Time-Integrated Southern-Sky Neutrino Source Searches with 10 Years of IceCube Starting-Track Events at Energies Down to 1 TeV

TL;DR

This paper presents a decade-long analysis of IceCube starting-track events at energies down to 1 TeV, improving sensitivity to southern-sky neutrino sources, especially Galactic sources, by using the new ESTES selection to reduce backgrounds.

Contribution

The study applies the new IceCube ESTES method to search for astrophysical neutrinos over 10 years, enhancing detection sensitivity for southern-sky sources at energies as low as 1 TeV.

Findings

No significant neutrino excess detected from sources.

Set limits on Galactic plane neutrino emission.

Improved sensitivity to southern-sky neutrino sources.

Abstract

In the IceCube Neutrino Observatory, a signal of astrophysical neutrinos is obscured by backgrounds from atmospheric neutrinos and muons produced in cosmic-ray interactions. IceCube event selections used to isolate the astrophysical neutrino signal often focus on t/he morphology of the light patterns recorded by the detector. The analyses presented here use the new IceCube Enhanced Starting Track Event Selection (ESTES), which identifies events likely generated by muon neutrino interactions within the detector geometry, focusing on neutrino energies of 1-500 TeV with a median angular resolution of 1.4{\deg}. Selecting for starting track events filters out not only the atmospheric-muon background, but also the atmospheric-neutrino background in the southern sky. This improves IceCube's muon neutrino sensitivity to southern-sky neutrino sources, especially for Galactic sources that are not expected to produce a substantial flux of neutrinos above 100 TeV. In this work, the ESTES sample was applied for the first time to searches for astrophysical sources of neutrinos, including a search for diffuse neutrino emission from the Galactic plane. No significant excesses were identified from any of the analyses; however, constraining limits are set on the hadronic emission from TeV gamma-ray Galactic plane objects and models of the diffuse Galactic plane neutrino flux.