IceCube searches for GeV neutrino counterparts associated with high-energy starting events

TL;DR

This paper proposes a new IceCube analysis to search for GeV neutrinos associated with high-energy neutrino events, aiming to identify new astrophysical neutrino components and understand their sources.

Contribution

It introduces a novel statistical method and sensitivity analysis for detecting GeV neutrinos linked to high-energy events, with the first limits set on such emissions.

Findings

No statistically significant GeV neutrino signals were found.

First limits on GeV neutrino emission associated with VHE neutrino events.

Method improves background reduction for short time scale searches.

Abstract

The origin of the astrophysical neutrino flux observed by IceCube is largely unknown. To help decipher its astrophysical origin, we propose an IceCube analysis that conducts follow-up searches for GeV neutrinos associated with neutrino events above 60 TeV, which are known to have a high probability to be of astrophysical origin. It could not only identify a new component of the astrophysical neutrino flux, but also characterize how its spectrum extrapolates from GeV to PeV energies. This would in turn give valuable insights into the internal processes of neutrino sources. Astrophysical transients, such as collapsars, have been proposed as sources of time-correlated GeV- and high-energy neutrinos. Conducting this search in such short time scales allows for a substantial reduction in the dominant background rate for GeV neutrino candidate events. We introduce the statistical method and sensitivity of this search as well as dedicated data quality checks. None of the searches yield statistically significant results, and we present the first limits on GeV neutrino emission associated to VHE neutrino events at short time scales.