Correlated, Precision Measurements of θ_{23} and $δ$ using only the Electron Neutrino Appearance Experiments

Abstract

Precision measurement of the leptonic CP violating phase $δ$ will suffer from the, then surviving, large uncertainty of sin^2 θ_{23} of 10-20% in the experimentally interesting region near maximal mixing of θ_{23}. We advocate a new method for determination of both θ_{23} and $δ$ at the same time using only the ν_e and \barν_e appearance channels, and show that sin^2 θ_{23} can be determined automatically with much higher accuracy, approximately a factor of six, than \sin δ. In this method, we identify a new degeneracy for the simultaneous determination of θ_{23} and δ, the θ_{23} intrinsic degeneracy, which must be resolved in order to achieve precision measurement of these two parameters. Spectral information around the vacuum oscillation maxima is shown to be the best way to resolve this degeneracy.