Neutrino Physics: Status and Prospects

Abstract

Solar and atmospheric neutrino data strongly indicate the need for physics beyond the Standard Model. The simplest, but not unique, interpretation of the data is in terms of neutrino oscillations. I summarize the results of the latest three-neutrino global analysis of the neutrino data, in particular the bounds on the angle θ ₁₃ probed in reactor experiments. Even though not implied by the data, bi-maximal neutrino mixing emerges as an attractive possibility, posing a challenge for unified theories of neutrino mass. I give a brief overview of the theoretical alternatives to generate bi-maximal or bi-large leptonic mixing inspired on the idea of Unification, which typically employ either a see-saw mechanism or high dimension operators, with or without family symmetries. They can lead to either hierarchical or quasi-degenerate neutrino mass spectra. Supersymmetric with bilinear breaking of R—parity provides a simple bottom-up-type model which allows to probe neutrino mixing also within the context of high—energy collider experiments such as the LHC. Reconciling solar, atmospheric and reactor data with the LSND hint requires a light sterile neutrino, a possibility which can be probed at neutral-current-sensitive solar & atmospheric neutrino experiments. Alternative interpretations of the solar neutrino data exist, consistent with the atmospheric data, such as resonant spin flavor precessions of υ _e .