Friday 25 November 2011, 11:15h, at CWI/Nikhef in Z011
This colloquium is part of the "Landelijk Seminarium @ Z011"
Speaker: Guido Altarelli (CERN/Roma Tre)
Title: Neutrino mass and mixing: lessons and challenges
Abstract:
In the last years we have learnt a lot about neutrino masses and mixings. Neutrinos are not all massless but their masses are very small. Probably masses are small because neutrinos are Majorana particles with masses inversely proportional to the large scale M of lepton number (L) violation, which turns out to be compatible with the GUT scale. We have understood there there is no contradiction between large neutrino mixings and small quark mixings, even in the context of GUTs and that neutrino masses fit well in the SUSY GUT picture. Out of equilibrium decays with CP and L violation of heavy RH neutrinos can produce a B-L asymmetry, then converted near the weak scale by instantons into an amount of B asymmetry compatible with observations (baryogenesis via leptogenesis). It has been established that active neutrinos are not a significant component of Dark Matter in the Universe. A long list of models have been formulated over the years to understand neutrino masses and mixings. With the continuous improvement of the data most of the models have been discarded by experiment. Still the surviving models span a wide range going from a maximum of symmetry, with discrete non abelian flavour groups, to the opposite extreme of anarchy.
link naar colloquia pagina