Events with large missing transverse energy at the cern collider: II. search for the decays of W± into heavy leptons and of Z0 into non-interacting particles

Abstract We report on further analysis of events with large missing transverse energy from 715 nb −1 of data from the UA1 experimentat the CERN proton- antiprotoncollider. Measured W and Z 0 rates and heavy flavour cross sections are used to predict rates of missing transverse energy event from all known standard model process. Limits are derived on two possible new sources, namely: (1) semi-hadronic decays of a fourth sequential charged heavy lepton coupling to the W boson, (2) Z 0 decays into additional pairs of non-interacting particles. After taking into additional pairs of non-interacting particles. After taking into account all known sources of missing transverse energy events, we find a mass limit on a fourth-generation charged lepton of m L >41 GeV / c 2 (90% CL) and a limit on the number of additional neutrino species of n ⩽7 (90% CL).