Method for Determination of $|U_{e3}|$ in Neutrino Oscillation Appearance Experiments

Abstract

We point out that determination of the MNS matrix element |U_{e3}| = s_{13} in long-baseline ν_μ \to ν_e neutrino oscillation experiments suffers from large intrinsic uncertainty due to the unknown CP violating phase δand sign of Δm^2_{13}. We propose a new strategy for accurate determination of $θ_{13}$; tune the beam energy at the oscillation maximum and do the measurement both in neutrino and antineutrino channels. We show that it automatically resolves the problem of parameter ambiguities which involves δ, θ_{13}, and the sign of Δm^2_{13}.