Experimental Highlights from Super-Kamiokande

Recent results from Super-Kamiokande are presented. Solar and atmospheric neutrinos have been studied in detail since 1996. The data of atmospheric neutrinos show strong up-down asymmetry and provide evidence for oscillation along their way through Earth. The selected data support oscillations of νμ → ντ and rule out the two-flavor νμ → νs oscillation. The underlying parameters for the νμ → ντ oscillations are determined to be [Formula: see text] and sin 22θ > 0.89ata90%C.L. Proton decays into various final states have been searched for but no evidence was found. Lower limits on the partial lifetimes are presented for major decay modes, especially those for p → e+π0 and [Formula: see text] are 5.0 × 1033 yr and 1.9 × 1033 yr , respectively.

Neutrino Masses and Mixing

Recent results on neutrino masses and mixing are presented. There is convincing evidence for nonzero but tiny masses of at least two flavor neutrinos, based on two types of neutrino oscillations, solar and atmospheric neutrinos. The large mixing angle between first and second flavors and also the one between the second and third flavors were found, quite contrary to small mixing angles among quark flavors, and pose a new mystery.

NEUTRINO MASS: PEEPING BEYOND THE STANDARD MODEL

Evidence in support of a nonzero neutrino mass, through the phenomenon of oscillations, is steadily becoming more compelling. A pedagogic introduction to vacuum neutrino oscillations and resonant flavour conversion is presented in this paper, prefaced by a thumbnail sketch of the relevant properties of the neutrino as embodied in the Standard Model of particle physics. The recent results from solar and atmospheric neutrinos are summarised and their combined implications on neutrino properties are outlined. Some attempts to incorporate a nonzero neutrino mass in extensions of the Standard Model are briefly discussed.