Nuclear Theory·nucl-th

Monday·April 24, 2023

7 papers—4 primary·3 cross-listed

01
Executive Summary of the Topical Program: Nuclear Isomers in the Era of FRIB
G. W. Misch · M. R. Mumpower · F. G. Kondev · S. T. Marley · S. Almaraz-Calderon · M. Brodeur · B. A. Brown · M. P. Carpenter · J. J. Carroll · C. J. Chiara · K. A. Chipps · B. P. Crider and 20 other authors
We report on the Facility for Rare Isotope Beams (FRIB) Theory Alliance topical program "Nuclear Isomers in the Era of FRIB". We outline the many ways isomers influence and contribute to nuclear science and technology, especially in the four FRIB pillars: properties of rare isotopes, nuclear astrophysics, fundamental symmetries, and applications for the nation and society. We conclude with a resolution stating our recommendation that the nuclear physics community actively pursue isomer research. A white paper is forthcoming.
nucl-thnucl-ex1 citation
02
Quasiparticle resonance in decay spectrum of unbound nuclei near neutron drip-line
Yoshihiko Kobayashi · Masayuki Matsuo
Background: The pairing correlation in weakly bound nuclei causes a mixing among bound and unbound configurations. A remarkable consequence is emergence of the quasiparticle resonance, which has been predicted with the coordinate space Hartree-Fock-Bogoliubov (HFB) theory, but not yet observed experimentally. Purpose: We discuss possible observation of quasiparticle resonances in decay spectrum of unbound nuclei near the neutron drip-line. We deal with an example of unbound nucleus $^{21}$ C which disintegrates to $^{20}$ C and a neutron. Method: We describe a scattering state consisting of $^{20}$ C and a neutron in the framework of the HFB formalism. We assume that a nucleon knockout reaction produces a doorway state of the decay, and we evaluate the decay spectrum by taking an overlap of the doorway state and the scattering state of $^{20} C + n$ . A numerical calculation was performed with the Woods-Saxon potential and a density-dependent effective pairing interaction. Results: We show that the quasiparticle resonance appears as low-lying peaks in the decay spectrum of $^{21}$ C. They originate from the weakly bound single-neutron orbits $2 s_{1/2}$ and $1 d_{5/2}$ , but emerge as unbound resonant quasiparticle states under the influence of the neutron pairing correlation. The resonance energy and the width of the calculated quasiparticle resonances are consistent with an experimental observation whereas they are sensitive to the neutron pairing correlation. Conclusion: The results suggest that nucleon knockout reactions populating the unbound nucleus $^{21} C$ provide realistic opportunity of experimentally observing the quasiparticle resonance and of disclosing the pairing correlation in neutron-rich nuclei.
nucl-thnucl-exPRC(2023)·1 citation
03
Moments of inertia in light deformed nuclei: pairing and mean-field impacts
V.O. Nesterenko · M.A. Mardyban · P.-G. Reinhard · A. Repko · J. Kvasil
The dependence of the moment of inertia $J$ on the pairing and axial quadrupole deformation $β$ in $^{24}$ Mg and $^{20}$ Ne was investigated. The study is based on quadrupole-constrained calculations with three cranking approaches for $J$ (Inglis-Belyaev, Thouless-Valatin, adiabatic time-dependent Hartree-Fock) and a representative set of Skyrme forces (SVbas, SkM*, SLy6). At variance with macroscopic collective models, the calculations predict the specific regime $d J / d β < 0$ at $β \geq 0.5$ ( $^{24}$ Mg) and $β \geq 0.6$ ( $^{20}$ Ne), where the pairing breaks down. This regime is explained by two effects: full break up of the pairing and specific evolution of a {\it single} dominant particle-hole (1ph) configuration with $β$ . The analysis of experimental data for the ground-state rotational bands in $^{24}$ Mg and $^{20}$ Ne shows that such regime is possible at low spins.
nucl-thnucl-exIJMPE(2024)·1 citation
04
$Λ$ and $Λ$ Freeze-Out Distributions and Global Polarizations in Au+Au Collisions
Nikita Tsegelnik (JINR)🇷🇺 · Evgeni Kolomeitsev (JINR, Matej Bel University)🇷🇺 · Vadym Voronyuk (JINR)🇷🇺
