Neutrino-induced reactions in core-collapse supernovae : Effects on the electron fraction

Neutrino-induced reactions are a basic ingredient in astrophysical processes like star evolution. The existence of neutrino oscillations affects the rate of nuclear electroweak decays which participates in the chain of events that determines the fate of the star. Among the processes of interest, the production of heavy elements in core-collapse supernovae is strongly dependent upon neutrino properties, like the mixing between different species of neutrinos. In this work, we study the effects of neutrino oscillations upon the electron fraction as a function of the neutrino mixing parameters, for two schemes: the 1+1-scheme (one active neutrino and one sterile neutrino) and the 2+1-scheme (two active neutrinos and one sterile neutrino). We have performed this analysis considering a core-collapse supernovae and determined the physical conditions needed to activate the nuclear reaction chains involved in the r-process. We found that the interactions of the neutrinos with matter and among themselves and the initial amount of sterile neutrinos in the neutrino-sphere might change the electron fraction, therefore affecting the onset of the r-process. We have set constrains on the active-sterile neutrino mixing parameters. They are the square-mass-difference Δm142 , the mixing angle sin2214, and the hindrance factor ξs for the occupation of sterile neutrinos. The calculations have been performed for different values of Xα, which is the fraction of alpha particles. For Xα=0 the r-process is taking place if Δm142≥2eV2, sin22140.8 and ξs0.5. For larger values of Xα the region of parameters is strongly reduced. The present results are compared to results available in the literature.Facultad de Ciencias Astronómicas y GeofísicasFacultad de Ciencias ExactasInstituto de Física La Plat