The first second of SN1987A neutrino emission

TL;DR

This paper analyzes the initial neutrino emission from SN1987A, revealing a significant early accretion phase with implications for neutrino oscillations and mass hierarchy interpretations.

Contribution

It provides the first detailed analysis of the first second of SN1987A neutrino data, highlighting a potential initial accretion phase and its impact on neutrino oscillation models.

Findings

Evidence for a 3.2 sigma initial accretion phase.

Approximately 20% or more of neutrino energy emitted during initial phase.

Normal mass hierarchy oscillations are consistent; inverted hierarchy interpretations are problematic.

Abstract

A large fraction of SN1987A electron antineutrino events has been recorded in the first second. We study how this observation fits into the conventional paradigm for neutrino emission, and show that there is a 3.2 sigma hint for an initial accretion phase. This phase involves a large fraction of the energy emitted in neutrinos and antineutrinos, about 20 % or larger. The occurrence of neutrino oscillations strengthens these inferences. We discuss why three flavor oscillations with normal mass hierarchy are completely acceptable, whereas oscillations with inverted mass hierarchy require more troublesome interpretations, if theta(13) is above 0.5-1 degrees.