Sterile neutrinos and supernova nucleosynthesis

A light sterile neutrino species has been introduced to explain simultaneously the solar and atmospheric neutrino puzzles and the results of the LSND experiment, while providing for a hot component of dark matter. Employing this scheme of neutrino masses and mixings, we show how matter-enhanced active-sterile $({\nu }_{\mu ,\tau }\rightleftharpoons {\nu }_s)$ neutrino transformation followed by active-active $({\nu }_{\mu ,\tau }\rightleftharpoons {\nu }_e)$ neutrino transformation can solve robustly the neutron deficit problem encountered by models of $r-\mathrm{process}$ nucleosynthesis associated with neutrino-heated supernova ejecta.