Four-neutrino mixing and long-baseline neutrino oscillation experiments

We consider the two schemes with four massive neutrinos which are compatible with the results of all neutrino oscillation experiments. We show that in these two schemes the probabilities of ν̄e disappearance and (−) νμ→ (−) νe appearance in long-baseline experiments are strongly suppressed. The investigation of neutrino properties, in particular of neutrino masses and mixing, is one of the most important problems in today’s high-energy physics and many experiments are dedicated to it. Among the numerous existing experimental results there are three positive indications which come from neutrino oscillation experiments. Neutrino oscillations can occur only if neutrinos are massive particles, if their masses are different and if neutrino mixing is realized in nature [1]. In this case, the left-handed flavor neutrino fields ναL (α = e, μ, τ) are superpositions of the left-handed components νkL (k = 1, . . . , n) of the fields of neutrinos with definite masses mk: ναL = n ∑