Search for heavy neutrino decays in the BEBC beam dump experiment

Abstract

New limits on lepton mixing parameters are derived from a search for decays of heavy neutrinos in a proton beam dump experiment. The limits | U øi | 2, | U e i | 2 < 10 −6−10 −7 are obtained for neutrino mass eigenstates v i of mass between 0.5 and 1.75 GeV, which can be produced through mixing in charmed D meson decays. This is the first such limit on | U ø i| 2 for neutrino masses greater than 0.5 GeV. For the mass eigenstate v 3 in particular, we obtain the limits | U ø3 | 2 < 10 −7−10 −8, | U e3 | 2 < 10 −9−10 −10 for the mass range 150–190 MeV, assuming the v 3 to be produced directly in charmed F meson decays.