Measuring the Neutrino Flux in Segments along the Galactic Plane with IceCube

TL;DR

This paper presents a segmented analysis of the galactic neutrino flux using IceCube data, aiming to improve understanding of neutrino emission variations along the Milky Way's plane and distinguish hadronic processes.

Contribution

It introduces a novel segmentation approach along the galactic plane with an unbinned likelihood method to analyze spectral and flux variations in neutrino emission.

Findings

First segmentation-based analysis of galactic neutrino flux

Potential to differentiate hadronic from leptonic emission

Provides regional insights into neutrino flux and spectral index

Abstract

Gamma-ray emission from the plane of the Milky Way is understood as partly originating from the interaction of cosmic rays with the interstellar medium. The same interaction is expected to produce a corresponding flux of neutrinos. In 2023, IceCube reported the first observation of this galactic neutrino flux at 4.5$\sigma$ confidence level. The analysis relied on neutrino flux predictions - based on gamma ray observations - to model the expected neutrino emission from the galactic plane. Three signal hypotheses describing different possible spatial and energy distributions were tested, where the single free parameter in each test was the normalization of the neutrino flux. We present first results of an analysis that can improve the characterization of Galactic neutrino emission by dividing the galactic plane into segments in galactic longitude. An unbinned maximum-likelihood analysis is used that can fit the spectral index and the flux normalization separately in each segment. While gamma ray telescopes can not differentiate between hadronic and leptonic emission, neutrino production must come from hadronic processes. Measuring a spectral index can further help to understand the contribution of unresolved neutrino sources inside the galactic plane. This work uses a full-sky cascade dataset and provides model-independent insight into the variation of the neutrino flux and energy distribution from different regions of the galactic plane.