Revising neutrino oscillation parameter space with direct flavor-changing interactions - art. no. 113007

We formulate direct, neutrino flavor-changing interactions in a framework t hat fits smoothly with the parametrization of two- and three-state mixing o f massive neutrino states. We show that even small direct interaction stren gths could have important consequences on the interpretation of currently r unning and proposed oscillation experiments. The oscillation amplitude and the borders of the allowed regions in two- and three-flavor mixing paramete r space can be sensitive to the presence of direct interactions when the tr ansition probability is small. We use extensively the high sensitivity of t he NOMAD experiment to illustrate potentially large effects from small, dir ect flavor violation. In the purely leptonic sector, we find that the clean nu(mu) and nu(e) beams from a mu(+)-mu(-) collider could provide the sharp est tests of direct flavor violation.