Evolution equations of neutrino mixing in matter

A set of rephasing invariant parameters for the neutrino mixing are introduced. Under this parametrization, the squared elements of the neutrino mixing matrix are found to satisfy a set of differential equations as functions of the induced mass. They show clearly the dominance of pole terms when the neutrino induced masses cross. It is found that these equations have very good approximate solutions for all values of the induced mass. The results may be applicable to extracting unknowns from the Long Baseline Experiments (LBL).