Challenging Lorentz noninvariant neutrino oscillations without neutrino masses

TL;DR

This paper demonstrates that current neutrino experiment data can exclude a broad class of Lorentz noninvariant models for massless neutrinos, reinforcing the standard mass-based oscillation paradigm.

Contribution

It provides the first comprehensive analysis ruling out the generalized bicycle model of Lorentz noninvariant neutrino oscillations using multiple experimental datasets.

Findings

Pure direction-dependent Lorentz violation is excluded by solar data.

Pure direction-independent Lorentz violation is ruled out by combined solar and long-baseline data.

Mixtures of Lorentz-violating terms are also excluded with KamLAND data.

Abstract

We show that the combined data from solar, long-baseline and reactor neutrino experiments can exclude the generalized bicycle model of Lorentz noninvariant direction-dependent and/or direction-independent oscillations of massless neutrinos. This model has five parameters, which is more than is needed in standard oscillation phenomenology with neutrino masses. Solar data alone are sufficient to exclude the pure direction-dependent case. The combination of solar and long-baseline data rules out the pure direction-independent case. With the addition of KamLAND data, a mixture of direction-dependent and direction-independent terms in the effective Hamiltonian is also excluded.