Nuclear Theory·nucl-th

Wednesday·March 2, 2022

6 papers—3 primary·3 cross-listed

01
[Submitted on 28 Feb 2022]
The first large-scale shell-model calculation of the two-neutrino double beta decay of $^{76}$ Ge to the excited states in $^{76}$ Se
Joel Kostensalo · Jouni Suhonen · Kai Zuber
Large-scale shell-model calculations were carried out for the half-lives and branching ratios of the $2 ν β β$ decay of $^{76}$ Ge to the ground state and the lowest three excited states $2_{1}^{+}$ , $0_{2}^{+}$ and $2_{2}^{+}$ in $^{76}$ Se. In total, the wave functions of more than 10,000 intermediate $1^{+}$ states in $^{76}$ As were calculated in a three-step procedure allowing an efficient use of the available computer resources. In the first step, 250 lowest states, below some 5 MeV of excitation energy, were calculated without truncations within a full major shell $0 f_{5/2} - 1 p - 0 g_{9/2}$ for both protons and neutrons. The wave functions of the rest of the states, up to some 30 MeV, were computed in two more steps by introducing two consecutive stages of truncation. The computed magnitudes of the $2 ν β β$ nuclear matrix elements (including the value of the axial-vector coupling $g_{A}$ ), $∣ M_{2 ν} ∣ g_{A}^{2}$ , converged to the values 0.168 $g_{A}^{2}$ , $1.2 \times 1 0^{- 3}$ $g_{A}^{2}$ , 0.121 $g_{A}^{2}$ , and $3.1 \times 1 0^{- 3}$ $g_{A}^{2}$ for the $0_{g.s.}^{+}$ , $2_{1}^{+}$ , $0_{2}^{+}$ , and $2_{2}^{+}$ states, respectively. Using up-to-date phase-space integrals, the corresponding branching ratios were derived to be 99.926\%, 4.4 $\times 1 0^{- 5}$ \%, 0.074\% and 2.5 $\times 1 0^{- 7}$ \%. The experimental half-life $(1.926 \pm 0.094) \times 1 0^{21}$ yr of the ground-state transition was used to derive the value $g_{A} = 0.80 \pm 0.01$ for the axial-vector coupling, which is consistent with other shell-model calculations suggesting a quenched value of $g_{A}$ . Using this value of $g_{A}$ , predictions for the transition half-lives were derived.
Comments:
10 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2203.00109 [pdf]
PLB(2022)·15 citations
02
[Submitted on 28 Feb 2022]
Transport coefficients of the quark-gluon plasma at the critical point and across the first-order line
Joaquin Grefa🇺🇸 · Mauricio Hippert🇺🇸 · Jorge Noronha🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸 · Israel Portillo🇺🇸 · Claudia Ratti🇺🇸 · Romulo Rougemont🇺🇸
A bottom-up Einstein-Maxwell-Dilaton holographic model is used to compute, for the first time, the behavior of several transport coefficients of the hot and baryon-rich strongly coupled quark-gluon plasma at the critical point and also across the first-order phase transition line in the phase diagram. The observables under study are of the shear and bulk viscosities, baryon diffusion, thermal conductivity, the jet quenching parameter $q^$ , as well as the heavy-quark drag force and Langevin diffusion coefficients. These calculations provide a phenomenologically promising estimate for these coefficients, given that our model quantitatively reproduces lattice QCD thermodynamics results, both at zero and finite baryon density, besides naturally incorporating the nearly-perfect fluidity of the quark-gluon plasma. We find that the diffusion of baryon charge, and also the shear and bulk viscosities, are suppressed with increasing baryon density, indicating that the medium becomes even closer to perfect fluidity at large densities. On the other hand, the jet quenching parameter and the heavy-quark momentum diffusion are enhanced with increasing density. The observables display a discontinuity gap when crossing the first-order phase transition line, while developing an infinite slope at the critical point. The transition temperatures associated with different transport coefficients differ in the crossover region but are found to converge at the critical point.
Comments:
18 pages, 13 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2203.00139 [pdf]
PRD(2022)·66 citations
03
[Submitted on 1 Mar 2022]
Chiral symmetry restoration and the $Δ$ matter formation in neutron stars
Michał Marczenko🇵🇱 · Krzysztof Redlich🇵🇱 · Chihiro Sasaki🇵🇱
We analyze the effects of chiral symmetry restoration in hadronic matter, including the lowest-lying baryonic resonance $Δ$ based on the parity doublet model. We study the role of $Δ$ and its chiral partner on the equation of state (EoS) of dense matter under neutron star (NS) conditions of $β$ -equilibrium and charge neutrality. We find that the softening of the EoS driven by the early onset of $Δ$ matter due to partial restoration of chiral symmetry allows accommodating the modern multi-messenger astrophysical constraints on the mass, radius, and tidal deformability. The softening above the saturation density is accompanied by subsequent stiffening at high densities. We also find that the matter composition in the NS cores may be different upon variations of the repulsive interactions of $Δ$ baryons in hadronic matter.
Comments:
arXiv admin note: text overlap with arXiv:2110.11056, arXiv:2004.09566
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2203.00269 [pdf]
PRD(2022)·32 citations

Affiliations

first authorsco-authorsvia INSPIRE

The first large-scale shell-model calculation of the two-neutrino double beta decay of 76Ge to the excited states in 76Se

Transport coefficients of the quark-gluon plasma at the critical point and across the first-order line

Chiral symmetry restoration and the Δ matter formation in neutron stars

Affiliations

The first large-scale shell-model calculation of the two-neutrino double beta decay of $^{76}$ Ge to the excited states in $^{76}$ Se

Chiral symmetry restoration and the $Δ$ matter formation in neutron stars