Xing, ZZ (reprint author), Inst High Energy Phys, Div Theory, POB 918, Beijing 100039, Peoples R China.
We introduce the commutators of lepton mass matrices to describe the phenomenon of lepton flavor mixing, and establish their relations to the effective Hamiltonians responsible for the propagation of neutrinos. The determinants of those commutators an invariant under matter effects, leading to an instructive relationship between the universal CP-violating parameters in vacuum and in matter. in the scenario of low-energy (100 MeV less than or equal toE less than or equal to1 GeV) and medium-baseline (100 km less than or equal toL less than or equal to 400 km) neutrino experiments, we illustrate the features of lepton flavor mixing and CP violation. The terrestrial matter effects on CP- and T-violating asymmetries in nu (e) <-> nu (mu) and <()over bar>(e) <-> <()over bar>(mu) neutrino oscillations are also discussed. We demonstrate that a relatively pure signal of leptonic CP violation at the percent level can be established from such medium-baseline experiments with low-energy neutrino beams.