Neutrino Spectra from Nuclear Weak Interactions in $sd$-Shell Nuclei Under Astrophysical Conditions

TL;DR

This paper provides detailed shell model calculations of neutrino spectra from 70 sd-shell nuclei under astrophysical conditions, including excited states, for the first time in tabular form, relevant for pre-collapse massive stars.

Contribution

It introduces comprehensive neutrino energy spectra tables for sd-shell nuclei considering excited states and neutral current deexcitation, using an advanced shell model approach for astrophysical applications.

Findings

Neutrino spectra tabulated for 70 sd-shell nuclei across temperature-density grid.

Inclusion of nuclear excited states and neutral current deexcitation channels.

Use of modified Brink-Axel hypothesis for high-temperature nuclear state calculations.

Abstract

We present shell model calculations of nuclear neutrino energy spectra for 70 $sd$-shell nuclei over the mass number range $A=21-35$. Our calculations include nuclear excited states as appropriate for the hot and dense conditions characteristic of pre-collapse massive stars. We consider neutrinos produced by charged lepton captures and decays and, for the first time in tabular form, neutral current nuclear deexcitation, providing neutrino energy spectra on the Fuller-Fowler-Newman temperature-density grid for these interaction channels for each nucleus. We use the full $sd$-shell model space to compute initial nuclear states up to 20 MeV excitation with transitions to final states up to 35-40 MeV, employing a modification of the Brink-Axel hypothesis to handle high temperature population factors and the nuclear partition functions.