Guy Wilkinson

Abstract:

Distributions of event shape variables obtained from 120600 hadronic Z decays measured with the DELPHI detector are compared to the predictions of QCD based event generators. Values of the strong coupling constant αs are derived as a function of the renormalization scale from a quantitative analysis of eight hadronic distributions. The final result, αs(MZ), is based on second order perturbation theory and uses two hadronization corrections, one computed with a parton shower model and the other with a QCD matrix element model. © 1992 Springer-Verlag.

Abstract:

The spectra of prompt electrons and muons from the semi-leptonic decays of heavy hadrons produced in Z0 decays have been used to measure the coupling of the Z0 to b quarks weighted by the B hadrons mean semi-leptonic branching fraction, giving a value: {Mathematical expression}. The data has also been used to measure the value of the fragmentation parameter, defined in the context of the LUND PS Model, version 7.2, giving: {Mathematical expression}. The corresponding value of the mean fraction of the beam energy taken by a B hadron in the fragmentation of a b quark is: {Mathematical expression}. If the values of {Mathematical expression} and ΓH are taken from the Standard Model, the following value is obtained for the mean semi-leptonic braching fraction of B hadrons: BRslb=(10.1±0.7)%. Taking the value of {Mathematical expression} from an independent analysis of DELPHI data based on the use of the boosted sphericity product, a value: BRslb=(10.1±1.3)% is obtained. © 1992 Springer-Verlag.

Abstract:

Using a data sample of 115000 hadronic Z0 decays, a search was performed for the production of excited charged leptons decaying into an ordinary lepton and one photon. Pair production of excited leptons of mass below 45 GeV/c2 is excluded. From an analysis of the lepton-photon mass spectra this experiment is also able to exclude single production of these particles for masses that reach up to 85 GeV/c2, if the compositeness scale is below 1 TeV. © 1992 Springer-Verlag.

Abstract:

A strong increase of the mean transverse momentum 〈pt〉 with the number of charged particles nch is observed in e+e - annihilations into hadrons at LEP energies. The effect resembles correlations observed in hadron-hadron interactions. In e+e- annihilations the 〈Pt〉 and nch correlations can be accounted for by gluon radiation. © 1992.

Abstract:

An analysis of the production of strange particles from the decays of the Z0 boson into multihadronic final states is presented. The analysis is based on about 90 000 selected hadronic Z0 decays collected by the DELPHI detector at LEP in 1990. Ks0, K*±, Λ(Λ) and Ξ- (Ξ+) have been identified by their characteristic decays. The measured production cross sections are compared with predictions of the Lund Monte Carlo tuned to data at PEP/PETRA energies. © 1992.