SN1987A neutrino burst: limits on flavor conversion

TL;DR

This study reanalyzes SN1987A neutrino data to constrain flavor conversion without assuming a specific mechanism, finding evidence for an accretion phase and a preference for normal mass ordering under certain conditions.

Contribution

It introduces a model-independent analysis of neutrino flavor conversion using survival probability as a free parameter, expanding beyond previous mechanism-specific studies.

Findings

No strong limits on survival probability above 1σ for time-integrated models.

Strong rejection of zero survival probability in models with an accretion phase.

Preference for normal mass ordering when only MSW effect is considered.

Abstract

In this paper, we revisit the SN1987A neutrino data to see its constraints on flavor conversion. We are motivated by the fact that most works that analyze this data consider a specific conversion mechanism, such as the MSW (Mikheyev-Smirnov-Wolfenstein) effect, although flavor conversion is still an open question in supernovae due to the presence of neutrino-neutrino interactions. In our analysis, instead of considering a specific conversion mechanism, we let the electron antineutrino survival probability $P_{\overline{e}\overline{e}}$ be a free parameter. We fit the data from Kamiokande-II, Baksan, and IMB detected spectrum with two classes of models: time-integrated and time-dependent. For the time-integrated model, it is not possible to put limits above $1\sigma$ (68% confidence level) on the survival probability. The same happens for the time-dependent model when cooling is the only mechanism of antineutrino emission. However, for models considering an accretion phase, $P_{\overline{e}\overline{e}}\sim0$ is strongly rejected, showing a preference for the existence of an accretion component in the detected antineutrino flux, and a preference for normal mass ordering when only the MSW is present.