Spectral split in prompt supernova neutrino burst: Analytic three-flavor treatment

TL;DR

This paper provides an analytical three-flavor framework to understand the spectral split phenomenon in supernova neutrino bursts, revealing that two closely spaced splits arise from conserved flavor-lepton numbers in specific density profiles.

Contribution

It introduces an analytic three-flavor treatment of spectral splits in supernova neutrinos, explaining the phenomenon as a MSW prepared spectral split with two narrowly spaced features.

Findings

Spectral splits are explained analytically as MSW prepared features.

Two narrowly spaced splits are identified in the three-flavor treatment.

Splits are determined by conserved flavor-lepton number combinations.

Abstract

The prompt nu_e burst from a core-collapse supernova (SN) is subject to both matter-induced flavor conversions and strong neutrino-neutrino refractive effects. For the lowest-mass progenitors, leading to O-Ne-Mg core SNe, the matter density profile can be so shallow that the usual MSW matter effects occur within the dense-neutrino region close to the neutrino sphere. In this case a ``split'' occurs in the emerging spectrum, i.e., the nu_e flavor survival probability shows a step-like feature. We explain this feature analytically as a ``MSW prepared spectral split.'' In a three-flavor treatment, the step-like feature actually consists of two narrowly spaced splits. They are determined by two combinations of flavor-lepton numbers that are conserved under collective oscillations.