Analytical and semiclassical aspects of matter-enhanced neutrino oscillations

Matter-enhanced neutrino oscillations for the case of two neutrino flavors are studied and three different approximation methods for calculating the unaveraged oscillation probability are presented. Two of these methods provide simple analytical expressions, valid for small or large vacuum mixing angles, which are very simple to evaluate numerically. The third method provides an expression uniformly valid over the entire range of mixing angles. In their respective regions of validity, the approximate calculations using these methods are found to be in very good agreement with the exact calculations