Michele Tammaro (INFN Firenze)

Transport equation for Ultra-High Energy neutrino events

We develop a first-principles formalism, based on the transport equation, to link the expected number of muons at neutrino telescopes to the flux of neutrinos at the Earth's surface. This framework allows a fast semi-analytical calculation of the expected number of events, accounting for systematic uncertainties, as well as clarifying the assumptions behind definitions commonly used in the literature. As a working case, we apply this formalism to analyze the high-energy muon event recorded by KM3NeT, with a reconstructed energy of approximately 120 PeV, in comparison with the non-observation of similar events by IceCube. We derive the tension between the two experiments under different assumptions for the neutrino flux, correcting previous results found in literature. Finally, the formalism can be easily extended to include other type of events, furthermore allowing one to treat potential beyond-the-Standard-Model sources of muons.