NEUTRINO OSCILLATIONS WITH 3-GENERATION MIXINGS AND MASS HIERARCHY

We have analyzed the results of reactor and accelerator neutrino oscil lation experiments in a model with mixing of three neutrino fields and a neutrino mass hierarchy. It is shown that v(mu) reversible arrow v( e) oscillations with 0.6 less than or equal to Delta m(2) less than or equal to 100 eV(2) and amplitude larger than 2 x 10(-3) are not compa tible with the existing limits on neutrino oscillations if the non-dia gonal elements of the mixing matrix are small. Thus, if the excess of positron events recently observed in the LSND experiment is due to (v) over bar(mu) --> (v) over bar(e) oscillations, the mixing in the lept on sector is basically different from the CKM mixing of quarks.