The role of neutrinos in explosive nucleosynthesis

We present a new primary nucleosynthesis process, the # p-process, occurring in supernovae (and possibly gamma-ray bursts) when strong neutrino fluxes create proton-rich ejecta. In this process, antineutrino absorptions in the proton-rich environment produce neutrons that are immediately captured by neutron-deficient nuclei. The capture of these neutrons permits to overcome the long beta-decay lifetimes of proton-rich nuclei like 64 Ge, allowing the nucleosynthesis flow to proceed to nuclei with mass numbers A < 64. This process is a possible candidate to explain the origin of the solar abundances of the light p-nuclei (such as 92,94 Mo and 96,98 Ru) and also offers a natural explanation for the large abundance of Sr (and other elements beyond Fe) seen in the very early stage of the galactic evolution.