Neutrino oscillations in three generations: A phenomenological overview

The recent observations of atmospheric nu events from the Super-Kamiokande experiment are compatible with two-flavor oscillations in the nu(mu) <----> nu(tau) channel ("standard" interpretation). Among the possible deviations from this standard picture, we investigate two cases: (1) Three-flavor osc illations and (2) a specific solution without oscillations (namely, neutrin o decay). While the first solution appears perfectly viable, provided that the 3 nu oscillations occur dominantly in the nu(mu) <----> nu(tau) channel and subdominantly in the nu(mu) <----> nu(e) channel, the second is shown to be incompatible with the data. The derivation of such results is based o n an updated analysis, including the latest 45 kTy data sample from Super-K amiokande, A comparison with our previous results, based on 33 kTy data, sh ows that the oscillation evidence is strengthened, and that the neutrino ma ss-mixing parameters are constrained in smaller ranges.