Effects of Matter in Neutrino Oscillations and Determination of Neutrino Mass Hierarchy at Long-baseline Experiments

TL;DR

This paper discusses how matter effects influence neutrino oscillations in long-baseline experiments and how these effects can help determine the neutrino mass hierarchy, with recent experiments providing significant insights.

Contribution

It analyzes the impact of matter effects on neutrino oscillations and demonstrates how combined experimental data can reject incorrect mass hierarchy hypotheses.

Findings

Matter effects modify neutrino oscillation probabilities in media.

Combined NOvA and T2K data can reject wrong hierarchy for over 20% of CP phases.

Experiments can distinguish neutrino mass hierarchy with significant confidence.

Abstract

Neutrino oscillations change when in media in comparison to vacuum oscillations due to the scattering of neutrinos on matter constituents, electrons particularly. This can be easily described by introducing new effective matter mixing angles and squared mass-splittings. Exploiting the matter effects and subsequent enhancement or suppression of oscillation probabilities can be used to determine the hierarchy of neutrino mass states. Recent long-baseline experiments NO$\nu$A and T2K investigate this possibility. Together NO$\nu$A and T2K combined can reject the wrong hierarchy for more than 20% of all possible values of yet unknown CP violating phase $\delta$ $\in$ [-180$^\circ$, 180$^\circ$].