Supernova Neutrino Process of Li and B Revisited

Abstract

We reinvestigate effects of neutrino oscillations on the production of Li-7 and B-11 in core-collapse supernovae (SNe). During the propagation of neutrinos from the proto-neutron star, their flavors change, and the neutrino reaction rates for spallation of C-12 and He-4 are affected. In this work, corrected neutrino spallation cross sections for He-4 and C-12 are adopted. Initial abundances involving heavy s-nuclei and other physical conditions are derived in a new calculation of the SN 1987A progenitor in which the effects of the progenitor metallicity are included. A dependence of the SN nucleosynthesis and final yields of Li-7 and B-11 on the neutrino mass hierarchy are shown in several stellar locations. In the normal hierarchy case, the charged-current (CC) reaction rates of nu(e) are enhanced, and yields of proton-rich nuclei, along with Be-7 and C-11, are increased. In the inverted hierarchy case, the CC reaction rates of (nu) over bar (e) are enhanced, and yields of neutron-rich nuclei, along with Li-7 and B-11, are increased. We find that variation of the metallicity modifies the yields of Li-7, Be-7, B-11, and C-11. This effect is caused by changes in the neutron abundance during SN nucleosynthesis. Therefore, accurate calculations of Li and B production in SNe should take into account the metallicity of progenitor stars.