Unstable MeV neutrinos and primordial nucleosynthesis

por Sergio Pastor (SISSA - INFN, Trieste (Italy))

martes 9 mar. 1999 16:30 → 17:30 Europe/Madrid

Sala Seminarios (Dpto. de Fisica Teorica (UVEG))

The impact of unstable MeV tau neutrinos on primordial nucleosynthesis (BBN) is considered for masses and lifetimes in the intervals 0.1-20 MeV and 0.001-400 sec, respectively. The studied decay modes are nu_tau -> nu_mu(nu_e) + phi, where phi is a massless (or light) scalar. The Boltzmann kinetic equations are solved numerically without any simplifying assumptions. Depending on mass, lifetime, and decay channels of the tau neutrinos, the number of effective neutrino species at BBN (found from He-4), in addition to the 3 standard ones, varies from -2 to +2.5.