The Mu and Tau Number of Supernovae

Abstract

The neutrino-nucleon cross section is slightly larger than that for $\bar{\nu }-N$. Therefore, $\bar{\nu }$ will escape more quickly from core collapse supernovae leaving the star $\nu$ rich. A diffusion formalism is used to calculate the time evolution of the mu and tau lepton number densities. These quickly reach steady state equilibria. We estimate that a protoneutron star with a maximum temperature near 50 MeV will contain over 50 % more ${\nu }_{\mu }$ and ${\nu }_{\tau }$ than ${\bar{\nu }}_{\mu }$ and ${\bar{\nu }}_{\tau }$. Supernovae may be the only known systems with large mu and or tau lepton numbers.

5 pages, one ps figure, submitted to Phys. Let. B