Leptonic commutators and clean T violation in neutrino oscillations

TL;DR

This paper demonstrates that terrestrial matter effects minimally contaminate genuine T violation signals in neutrino oscillations under certain experimental conditions, ensuring the reliability of T violation measurements.

Contribution

It introduces a method using lepton mass matrix commutators to evaluate matter effects on T violation in neutrino oscillations, showing these effects are negligible in many experiments.

Findings

Matter effects are negligible when 10^{-7} (L/km)^2 (GeV/E) << 1.

The same applies to CP-violating asymmetries in neutrino oscillations.

The approach helps distinguish genuine T violation from matter-induced effects.

Abstract

A realistic medium- or long-baseline neutrino experiment may suffer from terrestrial matter effects which are likely to contaminate the genuine T-violating asymmetry between \nu_\alpha \to \nu_\beta and \nu_\beta \to \nu_\alpha oscillations. With the help of the commutators of lepton mass matrices in matter, we show that this kind of contamination is negligible for a variety of experiments provided the neutrino beam energy E and the baseline length L satisfy the condition 10^{-7} (L/km)^2 (GeV/E) << 1. The same observation is true for the CP-violating term of the asymmetry between \nu_\alpha \to \nu_\beta and \bar{\nu}_\alpha \to \bar{\nu}_\beta oscillations in matter.