# Search for astrophysical sources of neutrinos using cascade events in IceCube

## TL;DR

This paper reports the first search for astrophysical neutrino sources using cascade events in IceCube, demonstrating improved sensitivity over traditional track-based methods, but finding no significant source clustering in the analyzed data.

## Contribution

It introduces a novel cascade-based search method for astrophysical neutrino sources in IceCube, enhancing sensitivity especially in the southern sky.

## Key findings

- No significant clustering of cascade events was observed.
- Cascade analysis provides improved sensitivity for certain sky regions.
- The method is effective for detecting extended or soft-spectrum sources.

## Abstract

The IceCube neutrino observatory has established the existence of a flux of high-energy astrophysical neutrinos inconsistent with the expectation from atmospheric backgrounds at a significance greater than $5\sigma$. This flux has been observed in analyses of both track events from muon neutrino interactions and cascade events from interactions of all neutrino flavors. Searches for astrophysical neutrino sources have focused on track events due to the significantly better angular resolution of track reconstructions. To date, no such sources have been confirmed. Here we present the first search for astrophysical neutrino sources using cascades interacting in IceCube with deposited energies as small as 1 TeV. No significant clustering was observed in a selection of 263 cascades collected from May 2010 to May 2012. We show that compared to the classic approach using tracks, this statistically-independent search offers improved sensitivity to sources in the southern sky, especially if the emission is spatially extended or follows a soft energy spectrum. This enhancement is due to the low background from atmospheric neutrinos forming cascade events and the additional veto of atmospheric neutrinos at declinations $\lesssim-30^\circ$.