Properties of the neutrino mixing matrix

For neutrino mixing we propose to use the parameter set X _i (={pipe}V _ei{pipe}²) and Ω _i (=ε{lunate} _ijk{pipe}V _μj{pipe}²{pipe}V _τk{pipe}²), with two constraints. These parameters are directly measurable since the neutrino oscillation probabilities are their quadratic functions. Physically, the set Ω _i signifies a quantitative measure of μ-τ asymmetry. Available neutrino data indicate that all the Ω _is are small (<O(10^-1)), but with large uncertainties. The behavior of Ω _i as functions of the induced neutrino mass in matter is found to be simple, which should facilitate the analyses of long baseline experiments.