Charged lepton beams as a source of effective neutrinos

Neutrinos are likely the most poorly understood basic constituents of the Standard Model. In order to investigate precisely their interactions one should be able to create high intensity and well-collimated neutrino beams with known flavor compositions. This is a challenging problem for neutrino experiments. We propose a method of studying neutrino interactions based on the fact that a charged lepton is able to manifest itself effectively, with a certain probability, as a neutrino. The effective neutrino method may provide an additional tool for probing neutrino-induced reactions at $e^+e^-$ and $ep$ colliders as well as at other facilities that use charged lepton beams. We derive the distributions of the effective neutrinos in the charged leptons and give examples of application of the method to electron-positron collisions.