Towards Powerful Probes of Neutrino Self-Interactions in Supernovae

Abstract

Neutrinos remain mysterious. As an example, enhanced self-interactions ($\hat{I}½$SI), which would have broad implications, are allowed. At the high neutrino densities within core-collapse supernovae, $\hat{I}½$SI should be important, but robust observables have been lacking. We show that $\hat{I}½$SI make neutrinos form a tightly coupled fluid that expands under relativistic hydrodynamics. The outflow becomes either a burst or a steady-state wind; which occurs here is uncertain. Though the diffusive environment where neutrinos are produced may make a wind more likely, further work is needed to determine when each case is realized. In the burst-outflow case, $\hat{I}½$SI increase the duration of the neutrino signal, and even a simple analysis of SN 1987A data has powerful sensitivity. For the wind-outflow case, we outline several promising ideas that may lead to new observables. Combined, these results are important steps towards solving the 35-year-old puzzle of how $\hat{I}½$SI affect supernovae.

5+19 pages, 4+14 figures. Accepted for publication in Phys.Rev.Lett. Match the version to be published: minor revisions for clarity; moved discussion about supernova neutrino properties to Supplemental Material C; updated references