Indirect Search for CP Violation in Neutrino Oscillations

We propose the indirect search for the CP violating phase in the long baseline $\n_\m \Ar\n_e$ oscillation experiment, in which two scenarios of the neutrino mass hierarchy are discussed in the three family model. The CP violatig phase effect is clearly found in the scenario: the LSND data plus the atmospheric neutrino deficit. The phase dependence of the oscillation probability is explicitly shown by using typical parameters of the K2K experiment. The matter effect is negligibly small. In order to select the scenario of the neutrino mass hierarchy, the measurement of the $\n_e\Ar\n_\tau$ oscillation is also proposed in the long baseline experiment.