Peter Renton

Abstract:

From the Z decays recorded in 1994 and 1995 by the DELPHI detector at LEP, the charged particle multiplicity of weakly decaying B hadrons was measured to be: 4.97 ± 0.03 ± 0.06 excluding the K o and A decay products. © 1998 Published by Elsevier Science B.V. All rights reserved.

Abstract:

Trilinear gauge boson couplings are measured using data taken by DELPHI at 161 GeV and 172 GeV. Values for WWV couplings (V = Z,γ) are determined from a study of the reactions e⁺e^-→ W⁺W^- and e⁺e^- → Wev, using differential distributions from the WW final state in which one W decays hadronically and the other leptonically, and total cross-section data from other channels. Limits are also derived on neutral ZVγ couplings from an analysis of the reaction e⁺e^-→ y + invisible particles. © 1998 Elsevier Science B.V.

Abstract:

This paper presents results on charged Higgs boson production, based on LEP data collected at √s = 172 GeV, that complement the previous DELPHI results obtained at centre of mass energies up to 161 GeV. The charged Higgs bosons are assumed to be pair produced and to decay either into a quark pair or into τVτ. The three different possible final states are included in the analysis. Data from ring imaging Cherenkov and microvertex detectors are used to identify the quarks as a cs pair. The number of candidates found is compatible with the background expected from standard processes. Combining the results of the present analysis with those of the previous analysis at lower energies, a new lower mass limit for the charged Higgs boson is set at 54.5 GeV/c². © 1998 Elsevier Science B.V.

Abstract:

The value of the b quark mass at the M2 scale defined in the MS renormalization scheme, mb(MZ), was determined using 2.8 million hadronic Z decays collected during 1992-1994 by the DELPHI detector to be mb(MZ) = 2.67 ± 0.25 (stat.) ± 0.34 (frag.) ± 0.27 (theo.) GeV/c². The analysis considers NLO corrections to the three-jet production rate including mass effects, and the result obtained agrees with the QCD prediction of having a running b quark mass at an energy scale equal to MZ. This is the first time that such a measurement is performed far above the bb̄ production threshold. The study also verifies the flavour independence of the strong coupling constant for b and light quarks within 1% accuracy. © 1998 Elsevier Science B.V.

Abstract:

The W mass and QCD working group discussed a wide variety of topics relating to present and future measurements of M-W at LEP2, including QCD backgrounds to W+W- production. Particular attention was focused on experimental issues concerning the direct reconstruction and threshold mass measurements, and on theoretical and experimental issues concerning the ii-jet final state. This report summarizes the main conclusions.