SEARCH FOR HEAVY NEUTRINO DECAYS IN THE BEBC BEAM DUMP EXPERIMENT

New limits on lepton mixing parameters are derived from a search for decays of heavy neutrinos in a proton beam dump experiment. The limits |Uøi|2, |Uei|2 < 10-6-10-7 are obtained for neutrino mass eigenstates vi 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 |Uøi|2 for neutrino masses greater than 0.5 GeV. For the mass eigenstate v3 in particular, we obtain the limits |Uø3|2 < 10-7-10-8, |Ue3|2 < 10-9-10-10 for the mass range 150-190 MeV, assuming the v3 to be produced directly in charmed F meson decays. © 1985