Galactic and Extragalactic Analysis of the Astrophysical Muon Neutrino Flux with 12.3 years of IceCube Track Data

TL;DR

This study uses 12.3 years of IceCube muon neutrino data to search for galactic diffuse emission and measure the isotropic astrophysical neutrino flux, utilizing directional information and spectral analysis.

Contribution

It presents a dedicated search for galactic neutrino emission using a large dataset and tests a recent cosmic ray-based model prediction with a likelihood fit.

Findings

Detected a galactic emission component with 2.7σ significance.

Measured the scaling factor of the galactic emission model as 2.9 ± 1.1.

Provided spectral measurements of the isotropic astrophysical neutrino flux.

Abstract

The Ice Cube Neutrino Observatory has been measuring an isotropic astrophysical neutrino flux in multiple detection channels for almost a decade. Galactic diffuse emission, which arises from the interactions between cosmic rays and the interstellar medium, is an expected signal in IceCube. The superposition of an extragalactic flux and a galactic flux results in directional structure and variations in the spectrum. In this work, we use 12.3 years of high-purity muon-neutrino induced muon track data to perform a dedicated search for this galactic emission, combined with a spectral measurement of the isotropic astrophysical neutrino flux. To distinguish a galactic component from the dominant atmospheric and isotropic astrophysical components, the precise directional information available for muon tracks is fully utilized in a three-dimensional forward folding likelihood fit. We test a state-of-the-art model prediction of galactic diffuse emission based on recent cosmic ray data (CRINGE). We fit this prediction as a template scaled by a factor $\Psi_{\mathrm{CRINGE}}$, and find $2.9\pm 1.1 \times \Psi_{\mathrm{CRINGE}}$ with a significance of $2.7\sigma$ in an energy range between 400 GeV and 60 TeV in the Northern Sky.