HADRON PRODUCTION FROM e + e - COLLISIONS AROUND THE Z ' MASS

The properties of the Z' particle are studied with hadronic events taken by the L3 detector at LEP. 14,352 events at ten different center of mass energies are used to calculate the hadronic cross section. From a fit to the Z0 resonance line shape, the Z0 mass, total width, and the hadronic cross section are measured to be Mz = 91.14 0.025(experiment) 0.030(LEP) GeV, I7z = 2.529 0.053 GeV and Ch(Mz) = 29.5 0.7nb. rinvisible is also fitted to be 0.548 0.029GeV, corresponds to 3.30 0.18 species of light neutrinos. The possibility of four or more neutrino flavors is ruled out at 4a confidence level. The production of b-hadrons is studied through their semi-leptonic decay. A sample of 80% b-event purity is selected. With this sample, the partial width of Zo -bb decay is measured to be 356.8 50MeV. The charge asymmetry at Zo peak is measured to be 18.8 13.9%. Thesis Supervisor: Samuel C. C. Ting Title: Thomas Dudley Cabot Institute Professor of Physics