On T violation in non-standard neutrino oscillation scenarios

TL;DR

This paper explores how new physics scenarios can induce T violation in neutrino oscillations, analyzing fundamental versus environmental effects and implications for long-baseline experiments like DUNE and T2HK.

Contribution

It introduces a general, model-independent parameterization for flavor evolution that captures various new physics effects and studies T violation in different experimental contexts.

Findings

T violation in disappearance channels requires new physics affecting production and detection.

Matter density variations influence T violation signals, studied via perturbation theory.

Results inform model-independent tests of T violation in upcoming neutrino experiments.

Abstract

We discuss time reversal (T) violation in neutrino oscillations in generic new physics scenarios. A general parameterization is adopted to describe flavour evolution, which captures a wide range of new physics effects, including non-standard neutrino interactions, non-unitarity, and sterile neutrinos in a model-independent way. In this framework, we discuss general properties of time reversal in the context of long-baseline neutrino experiments. Special attention is given to fundamental versus environmental T violation in the presence of generic new physics. We point out that T violation in the disappearance channel requires new physics which modifies flavour mixing at neutrino production and detection. We use time-dependent perturbation theory to study the effect of non-constant matter density along the neutrino path, and quantify the effects for the well studied baselines of the DUNE, T2HK, and T2HKK projects. The material presented here provides the phenomenological background for the model-independent test of T violation proposed by us in Ref. [1].