Non-standard neutrino interactions in the Earth and the flavor of astrophysical neutrinos

TL;DR

This paper investigates how non-standard neutrino interactions within the Earth can alter the flavor composition of ultra high-energy astrophysical neutrinos, revealing potential deviations from standard oscillation predictions depending on source flavor composition.

Contribution

It introduces the impact of Earth matter effects on neutrino flavor content, highlighting the dependence on arrival direction and source flavor, which was not fully explored before.

Findings

Large deviations from standard oscillations are possible within current non-standard interaction limits.

Flavor content depends on the neutrino's arrival direction due to Earth matter effects.

No significant corrections are expected for sources with pion-muon decay-chain dominance.

Abstract

We study the modification of the detected flavor content of ultra high-energy astrophysical neutrinos in the presence of non-standard interactions of neutrinos with the Earth matter. Unlike the case of new physics affecting the propagation from the source to the Earth, non-standard Earth matter effects induce a dependence of the flavor content on the arrival direction of the neutrino. We find that, within the current limits on non-standard neutrino interaction parameters, large deviations from the standard 3-nu oscillation predictions can be expected, in particular for fluxes dominated by one flavor at the source. Conversely they do not give sizable corrections to the expectation of equalized flavors in the Earth for sources dominated by production via pion-muon decay-chain.