Dynamical mixing angle method in neutrino oscillation in matter

Abstract

The general feature of the MSW effect, the enhanced oscillation of neutrino in matter, is discussed in two ways: the effective mass eigenstate method and $\it dynamical mixing angle$ method. Using a general neutrino survival probability which can be derived with the introduction of the dynamical mixing angles, an exact level-crossing transition probability in the non-adiabatic MSW effect is calculated. It is shown that the exact transition probability significantly differs from the Landau-Zener transition probability, usually derived based on the WKB method, when the vacuum mixing angle becomes large.