New index of CP phase effect and θ13 screening in long baseline neutrino experiments

We introduce a new index of the leptonic CP phase dependence ICP and derive the maximal condition for this index in a simple and general form. ICP≃100% may be realized even in the JPARC experiment. In the case that the 1-3 mixing angle can be observed in the next generation reactor experiments, namely sin22θ13>0.01, and nevertheless νe appearance signal cannot be observed in the JPARC experiment, we conclude that the CP phase δ becomes a value around 135° (45°) for Δm312>0(Δm312<0) without depending the uncertainties of solar and atmospheric parameters.