Neutrino Masses and Mixing

Abstract

The investigation of neutrino properties is a very important problem of today’s neutrino physics. The key problem is the problem of neutrino masses. If neutrinos are massive, they can be mixed. If the total lepton number is conserved, massive neutrinos are Dirac particles. If the neutrino masses are generated by an interaction that does not conserve the total lepton number, neutrinos with definite mass are Majorana particles. All this possibilities correspond to different gauge theories and it is very important that they can be distinguished experimentally. There are more than 60 different experiments that are going on at present on the search for effects of the masses, nature and mixing of neutrinos, and there is a general belief that investigation of neutrino properties could allow us to reach new physics. In this reports I will discuss: 1. possibilities of neutrino mixing. 2. neutrino oscillations in vacuum and in matter. 3. experimental indications in favor of neutrino masses and mixing. From all existing data it follows that flavor neutrinos νe, νμ and ντ interact with matter via standard CC and NC interactions