Extended search for point sources of neutrinos below and above the horizon: Covering energies from TeV to EeV with IceCube

TL;DR

This paper introduces a novel method for neutrino point source searches with IceCube, including both up-going and down-going events, extending the observable sky and energy range up to EeV energies by suppressing background through energy-sensitive selection.

Contribution

It presents the first combined approach to include down-going and up-going muon events in neutrino point source searches, expanding sky coverage and energy sensitivity.

Findings

No significant excess above background observed.

Extended sky coverage to large parts of the Southern hemisphere.

Enhanced energy reach up to EeV energies.

Abstract

Point source searches with neutrino telescopes like IceCube are normally restricted to one hemisphere, due to the selection of up-going events as a way of rejecting the atmospheric muon background. In this work we show that the down-going region above the horizon can be included in the search by suppressing the background through energy-sensitive selection procedures. This approach increases the reach to the EeV regime of the signal spectrum, which was previously not accessible due to the absorption of neutrinos with energies above a PeV inside the Earth. We present preliminary results of this analysis, which for the first time includes up-going as well as down-going muon events in a combined approach. We used data collected with IceCube in a configuration of 22 strings. No significant excess above the atmospheric background is observed. While other analyses provided results for the Northern hemisphere, this new approach extends the field of view to a large part of the Southern sky, which was previously not covered with IceCube.