Diffuse neutrino flux measurements with the Baikal-GVD neutrino telescope

Abstract

We report on the first observation of the diffuse cosmic neutrino flux with the Baikal-GVD neutrino telescope. Using cascade-like events collected by Baikal-GVD in 2018--2021, a significant excess of events over the expected atmospheric background is observed. This excess is consistent with the high-energy diffuse cosmic neutrino flux observed by IceCube. The null cosmic flux assumption is rejected with a significance of 3.05$\ddot{I}ƒ$. Assuming a single power law model of the astrophysical neutrino flux with identical contribution from each neutrino flavor, the following best-fit parameter values are found: the spectral index ${\hat{I}}_{astro}^3$ = $2.58_{-0.33}^{+0.27}$ and the flux normalization $\ddot{I}{•}_{astro}$ = 3.04${}_{-1.21}^{+1.52}$ per one flavor at 100 TeV.

9 pages; 5 figures; 2 tables