Evidence for a Spectral Break or Curvature in the Spectrum of Astrophysical Neutrinos from 5 TeV--10 PeV

TL;DR

This study presents improved measurements of astrophysical neutrino spectra, revealing a spectral break or curvature between 5 TeV and 10 PeV, challenging simple power-law models.

Contribution

The paper provides the first strong evidence for a spectral break or curvature in the astrophysical neutrino spectrum using IceCube data.

Findings

Evidence of a harder spectrum below 30 TeV compared to higher energies.

A log parabola or broken power law better describes the spectrum than a single power law.

Single power law rejected over 5 TeV-10 PeV with >4σ significance.

Abstract

We report improved measurements of the all flavor astrophysical neutrino spectrum with IceCube by combining complementary neutrino samples in two independent analyses. Both analyses show evidence of a harder spectrum at energies below $\sim$30~TeV compared to higher energies where the spectrum is well characterized by a power law. The spectrum is better described by a log parabola or a broken power law, the latter being the preferred model. Both, however, reject a single power law over an energy range 5~TeV-10~PeV with a significance $>4\sigma$, providing new constraints on properties of cosmic neutrino sources.