Dirac CP phases in a 3+1 neutrino scenario with μ - τ symmetry

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.

Automated summary

A sterile neutrino in the 3+1 scheme is a natural source to explain neutrino anomalies not solely explained by weak active neutrinos. This study explores the predictions for the Dirac CP phases in this scenario, finding that current limits on δ(CP) suggest a normal hierarchy and a lightest neutrino scale below 0.1 eV as the most plausible explanation. Additionally, other Dirac phases are shown to be non-zero as well.