Constraints on the energy spectrum of the diffuse cosmic neutrino flux from the ANTARES neutrino telescope

TL;DR

This study analyzes 15 years of ANTARES neutrino data to search for cosmic neutrino flux, setting limits on its spectrum, especially below 20 TeV, and constraining models with softer spectral indices.

Contribution

It provides the first comprehensive limits on the diffuse cosmic neutrino flux using ANTARES data over 15 years, focusing on energies below 20 TeV.

Findings

No significant detection of cosmic diffuse neutrino flux.

Constraints on power-law spectra with spectral index softer than 2.8.

Limits on the flux below 20 TeV derived from ANTARES data.

Abstract

High-significance evidences of the existence of a high-energy diffuse flux of cosmic neutrinos have emerged in the last decade from several observations by the IceCube Collaboration. The ANTARES neutrino telescope took data for 15 years in the Mediterranean Sea, from 2007 to 2022, and collected a high-purity all-flavour neutrino sample. The search for a diffuse cosmic neutrino signal using this dataset is presented in this article. This final analysis did not provide a statistically significant observation of the cosmic diffuse flux. However, this is converted into limits on the properties of the cosmic neutrino spectrum. In particular, given the sensitivity of the ANTARES neutrino telescope between 1 and 50 TeV, constraints on single-power-law hypotheses are derived for the cosmic diffuse flux below 20 TeV, especially for power-law fits of the IceCube data with spectral index softer than 2.8.