NEUTRINO OSCILLATIONS IN THE FRAMEWORK OF 3-GENERATION MIXINGS WITH MASS HIERARCHY

We have analyzed the results of reactor and accelerator neutrino oscil lation experiments in the framework of a general model with mixing of three neutrino fields and a neutrino mass hierarchy that can accommoda te the results of the solar neutrino experiments. It is shown that nu( mu)reversible arrow nu(e) oscillations with 0.6 less than or equal to Delta m(2) less than or equal to 100 e(V)2 and amplitude larger than 2 x 10(-3) are not compatible with the existing limits on neutrino osci llations if the non-diagonal elements of the mixing matrix \U-e3\ and \U-mu 3\ are small. Thus, if the excess of electron events recently ob served in the LSND experiment is due to nu(mu)reversible arrow nu(e) o scillations, the mixing in the lepton sector is basically different fr om the CKM mixing of quarks. If this type of mixing is realized in nat ure, the observation of nu(mu)reversible arrow nu(e) oscillations woul d not influence nu(mu)reversible arrow nu(tau) oscillations that are b eing searched for in the CHORUS and NOMAD experiments.