Corfu Summer Institute on Elementary Particle Physics, 1998 PROCEEDINGS Aspects of Neutrino Masses and Lepton-Number Violation in the light of the Super-Kamiokande data

Abstract: We discuss aspects of neutrino masses and lepton-number violation, in the light of the observations of Super-Kamiokande. As a rst step, we use the data from various experiments, in order to obtain a phenomenological understanding of neutrino mass textures. We then investigate how the required patterns of neutrino masses and mixings are related to the flavour structure of the underlying theory. In supersymmetric extensions of the Standard Model, renormalisation group eects can have important implications: for small tan, b{ unication indicates the presence of signicant { flavour mixing. The evolution of the neutrino mixing may be described by simple semi-analytic expressions, which conrm that, for large tan, very small mixing at the GUT scale may be amplied to maximal mixing at low energies, and vice versa. Passing to specic models, we rst discuss the predictions for neutrino masses in dierent GUT models (including superstring-embedded solutions). Imposing the requirement for successful leptogenesis may give additional constraints on the generic structure of the neutrino mass textures. Finally, we discuss direct ways to look for lepton-number violation in ultra-high energy neutrino interactions. 1. Neutrino data and Implications Recent reports by Super-Kamiokande [1] and othe