Supernova neutrino process and sensitivity to neutrino temperatures

Some rare isotopes are produced by neutrino-induced reactions in supernova (SN) explosions (v-process). The isotope ⁹²Nb decays to ⁹²Zr with a half-life of 3.47 × 10⁷ years. Although this isotope does not exist in the present solar system, the initial abundance ratio for ⁹²Nb/⁹³Nb at the time of solar system formation (SSF) have been measured in primitive meteorites. The astrophysical origin of ⁹²Nb, however, has remained unknown. The SN v-process origin for ⁹²Nb has been proposed and the SN calculation has demonstrated the v-process origin of ⁹²Nb. The abundances of ν-isotopes depend on neutrino temperatures. In the calculation, the average energies of kT = 3.2, 4.0, 6.0 MeV for the electron neutrino, anti-electron neutrino, and the other neutrinos (v_μ and v_τ), respectively, were used. The observed ratio of ⁹²Nb/⁹³Nb ∼ 10-⁵ can be explained by the v-process.