Search for neutrinos in coincidence with gravitational wave events from the LIGO-Virgo O3a Observing Run with the Super-Kamiokande detector

TL;DR

This study searched for neutrinos coinciding with gravitational wave events from LIGO-Virgo's O3a run using Super-Kamiokande, finding no significant signals but setting limits on neutrino emissions from these sources.

Contribution

It is the first comprehensive search for neutrinos in coincidence with GW events across a wide energy spectrum using Super-Kamiokande, providing constraints on neutrino emissions.

Findings

No significant neutrino excess observed in coincidence with GW events.

Most significant event had a p-value of 7.8%, consistent with background.

Flux limits on neutrino emissions were established for various GW sources.

Abstract

The Super-Kamiokande detector can be used to search for neutrinos in time coincidence with gravitational waves detected by the LIGO-Virgo Collaboration (LVC). Both low-energy ($7-100$ MeV) and high-energy ($0.1-10^5$ GeV) samples were analyzed in order to cover a very wide neutrino spectrum. Follow-ups of 36 (out of 39) gravitational waves reported in the GWTC-2 catalog were examined; no significant excess above the background was observed, with 10 (24) observed neutrinos compared with 4.8 (25.0) expected events in the high-energy (low-energy) samples. A statistical approach was used to compute the significance of potential coincidences. For each observation, p-values were estimated using neutrino direction and LVC sky map ; the most significant event (GW190602_175927) is associated with a post-trial p-value of $7.8\%$ ($1.4\sigma$). Additionally, flux limits were computed independently for each sample and by combining the samples. The energy emitted as neutrinos by the identified gravitational wave sources was constrained, both for given flavors and for all-flavors assuming equipartition between the different flavors, independently for each trigger and by combining sources of the same nature.