A two parameter four neutrino mixing model with an exchange symmetry of the mass doublet neutrinos

In a model with four neutrino mass eigenstates grouping in two narrow doublets the condition of maximal mixing of the doublet neutrino components leads to a simple 4-neutrino mixing matrix which is related to two connected effective two-neutrino mixing patterns. As a result, large values of the neutrino oscillation amplitudes for both the solar and atmospheric neutrino anomalies appear quite naturally if the LSND data are accepted. The main predictions of the model, the , are in agreement with the new positive Super-Kamiokande data.