Enhanced Muonization by Active-Sterile Neutrino Mixing in Protoneutron Stars

Abstract

We study $\hat{I}{½}_{\hat{I}}¼$-$\hat{I}{½}_s$ and $\bar{\hat{I}}{½}_{\hat{I}}¼$-$\bar{\hat{I}}{½}_s$ mixing in the protoneutron star (PNS) created in a core-collapse supernova (CCSN). We point out the importance of the feedback on the general composition of the PNS in addition to the obvious feedback on the $\hat{I}{½}_{\hat{I}}¼$ lepton number. We show that for our adopted mixing parameters $\hat{I}´m^2\sim 10^2$~keV${}^2$ and ${\sin }^{2}2\hat{I}¸$ consistent with the current constraints, sterile neutrino production is dominated by the Mikheyev-Smirnov-Wolfenstein conversion of $\bar{\hat{I}}{½}_{\hat{I}}¼$ into $\bar{\hat{I}}{½}_s$ and that the subsequent escape of $\bar{\hat{I}}{½}_s$ increases the $\hat{I}{½}_{\hat{I}}¼$ lepton number, which in turn enhances muonization of the PNS primarily through $\hat{I}{½}_{\hat{I}}¼+n\to p+\hat{I}{¼}^{-}$. While these results are qualitatively robust, their quantitative effects on the dynamics and active neutrino emission of CCSNe should be evaluated by including $\hat{I}{½}_{\hat{I}}¼$-$\hat{I}{½}_s$ and $\bar{\hat{I}}{½}_{\hat{I}}¼$-$\bar{\hat{I}}{½}_s$ mixing in the simulations.

v2: 11 pages, 7 figures. Minor clarifications added, conclusion unchanged. Matches version published in PRD