Non-standard neutrino self-interactions in a supernova and fast flavor conversions

TL;DR

This paper investigates how non-standard neutrino self-interactions influence flavor conversions in supernovae, revealing new conditions for fast oscillations and their interplay with collective effects through analytical and numerical methods.

Contribution

It introduces the effects of NSSI on neutrino flavor stability, analytically demonstrates suppression and emergence of fast oscillations, and numerically explores their interplay in supernova models.

Findings

NSSI can cause both suppression and enhancement of flavor oscillations.

Flavor-violating NSSI enable fast oscillations even with obtuse beam angles.

Numerical solutions show complex interplay of fast and slow conversions with NSSI.

Abstract

We study the effects of non-standard self-interactions (NSSI) of neutrinos streaming out of a core-collapse supernova. We show that with NSSI, the standard linear stability analysis gives rise to linearly as well as exponentially growing solutions. For a two-box spectrum, we demonstrate analytically that flavor-preserving NSSI lead to a suppression of bipolar collective oscillations. In the intersecting four-beam model, we show that flavor-violating NSSI can lead to fast oscillations even when the angle between the neutrino and antineutrino beams is obtuse, which is forbidden in the Standard Model. This leads to the new possibility of fast oscillations in a two-beam system with opposing neutrino-antineutrino fluxes, even in the absence of any spatial inhomogeneities. Finally, we solve the full non-linear equations of motion in the four-beam model numerically, and explore the interplay of fast and slow flavor conversions in the long-time behavior, in the presence of NSSI.