Michele Tammaro: Transport equation for Ultra-High Energy neutrino events

Thursday 6 Nov 2025, 11:00 → 12:00 Europe/Ljubljana

F1 tea room

We develop a first-principles formalism, based on the transport equation in the line-of-sight approximation, to link the expected number of muons at neutrino telescopes to the flux of neutrinos at the Earth's surface. We compute the distribution of muons inside Earth, arising from the up-scattering of neutrinos close to the detector, as well as from the decay of taus produced farther away. 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.