Can lepton flavor violating interactions explain the atmospheric neutrino problem?

TL;DR

This paper assesses whether flavor-changing neutrino interactions could explain the atmospheric neutrino problem and concludes that such interactions are too constrained by existing bounds to be a viable solution.

Contribution

The study provides a model-independent analysis showing that flavor-changing neutrino interactions cannot account for the atmospheric neutrino anomaly due to existing experimental bounds.

Findings

Flavor-changing neutrino interactions are too small to solve the atmospheric neutrino problem.

Upper bounds from tau decay experiments severely limit non-standard neutrino interactions.

Z-induced flavor changing neutral currents are negligible for this issue.

Abstract

We investigate whether flavor changing neutrino interactions (FCNIs) can be sufficiently large to provide a viable solution to the atmospheric neutrino problem. Effective operators induced by heavy boson exchange that allow for flavor changing neutrino scattering off quarks or electrons are related by an $SU(2)_L$ rotation to operators that induce anomalous tau decays. Since $SU(2)_L$ violation is small for New Physics at or above the weak scale, one can use the upper bounds on lepton flavor violating tau decays or on lepton universality violation to put severe, model-independent bounds on the relevant non-standard neutrino interactions. Also $Z$-induced flavor changing neutral currents, due to heavy singlet neutrinos, are too small to be relevant for the atmospheric neutrino anomaly. We conclude that the FCNI solution to the atmospheric neutrino problem is ruled out.