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

We report on further analysis of events with large missing transverse energy from 715 nb^-1 of data from the UA1 experiment at the CERN proton-antiproton collider. Measured W and Z⁰ 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) Z⁰ 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/c² (90% CL) and a limit on the number of additional neutrino species of n≤7 (90% CL).