳 · Muhammad Waqas🇨🇳 · Muhammad Ajaz🇵🇰
We analyzed the transverse momentum spectra of positively and negatively charged pions ( $π^{+}$ and $π^{-}$ ), positively and negatively charged kaons ( $K^{+}$ and $K^{-}$ ), protons and antiprotons ( $p$ and $p ˉ$ ), as well as $ϕ$ produced in mid-(pseudo)rapidity region in central nucleus--nucleus (AA) collisions over a center-of-mass energy range from 2.16 to 2760 GeV per nucleon pair. The transverse momentum of the considered particle is regarded as the joint contribution of two participant partons which obey the modified Tsallis-like transverse momentum distribution and have random azimuths in superposition. The calculation of transverse momentum distribution of particles is performed by the Monte Carlo method and compared with the experimental data measured by international collaborations. The excitation functions of effective temperature and other parameters are obtained in the considered energy range. With the increase of collision energy, the effective temperature parameter increases quickly and then slowly. The boundary appears at around 5 GeV, which means the change of reaction mechanism and/or generated matter.
↳ hep-phhep-exnucl-exnucl-thUniverse(2022)·17 citations
09
How well do we know the gluon polarization in the proton?
Y. Zhou🇨🇳 · N. Sato🇺🇸 · W. Melnitchouk🇺🇸
We perform the first simultaneous global QCD analysis of spin-averaged and spin-dependent parton distribution functions (PDFs), including single jet production data from unpolarized and polarized hadron collisions. We critically assess the impact of SU(3) flavor symmetry and PDF positivity assumptions on the quark and gluon helicity PDFs, and find strong bias from these, particularly on the gluon polarization. The simultaneous analysis allows for the first time extraction of individual helicity-aligned and antialigned PDFs with a consistent treatment of uncertainties.
↳ hep-phhep-exnucl-thPRD(2022)·62 citations

Affiliations

first authorsco-authorsvia INSPIRE