A Study of J/psi Production at the LEP $e^{+} e{-}$ Collider; and the Implementation of the DELPHI Slow Controls System

This thesis describes two separate areas of work conducted for the DELPHI detector at LEP. The first concerns the Slow Controls of the DELPHI detector, which enable a single operator to oversee the proper functioning of the apparatus and to diagnose faults as they occur. The hardware and software of this system, as well as their interface to the experiment and the operator, are described. Some conclusions are drawn from seven years' design work and the initial six years' operation of DELPHI. Secondly, a study is made of the production, at e+e- collision centre of mass energies close to the Z0 resonance, of J/psi mesons, decaying to mu+ mu-. J/psi mesons produced via a B-hadron are used to measure the mean B lifetime, tau_B = (1.53 +- 0.11 (stat.) +- 0.06 (syst.)) ps A measurement is also made of the fraction of J/psis produced promptly at the e+e- collision point, N(Z0 -> prompt J/psi X) / N(Z0 -> J/psi X) = (9.6 +- 3.2 (stat.) +- 1.2 (syst.))%. This method is largely model-independent.