Method for determination of |Ue3| in neutrino oscillation appearance experiments

We point out that determination of the MNS matrix element |Ue3|=s13 in long-baseline νμ→νe neutrino oscillation experiments suffers from large intrinsic uncertainty due to the unknown CP violating phase δ and sign of Δm213. We propose a new strategy for accurate determination of θ13; 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, θ13, and the sign of Δm213.