One-point fluctuation analysis of the high-energy neutrino sky

TL;DR

This paper introduces a novel one-point fluctuation analysis method for high-energy neutrino data, enabling better characterization of astrophysical sources like star-forming galaxies and blazars despite low statistics and lack of point source detection.

Contribution

It presents the first application of one-point fluctuation analysis to high-energy neutrino data, providing new insights into the astrophysical components of the neutrino flux.

Findings

Star-forming galaxies likely form a diffuse background.

Upper limits on blazar contributions to neutrino flux are established.

Skewness of blazar flux distribution affects upper limit estimates.

Abstract

We perform the first one-point fluctuation analysis of the high-energy neutrino sky. This method reveals itself to be especially suited to contemporary neutrino data, as it allows to study the properties of the astrophysical components of the high-energy flux detected by the IceCube telescope, even with low statistics and in the absence of point source detection. Besides the veto-passing atmospheric foregrounds, we adopt a simple model of the high-energy neutrino background by assuming two main extra-galactic components: star-forming galaxies and blazars. By leveraging multi-wavelength data from Herschel and Fermi, we predict the spectral and anisotropic probability distributions for their expected neutrino counts in IceCube. We find that star-forming galaxies are likely to remain a diffuse background due to the poor angular resolution of IceCube, and we determine an upper limit on the number of shower events that can reasonably be associated to blazars. We also find that upper limits on the contribution of blazars to the measured flux are unfavourably affected by the skewness of the blazar flux distribution. One-point event clustering and likelihood analyses of the IceCube HESE data suggest that this method has the potential to dramatically improve over more conventional model-based analyses, especially for the next generation of neutrino telescopes.