Nuclear Theory·nucl-th

Wednesday·November 25, 2020

9 papers—5 primary·4 cross-listed

01
[Submitted on 23 Nov 2020]
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.
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Theory (hep-th)
arXiv:
2011.11686 [pdf]
Astron.Nachr.(2021)·3 citations
02
[Submitted on 23 Nov 2020]
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)).
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2011.11687 [pdf]
PRC(2021)·23 citations
03
[Submitted on 24 Nov 2020]
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.
Comments:
6 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2011.11943 [pdf]
PRC(2021)·13 citations
04
[Submitted on 24 Nov 2020]
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.
Comments:
19 pages, 3 figures, 87 equations
Subjects:
Nuclear Theory (nucl-th); Statistical Mechanics (cond-mat.stat-mech)
arXiv:
2011.12128 [pdf]
J.Phys.G(2021)·3 citations
05
[Submitted on 23 Nov 2020]
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.
Comments:
arXiv admin note: text overlap with arXiv:2010.02450
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2011.12235 [pdf]
2 citations
06
[Submitted on 24 Nov 2020] (cross-list from astro-ph.HE)
Astromers in the radioactive decay of r-process nuclei
G. Wendell Misch · T. M. Sprouse · M. R. Mumpower
We study the impact of astrophysically relevant nuclear isomers (astromers) in the context of the rapid neutron capture process (r-process) nucleosynthesis. We compute thermally mediated transition rates between long-lived isomers and the corresponding ground states in neutron-rich nuclei. We calculate the temperature-dependent beta-decay feeding factors which represent the fraction of material going to each of the isomer and ground state daughter species from the beta-decay parent species. We simulate nucleosynthesis by including as separate species nuclear excited states with measured terrestrial half-lives greater than 100 microseconds. We find a variety of isomers throughout the chart of nuclides are populated, and we identify those most likely to be influential. We comment on the capacity of isomer production to alter radioactive heating in an r-process environment.
Comments:
8 pages, 3 figures, 1 table
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2011.11889 [pdf]
ApJL(2021)·38 citations
07
[Submitted on 24 Nov 2020] (cross-list from astro-ph.HE)
$R$ -mode Stability of GW190814's Secondary Component as a Supermassive and Superfast Pulsar
Xia Zhou · Ang Li · Bao-An Li
The nature of GW190814's secondary component $m_{2}$ of mass $(2.50 - 2.67) M_{⊙}$ in the mass gap between the currently known maximum mass of neutron stars and the minimum mass of black holes is currently under hot debate. Among the many possibilities proposed in the literature, the $m_{2}$ was suggested as a superfast pulsar while its r-mode stability against the run-away gravitational radiation through the Chandrasekhar-Friedman-Schutz mechanism is still unknown. Using those fulfilling all currently known astrophysical and nuclear physics constraints among a sample of 33 unified equation of states (EOSs) constructed previously by Fortin {\it et al.} (2016) using the same nuclear interactions from the crust to the core consistently, we compare the minimum frequency required for the $m_{2}$ to rotationally sustain a mass higher than $2.50 M_{⊙}$ with the critical frequency above which the r-mode instability occurs. We use two extreme damping models assuming the crust is either perfectly rigid or elastic. Using the stability of 19 observed low-mass x-ray binaries as an indication that the rigid crust damping of the r-mode dominates within the models studied, we find that the $m_{2}$ is r-mode stable while rotating with a frequency higher than 870.2 Hz (0.744 times its Kepler frequency of 1169.6 Hz) as long as its temperate is lower than about $3.9 \times 1 0^{7} K$ , further supporting the proposal that GW190814's secondary component is a supermassive and superfast pulsar.
Comments:
9 pages, 5 figures, 1 table, version accepted for publication in ApJ
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
2011.11934 [pdf]
ApJ(2021)·34 citations
08
[Submitted on 24 Nov 2020] (cross-list from hep-lat)
Conundrums at Finite Density
Rajiv V. Gavai🇩🇪
Extending the successes of lattice quantum chromodynamics(QCD) at zero as well as nonzero temperatures to nonzero density is extremely desirable in view of the quest for the QCD phase diagram both theoretically and experimentally. It turns out though to give rise to some conundrums whose resolution may assist progress in this exciting but difficult area, and should therefore be sought actively.
Comments:
11 pages, 6 figures, To appear in the proceeding of the international conference on "Criticality in QCD and the Hadron Resonance Gas", 29-31 July 2020, Wroclaw, Poland
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2011.11999 [pdf]
Acta Phys.Polon.Supp.(2021)·0 citations
09
[Submitted on 24 Nov 2020] (cross-list from hep-lat)
Scale setting the Möbius Domain Wall Fermion on gradient-flowed HISQ action using the omega baryon mass and the gradient-flow scales $t_{0}$ and $w_{0}$
Nolan Miller🇺🇸 · Logan C Carpenter🇺🇸 · Evan Berkowitz🇺🇸 · Chia Cheng Chang🇯🇵 · Ben Hörz🇺🇸 · Dean Howarth🇺🇸 · Henry Monge-Camacho🇨🇷 · Enrico Rinaldi🇯🇵 · David A. Brantley🇺🇸 · Christopher Körber🇺🇸 · Chris Bouchard🇬🇧 · M.A. Clark🇺🇸 and 5 other authors
We report on a sub-percent scale determination using the omega baryon mass and gradient-flow methods. The calculations are performed on 22 ensembles of $N_{f} = 2 + 1 + 1$ highly improved, rooted staggered sea-quark configurations generated by the MILC and CalLat Collaborations. The valence quark action used is Möbius Domain-Wall fermions solved on these configurations after a gradient-flow smearing is applied with a flowtime of $t_{gf} = 1$ in lattice units. The ensembles span four lattice spacings in the range $0.06 ≲ a ≲ 0.15$ fm, six pion masses in the range $130 ≲ m_{π} ≲ 400$ MeV and multiple lattice volumes. On each ensemble, the gradient-flow scales $t_{0} / a^{2}$ and $w_{0} / a$ and the omega baryon mass $a m_{Ω}$ are computed. The dimensionless product of these quantities is then extrapolated to the continuum and infinite volume limits and interpolated to the physical light, strange and charm quark mass point in the isospin limit, resulting in the determination of $t_{0} = 0.1422 (14)$ fm and $w_{0} = 0.1709 (11)$ fm with all sources of statistical and systematic uncertainty accounted for. The dominant uncertainty in this result is the stochastic uncertainty, providing a clear path for a few-per-mille uncertainty, as recently obtained by the Budapest-Marseille-Wuppertal Collaboration.
Comments:
v3: Published version; v2: Added determination of t_0 as well as w_0; v1: 13 pages plus appendices. The correlation function data, mass results and analysis code accompanying this publication can be found at this github repository: https://github.com/callat-qcd/project_scale_setting_mdwf_hisq
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2011.12166 [pdf]
PRD(2021)·40 citations

Affiliations

first authorsco-authorsvia INSPIRE