Nuclear Theory·nucl-th

Friday·February 25, 2022

6 papers—3 primary·3 cross-listed

01
Ab initio informed evaluation of the radiative capture of protons on $^{7}$ Be
Konstantinos Kravvaris🇺🇸 · Petr Navrátil🇨🇦 · Sofia Quaglioni🇺🇸 · Chloë Hebborn🇺🇸 · Guillaume Hupin🇫🇷
The radiative capture of protons by $^{7}$ Be, which is the source of $^{8}$ B that $β$ -decays emitting the majority of solar neutrinos measured on earth, has not yet been measured at astrophysically relevant energies. The recommended value for its zero-energy S-factor, $S_{17}$ (0) = 20.8 $\pm$ (0.7)exp $\pm$ (1.4)theory eV $\cdot$ b, relies on theoretical extrapolations from higher-energy measurements, a process that leads to significant uncertainty. We performed a set of first-principle (or, ab initio) calculations of the $^{7}$ Be( $p$ , $γ$ ) $^{8}$ B reaction to provide an independent prediction of the low-energy S-factor with quantified uncertainties. We demonstrate underlying features in the predicted S-factor allowing the combination of theoretical calculations and measurements to produce an evaluated S-factor of $S_{17}$ (0) = 19.8 $\pm$ 0.3 eV $\cdot$ b. We expect the calculations and uncertainty quantification process described here to set a new standard for the evaluation of light-ion astrophysical reactions.
nucl-thnucl-exPLB(2023)·32 citations
02
Deep learning on nuclear mass and $α$ decay half-lives
Chen-Qi Li · Chao-Nan Tong · Hong-Jing Du · Long-Gang Pang
Ab-initio calculations of nuclear masses, the binding energy and the $α$ decay half-lives are intractable for heavy nucleus, because of the curse of dimensionality in many body quantum simulations as proton number( $N$ ) and neutron number( $Z$ ) grow. We take advantage of the powerful non-linear transformation and feature representation ability of deep neural network(DNN) to predict the nuclear masses and $α$ decay half-lives. For nuclear binding energy prediction problem we achieve standard deviation $σ = 0.263$ MeV on 10-fold cross validation on 2149 nuclei. Word-vectors which are high dimensional representation of nuclei from the hidden layers of mass-regression DNN help us to calculate $α$ decay half-lives. For this task, we get $σ = 0.797$ on 100 times 10-fold cross validation on 350 nuclei on $l o g_{10} T_{1/2}$ and $σ = 0.731$ on 486 nuclei. We also find physical a priori such as shell structure, magic numbers and augmented inputs inspired by Finite Range Droplet Model are important for this small data regression task.
nucl-thPRC(2022)·49 citations
03
Delta-resonances and hyperons in proto-neutron stars and merger remnants
Armen Sedrakian🇩🇪 · Arus Harutyunyan🇦🇲
The equation of state (EoS) and composition of dense and hot $Δ$ -resonance admixed hypernuclear matter is studied under conditions that are characteristic of neutron star binary merger remnants and supernovas. The cold, neutrino free regime is also considered as a reference for the astrophysical constraints on the EoS of dense matter. Our formalism uses the covariant density functional (CDF) theory successfully adapted to include the full $J^{P} = 1/ 2^{+}$ baryon octet and non-strange members of $J^{P} = 3/ 2^{+}$ decouplet with density-dependent couplings that have been suitably adjusted to the existing laboratory and astrophysical data. The effect of $Δ$ -resonances at finite temperatures is to soften the EoS of hypernuclear matter at intermediate densities and stiffen it at high densities. At low temperatures, the heavy baryons $Λ$ , $Δ^{-}$ , $Ξ^{-}$ , $Ξ^{0}$ and $Δ^{0}$ appear in the given order if the $Δ$ -meson couplings are close to those for the nucleon-meson couplings. As is the case for hyperons, the thresholds of $Δ$ -resonances move to lower densities with the increase of temperature indicating a significant fraction of $Δ$ 's in the low-density subnuclear regime. We find that the $Δ$ -resonances comprise a significant fraction of baryonic matter, of the order of $10%$ at temperatures of the order of several tens of MeV in the neutrino-trapped regime and, thus, may affect the supernova and binary neutron star dynamics by providing, for example, a new source for neutrino opacity or a new channel for bulk viscosity via the direct Urca processes. The mass-radius relation of isentropic static, spherically symmetric hot compact stars is discussed.
nucl-thastro-ph.HEastro-ph.SREPJA(2022)·41 citations

Affiliations

first authorsco-authorsvia INSPIRE

Ab initio informed evaluation of the radiative capture of protons on 7Be

Deep learning on nuclear mass and α decay half-lives

Delta-resonances and hyperons in proto-neutron stars and merger remnants

Affiliations

Ab initio informed evaluation of the radiative capture of protons on $^{7}$ Be

Deep learning on nuclear mass and $α$ decay half-lives