Cross-correlation study between the Fermi-LAT UGRB and the IceCube neutrino events

With the coincident detections of electromagnetic radiation together with gravitational waves (GW 170817) or neutrinos (TXS 0506+056), the new era of multimessenger astrophysics has begun. Particularly interesting are the searches for correlation between the high-energy astrophysical neutrinos detected by the IceCube (IC) Observatory and gamma-ray photons detected by the Fermi Large Area Telescope (LAT). So far, only sources resolved by the LAT have been considered in correlation with IC neutrinos, neglecting any emission from sources too faint to be resolved individually. Here, we present the first cross-correlation analysis considering unresolved gamma-ray background (UGRB) and IC events. We perform a careful sensitivity study and place upper limits on the fraction of the observed neutrinos that would be produced in proton-proton or proton-gamma interactions from the population of sources contributing to the UGRB emission and dominating its spatial anisotropy: blazars.