This award is to support research done by a number of principal investigators at the University of Chicago for a three year period. Projects covered by the proposal fall into four main groups. The first of these is concerned with three experiments at Fermilab focussing on neutral K meson decays to determine parameters appropriate to CP and to CPT violation, and to study rare K decays. The second group studies very high energy proton antiproton annihilations using the Tevatron Collider Detector Facility (CDF), also at Fermilab. Important goals of this experiment include the determination of the mass of the W boson and also limits on the mass of the illusive t quark which has so far evaded all attempts at observation. A third group uses the OPAL spectrometer at the LEP accelerator at CERN to study decays of Z bosons. The Z results are completely complementary to those of the CDF experiment in understanding the standard model, and any flaws that may exist in it. The fourth group is in an experiment aimed at a search for decays of stopping muons, produced at the Los Alamos facility LAMPF, to positronphoton pairs. Flavour changing decays of leptons, of which such events would be an example, have never been observed. The standard model predicts no such decays.