Neutrino Oscillation Effects on Supernova Light‐Element Synthesis

Abstract

Neutrino oscillations affect light-element synthesis through the -process in supernova explosions. The 7 Li and 11 B yields produced in a supernova explosion of a 16.2 M star model increase by factors of 1.9 and 1.3 in the case of the large mixing angle solution with a normal mass hierarchy and sin 2 2 13 k 2 ; 10 À3 compared with those without the oscillations. In the case of an inverted mass hierarchy or a nonadiabatic 1-3 mixing resonance, the increment of their yields is much smaller. Neutrino oscillations raise the reaction rates of charged-current -process reactions in the region outside oxygen-rich layers. The number ratio of 7 Li/ 11 B could be a tracer of a normal mass hierarchy and a relatively large 13 , still satisfying sin 2 2 13 0:1, through future precise observations in stars having strong supernova components.

Neutrino induced reactions forν-process nucleosynthesis of92Nb and98Tc

“…Incident ν(ν) energies emitted in SN explosions [1,4] are expected to be in the energy range of a few MeV to tens of MeV because the ν(ν) energy spectra emitted from the protoneutron star approximately follow a Fermi-Dirac distribution given by a temperature T and a chemical potential α [4,41]. Therefore, the averaged temperature-dependent cross sections can be deduced from an integral over a Fermi-Dirac ν-distribution,…”

“…N is a normalization factor given by dE ν f (E ν )Br. To study the nucleosynthesis [19] or ν-oscillations [4] during a SN explosion, one must specify a realistic temperature and chemical potential for each neutrino species. For our purposes, we adopt T = 3.2, 5.0 and 6.0 MeV for ν e ,ν e and ν µ,τ (ν µ,τ ), respectively, and we set α = 0 [4,19].…”

“…This process has been proposed as the origin of some rare isotopes of light and heavy elements [1]. The cosmic abundances of these nuclei could thus be valuable tools for studying neutrino spectra from SNe [2,3], and for constraining neutrino oscillations and/or other ν-physics parameters [4].…”

THE NEW DETECTIONS OF7Li/6Li ISOTOPIC RATIO IN THE INTERSTELLAR MEDIA

“…However,7 Li has at least three different stellar production sites in addition to the GCR-ISM interactions. These are ν-induced nucleosynthesis in He-and C-layers of Type II supernova (SN) explosion (ν-process; Woosley et al 1990;Woosley & Weaver 1995;Yoshida et al 2006aYoshida et al , 2006b), nova nucleosynthesis (José et al 2003) and nucleosynthesis in asymptotic giant branch (AGB) stars (Forestini & Charbonnel 1997). These production sources have different intensities and efficiencies which depend on the star-formation rate and on the stellar-mass versus gasmass fraction as a function of Galactocentric distance, R G .…”

Can Supernova Neutrino Nucleosynthesis Constrain Neutrino Oscillation Parameters?

“…The resulting large neutrino irradiation of the stellar layers above the PNS induces significant modifications of the isotopic abundance patterns, which is referred to as the ν-process. This process plays an important role for the production of, amongst several, the light elements 7 Li and 11 B [2,3,4]. On the other hand, it has been shown that the neutrinos change their flavors in the O/C and He-rich layers and that this flavor change strongly depends on the mass hierarchy and the mixing angle θ 13 (e.g., [5]).…”