Perturbations to \mu-\tau\ symmetry in neutrino mixing

Understand

Many neutrino mixing scenarios that have \mu-\tau symmetry with \theta_{13}=0 are in disagreement with recent experimental results that indicate a nonzero value for \theta_{13}.

• We investigate the effect of small perturbations on Majorana mass matrices with \mu-\tau symmetry and derive analytic formulae for the corrections to the mixing angles.
• We find that since m_1 and m_2 are nearly degenerate, \mu-\tau symmetry mixing scenarios are able to explain the experimental data with about the same size perturbation for most values of \theta_{12}.
• This suggests that the underlying unperturbed mixing need not have \theta_{12} close to the experimentally preferred value.