General RG equations for physical neutrino parameters and their phenomenological implications

The neutral leptonic sector of the Standard Model presumably consists of th ree neutrinos with non-zero Majorana masses with properties further determi ned by three mixing angles and three CP-violating phases. We derive the gen eral renormalization group equations for these physical parameters and appl y them to study the impact of radiative effects on neutrino physics. In par ticular, we examine the existing solutions to the solar and atmospheric neu trino problems, draw conclusions on their theoretical naturalness, and show how some of the measured neutrino parameters could be determined by purely radiative effects, For example, the mass splitting and mixing angle sugges ted by solar neutrino data could be entirely explained as a radiative effec t if the small, angle MSW solution is realized. On the other hand, the mass splitting required by atmospheric neutrino data is probably determined by unknown physics at a high energy scale. We also discuss the effect of non-z ero CP-violating phases on radiative corrections. (C) 2000 Elsevier Science B.V. All rights reserved.