Nuclear Theory·nucl-th

Wednesday·November 25, 2020

9 papers—5 primary·4 cross-listed

01
Deconfinement Phase Transition under Chemical Equilibrium
Veronica Dexheimer🇺🇸 · Krishna Aryal🇺🇸 · Madison Wolf🇺🇸 · Constantinos Constantinou🇮🇹 · Ricardo L. S. Farias🇨🇱
In this work, we investigate how the assumption of chemical equilibrium with leptons affects the deconfinement phase transition to quark matter. This is done within the framework of the Chiral Mean Field model (CMF) allowing for non-zero net strangeness, corresponding to the conditions found in astrophysical scenarios. We build 3-dimensional QCD phase diagrams with temperature, baryon chemical potential, and either charge or isospin fraction or chemical potential to show how the deconfinement region collapses to a line in the special case of chemical equilibrium, such as the one established the interior of cold catalyzed neutron stars.
nucl-thastro-ph.HEastro-ph.SRhep-thAstron.Nachr.(2021)·3 citations
02
A Comprehensive Study of the Three- and Four-Neutron Systems at Low Energies
Michael D. Higgins · Chris H. Greene · Alejandro Kievsky · Michele Viviani
This work presents further analysis of the three- and four-neutron systems in the low energy regime using adiabatic hyperspherical methods. In our previous Phys. Rev. Lett. article (Phys. Rev. Lett. 125, 052501 (2020)), the low-energy behavior of these neutron systems was treated in the adiabatic approximation, neglecting the off-diagonal non-adiabatic couplings. A thorough analysis of the density of states through a multi-channel treatment of the three-and four-neutron scattering near the scattering continuum threshold is performed, showing no evidence of a 4n resonance at low energy. A detailed analysis of the long-range behavior of the lowest few adiabatic hyperspherical potentials shows there is an attractive $ρ^{- 3}$ universal behavior which dominates in the low-energy regime of the multi-channel scattering. This long-range behavior leads to a divergent behavior of the density of state for $E \to 0$ that could account for the low-energy signal observed in the 2016 experiment by Kisamori et al. (Phys. Rev. Lett. 116, 052501 (2016)).
nucl-thPRC(2021)·23 citations
03
Learning the structure of giant resonances from their $γ$ -decay
W. L. Lv · Y. F. Niu · G. Colò
The direct $γ$ -decays of the giant dipole resonance (GDR) and the giant quadrupole resonance (GQR) of $^{208}$ Pb to low-lying states are investigated by means of a microscopic self-consistent model. The model considers effects beyond the linear response approximation. The strong sensitivity of $γ$ -decay to the isospin of the involved states is proven. By comparing their decay widths, a much larger weight of the $3_{1}^{-}$ component in the GQR wave function of $^{208}$ Pb is deduced, with respect to the weight of the $2_{1}^{+}$ component in the GDR wave function. Thus, we have shown that $γ$ -decay is a unique probe of the resonance wave functions, and a testground for nuclear structure models.
nucl-thPRC(2021)·13 citations
04
Alternative Formulation of the Induced Surface and Curvature Tensions Approach
Kyrill A. Bugaev🇺🇦
We develop a novel method to analyze the excluded volume of the multicomponent mixtures of classical hard spheres in the grand canonical ensemble. The method is based on the Laplace-Fourier transform technique and allows one to account for the fluctuations of the particle number density for the induced surface and curvature tensions equation of state. As a result one can go beyond the Van der Waals approximation by obtaining the suppression of the induced surface and curvature tensions coefficients at moderate and high packing fractions. In contrast to the standard induced surface and curvature tensions equation of state the suppression of these coefficients is not an exponential one, but a power-like one. The obtained alternative equation of state is further generalized to account for higher virial coefficients. This result is straightforwardly generalized to the case of quantum statistics.
nucl-thcond-mat.stat-mechJ.Phys.G(2021)·3 citations
05
Neutron skin $r_{skin}^{48}$ determined from reaction cross section of proton+ $^{48}$ Ca scattering
Shingo Tagami · Maya Takechi · Jun Matsui · Tomotsugu Wakasa · Masanobu Yahiro
{\bf Background:} Using the chiral (Kyushu) $g$ -matrix folding model with the densities calculated with GHFB+AMP, we determined $r_{skin}^{208} = 0.25$ fm from the central values of $σ_{R}$ of p+ $^{208}$ Pb scattering in $E_{in} = 40 - 81$ MeV. The high-resolution $E 1$ polarizability experiment ( $E 1$ pE) yields $r_{skin}^{48} (E 1 pE) = 0.14 - 0.20$ fm. The data on $σ_{R}$ are available as a function of $E_{in}$ for $p$ + $^{48}$ Ca scattering. {\bf Aim:} Our aim is to determine $r_{skin}^{48}$ from the central values of $σ_{R}$ for $p$ + $^{48}$ Ca scattering by using the folding model. {\bf Results:} As for $^{48}$ Ca, we determine $r_{n} (E 1 pE) = 3.56$ fm from the central value 0.17fm of $r_{skin}^{48} (E 1 pE)$ and $r_{p} (EXP) = 3.385$ fm of electron scattering, and evaluate $r_{m} (E 1 pE) = 3.485$ fm from the $r_{n} (E 1 pE)$ and the $r_{p} (EXP)$ of electron scattering. The folding model with GHFB+AMP densities reproduces $σ_{R}$ in $23 \leq E_{in} \leq 25.3$ MeV in one- $σ$ level, but slightly overestimates the central values of $σ_{R}$ there. In $23 \leq E_{in} \leq 25.3$ MeV, the small deviation allows us to scale the GHFB+AMP densities to the central values of $r_{p} (EXP)$ and $r_{n} (E 1 pE)$ . The $σ_{R} (E 1 pE)$ obtained with the scaled densities almost reproduce the central values of $σ_{R}$ when $E_{in} = 23 - 25.3$ MeV, so that the $σ_{R} (GHFB + AMP)$ and the $σ_{R} (E 1 pE)$ are in 1- $σ$ of $σ_{R}$ there. In $E_{in} = 23 - 25.3$ MeV, we determine the $r_{m} (EXP)$ from the central values of $σ_{R}$ and take the average for the $r_{m} (EXP)$ . The averaged value is $r_{m} (EXP) = 3.471$ fm. Eventually, we obtain $r_{skin}^{48} (EXP) = 0.146$ fm from $r_{m} (EXP) = 3.471$ fm and $r_{p} (EXP) = 3.385$ fm.
nucl-thnucl-ex2 citations

Affiliations

first authorsco-authorsvia INSPIRE

Deconfinement Phase Transition under Chemical Equilibrium

A Comprehensive Study of the Three- and Four-Neutron Systems at Low Energies

Learning the structure of giant resonances from their γ-decay

Alternative Formulation of the Induced Surface and Curvature Tensions Approach

Neutron skin rskin48​ determined from reaction cross section of proton+48Ca scattering

Affiliations

Learning the structure of giant resonances from their $γ$ -decay

Neutron skin $r_{skin}^{48}$ determined from reaction cross section of proton+ $^{48}$ Ca scattering