Effects of the Metallicity on Li and B Production in Supernova Neutrino Process

Abstract

The neutrino process (ν-process) for the production of 7 Li and 11 B in core-collapse supernovae (SNe) is extensively investigated. Initial abundances of s-nuclei and other physical conditions are derived from an updated calculation of the SN 1987A progenitor. The nuclear reaction network including neutrino reactions is constructed with the variable order Bader-Deuflhard integration method. We find that yields of 7 Li and 11 B significantly depend on the stellar metallicity while they are independent of the weak s-process during the stellar evolution. When the metallicity is high, there are more neutron absorbers, i.e., 56 Fe, 14 N (from initial CNO nuclei), and 54 Fe, and the neutron abundance is small during the ν-process. Since 7 Be is predominantly destroyed via 7 Be(n,p) 7 Li, a change in the neutron abundance results in different 7 Be yields. Then, the calculated yield ratio 7 Li/ 11 B=0.93 for the solar metallicity is larger than that for the SN 1987A 7 Li/ 11 B=0.80 by 16 % in the inverted mass hierarchy case. We analyze contributions of respective reactions as well as abundance evolution, and clarify the ν-process of 7 Li and 11 B.