Guy Wilkinson

Abstract:

An inclusive measurement of the average multiplicity of bb̄ pairs from gluons, gbb̄, in hadronic Z0 events collected by the DELPHI experiment at LEP, is presented. A counting technique, based on jet b-tagging in 4-jet events, has been used. Looking for secondary bottom production in events with production of any primary flavour, by requiring two b-tagged jets in well defined topological configurations, gave gbb̄ = (0.21 ± 0.11(stat) ± 0.09(syst))%. This result was checked with a different method designed to select events with four b quarks in the final state. Agreement within the errors was found.© 1997 Elsevier Science B.V.

Abstract:

The measurement of the correlation between the transverse spin components of τ+ τ- pairs collected during 1992 to 1994 with the DELPHI detector at LEP1 is presented. A value CTT = 0.87 ± 0.20 (stat.) +0.10-0.12 (syst.) was obtained for the correlation parameter, in agreement with the Standard Model expectation. © 1997 Published by Elsevier Science B.V.

Abstract:

A sample of about 1.4 million hadronic Z decays, selected among the data recorded by the DELPHI detector at LEP during 1994, was used to measure for the first time the momentum spectra of K+, K0, p, Λ and their antiparticles in gluon and quark jets. As observed for inclusive charged particles, the production spectra of identified particles were found to be softer in gluon jets than in quark jets, with a higher total multiplicity. © 1997 Published by Elsevier Science B.V.

Abstract:

Correlations between pions from different Ws in e+e- → W+W- events are studied using data collected by the DELPHI detector at LEP running at a centre-of-mass energy of 172 GeV in 1996. At the present level of statistics, no enhancement of the correlation function above that expected from a pair of uncorrelated W's is observed at small values of the four- momentum difference of the pions. © 1997 Published by Elsevier Science B.V.

Abstract:

The hadronic fragmentation functions of the various quark flavours and of gluons are measured in a study of the inclusive hadron production from Z0 decays with the DELPHI detector and are compared with the fragmentation functions measured elsewhere at energies between 14 GeV and 91 GeV. A large scaling violation is observed, which is used to extract the strong coupling constant from a fit using a numerical integration of the second order DGLAP evolution equations. The result is αs(Mz) = 0.1241+0.006-0.007(exp) ±0.009(theory) where the first error represents the experimental uncertainty and the second error is due to the factorization and renormalization scale dependence. © 1997 Elsevier Science B.V.