The gold--gold collisions at $s_{N N} = 7.7$ and $11.5$ GeV are simulated within the PHSD transport model. In each collision event, the spectator nucleons are separated and the fluidization procedure for the participants is performed. The local velocities are determined in the Landau frame and the kinematic and thermal vorticity fields are evaluated. We analyze the thermodynamic properties of the cells where $Λ$ s and $Λ$ s were born or had their last interaction. Such cells contribute to the formation of the observed global polarization of hyperons induced by the thermal vorticity of the medium. The $Λ$ polarization signal is found to be mainly determined by hot, dense, and highly vortical cells at the earlier stage of the collision, whereas the $Λ$ polarization signal is accumulated over the longer time and includes cells with lower vorticity. The calculated global polarizations for both $Λ$ s and $Λ$ s agree well with the experimental finding by the STAR collaboration at energy $s_{N N} = 11.5$ GeV. For collisions at $s_{N N} = 7.7$ GeV, we can reproduce the STAR data for $Λ$ hyperons, but significantly underpredict the observed global polarization of $Λ$ . Furthermore, we consider the centrality dependence of the hyperon polarization in collisions at 7.7GeV. It increases with an increase of centrality, reaches a maximum at 65--75%, and then starts decreasing rapidly for peripheral collisions.
nucl-thnucl-exParticles(2023)·5 citations
05
Effects of clustered nuclear geometry on the anisotropic flow in O-O collisions at the LHC within a multiphase transport model framework
Debadatta Behera🇮🇳 · Suraj Prasad🇮🇳 · Neelkamal Mallick🇮🇳 · Raghunath Sahoo🇮🇳
To understand the true origin of flowlike signatures and applicability of hydrodynamics in small collision systems, effects of soft QCD dynamics, the sensitivity of jetlike correlations, and nonequilibrium effects, efforts are being made to perform \textit{p}-O and O-O collisions at the LHC and RHIC energies. It is equally interesting to look into the possible signatures of an $α$ -clustered nuclear geometry in $^{16}$ O- $^{16}$ O collisions by studying the initial-state effects on the final-state observables. In this work, within a multiphase transport model, we implement an $α$ -cluster tetrahedral density profile in the oxygen nucleus along with the default Woods-Saxon density profile. We study the eccentricity ( $ϵ_{2}$ ), triangularity ( $ϵ_{3}$ ), normalized symmetric cumulants [NSC(2,3)], elliptic flow ( $v_{2}$ ), and triangular flow ( $v_{3}$ ) in $^{16}$ O- $^{16}$ O collisions at $s_{NN} = 7$ TeV. The constituent quark number scaling of the elliptic flow is also reported. For the most central collisions, enhanced effects in $⟨ ϵ_{3} ⟩ / ⟨ ϵ_{2} ⟩$ and $⟨ v_{3} ⟩ / ⟨ v_{2} ⟩$ with a negative value of NSC(2,3), and an away-side broadening in the two-particle azimuthal correlation function [ $C (Δ ϕ)$ ] of the identified particles are observed in the presence of an $α$ -clustered geometry.
↳ hep-phhep-exhep-thnucl-ex+1PRD(2023)·28 citations
06
Pion screening mass at finite chemical potential
Rishabh Thakkar🇮🇳 · Prasad Hegde🇮🇳
We present a method to compute the responses of meson screening masses to the chemical potential by Taylor expanding the correlator using lattice QCD simulation. We start by comparing the free theory lattice results with the analytical expression. Then, using symmetry arguments, we obtain an expression for the correlator in a series of the chemical potential at finite temperature. Using this, we obtain the lowest order correction to the screening mass at a finite chemical potential for temperatures around 2.5 GeV. Our lattice analysis is limited to isoscalar chemical potential for the pseudoscalar channel. The calculations were performed using (2+1)-flavors of the Highly Improved Staggered Quark (HISQ/tree) action, with the ratio of the strange quark mass to the light quark mass $m_{s} / m_{ℓ} = 20$ corresponding to pion masses of 160 MeV.
↳ hep-lathep-phnucl-exnucl-thJHEP(2023)·3 citations
07
Multi-skyrmion states in the Skyrme model with false vaccum potential
Jun-Shuai Wang🇨🇳 · Yong-Liang Ma🇨🇳
We study the multi-skyrmion states using a Skyrme model with false vacuum potential upto baryon number $B = 8$ using the product ansatz. It is found that, both the false vacuum potential and true vacuum potential can yield cluster structure of the multi-skyrmion states. The effect of the explicit chiral breaking on the masses and the contour surfaces of the baryon number density of the multi-skyrmion states are analyzed.
↳ hep-phhep-thnucl-thCPC(2023)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Executive Summary of the Topical Program: Nuclear Isomers in the Era of FRIB

Quasiparticle resonance in decay spectrum of unbound nuclei near neutron drip-line

Moments of inertia in light deformed nuclei: pairing and mean-field impacts

Λ and Λ Freeze-Out Distributions and Global Polarizations in Au+Au Collisions

Effects of clustered nuclear geometry on the anisotropic flow in O-O collisions at the LHC within a multiphase transport model framework

Pion screening mass at finite chemical potential

Multi-skyrmion states in the Skyrme model with false vaccum potential

Affiliations

$Λ$ and $Λ$ Freeze-Out Distributions and Global Polarizations in Au+Au Collisions