Dirac CP phases in a 3+1 neutrino scenario with $\mu-\tau$ symmetry

TL;DR

This paper investigates how a sterile neutrino in a 3+1 scheme influences Dirac CP phases, suggesting current data favor a normal hierarchy and light neutrino masses below 0.1 eV, with implications for neutrino symmetry breaking.

Contribution

It provides new predictions for Dirac CP phases in a 3+1 neutrino model considering sterile neutrino decay and symmetry breaking effects.

Findings

Current limits on δ_CP favor a normal hierarchy.

Lightest neutrino mass likely below 0.1 eV.

Other Dirac phases are predicted to be non-zero.

Abstract

A sterile neutrino in the $3+1$ scheme, where the sterile accounts for neutrino anomalies not explained solely by the weak active neutrinos, arises as a natural source for the breaking of the $\mu-\tau$ symmetry suggested by oscillation neutrino data. We explore the predictions for the Dirac CP phases in this scenario, with and without sterile neutrino decay, and show that current limits on $\delta_{CP}$ suggest a normal hierarchy and a lightest neutrino scale below 0.1~eV as the most plausible explanation for that, when Majorana phases are null. Other Dirac phases turn out to be non zero as well.