Neutrino Nucleosynthesis of radioactive nuclei in supernovae

Abstract

We study the neutrino-induced production of nuclides in explosive supernova nucleosynthesis for progenitor stars with solar metallicity and initial main sequence masses between 15 M${}_{\odot }$ and 40 M${}_{\odot }$. We improve previous investigations i) by using a global set of partial differential cross sections for neutrino-induced charged- and neutral-current reactions on nuclei with charge numbers $Z<76$ and ii) by considering modern supernova neutrino spectra which have substantially lower average energies compared to those previously adopted in neutrino nucleosynthesis studies. We confirm the production of ${}^7$Li, ${}^{11}$B, ${}^{138}$La, and ${}^{180}$Ta by neutrino nucleosynthesis, albeit at slightly smaller abundances due to the changed neutrino spectra. We find that for stars with a mass smaller than 20 M${}_{\odot }$, ${}^{19}$F is produced mainly by explosive nucleosynthesis while for higher mass stars it is produced by the $\hat{I}½$ process. We also find that neutrino-induced reactions, either directly or indirectly by providing an enhanced abundance of light particles, noticeably contribute to the production of the radioactive nuclides ${}^{22}$Na and ${}^{26}$Al. Both nuclei are prime candidates for gamma-ray astronomy. Other prime targets, ${}^{44}$Ti and ${}^{60}$Fe, however, are insignificantly produced by neutrino-induced reactions. We also find a large increase in the production of the long-lived nuclei ${}^{92}$Nb and ${}^{98}$Tc due to charged-current neutrino capture.

6 pages, 2 figures, 2 tables