The temporal distribution of SN1987A neutrino events

TL;DR

This paper refines the timing of SN1987A neutrino events, reducing uncertainties and analyzing their origin, supporting the standard inverse beta decay interpretation with improved temporal precision.

Contribution

It introduces a high-precision alignment method for neutrino data, significantly reducing timing uncertainties and providing a rigorous timeline for supernova neutrino analysis.

Findings

Baksan timestamps require a 30.4 s correction

Kamiokande-II timestamps require a 6.4 s delay

Results favor accretion phase electron anti-neutrino origin over neutronization burst

Abstract

The interpretation of the SN1987A neutrino data continues to be hindered by significant absolute timing uncertainties and a well-known tension in the angular distributions. We perform a quantitative, high-precision alignment of the Kamiokande-II and Baksan data with the IMB clock, using for the first time the relative time offset (RTO) and reducing the temporal uncertainty by two orders of magnitude to the sub-second level. The chi-square analysis shows that Baksan's absolute timestamps require an advancement of 30.4 s, while those of Kamiokande-II require a delay of about 6.4 s. The knowledge of the unified timeline provides a necessary and rigorous basis for testing whether the first Kamiokande-II event arose from the neutronization burst - a possibility motivated by its angular properties. Our analysis favors an accretion phase electron anti-neutrino origin over a neutronization-burst origin, with a likelihood ratio of 3-6, depending on the specific MSW oscillation scenario. This result corroborates the standard interpretation - that only inverse beta decay events were detected. Our framework yields the most stringent constraints to date on the SN1987A chronology and establishes a precision benchmark for future Galactic supernova observations.