Guy Wilkinson

Abstract:

The cross sections for the production of single charged and neutral intermediate vector bosons were measured using integrated luminosities of 52 pb^-1 and 154 pb^-1 collected by the experiment at centre-of-mass energies of 182.6 GeV and 188.6 GeV, respectively. The cross sections for the reactions were determined in limited kinematic regions. The results found are in agreement with the Standard Model predictions for these channels. © 2001 Elsevier Science B.V.

Abstract:

A new precise measurement of |Vcb| and of the branching ratio BR(B̄⁰ → D*⁺ℓ^-v̄ℓ) has been performed using a sample of about 5000 semileptonic decays B̄⁰ → D*⁺ℓ^-v̄ℓ, selected by the DELPHI detector at LEP I by tagging the soft pion from D*⁺ → D⁰π⁺. The results are: Vcb = (39.0 ± 1.5 (stat.)-2.6^+2.5 (syst. exp.) ± 1.3 (syst. th.)) × 10^-3, BR(B̄⁰ → D*⁺ℓ^-v̄ℓ) = (4.70 ± 0.13 (stat.)-0.31^+0.36 (syst. exp.))%. The analytic dependencies of the differential cross-section and of the Isgur-Wise form factor as functions of the variable w = vB0 · vD* have also been obtained by unfolding the experimental resolution. © 2001 Published by Elsevier Science B.V.

Abstract:

Higgs bosons predicted by the fermiophobic scenario within Two Higgs Doublets Models were searched for in the data collected by the DELPHI detector at centre-of-mass energies between 189 GeV and 202 GeV, corresponding to a total integrated luminosity of 380 pb-1. No signal was found and confidence limits were derived in the framework of possible extensions of the Standard Model Higgs sector. © 2001 Elsevier Science B.V.

Abstract:

Searches for pair production of gauginos and squarks in e⁺e^- collisions at a centre-of-mass energy of 189 GeV have been performed on data corresponding to an integrated luminosity of 158 pb^-1 collected by the DELPHI detector at LEP. The data were analyzed under the assumption of non-conservation of R-parity through a single dominant Ū D̄ D̄ coupling between squarks and quarks. Typical final states contain between 4 and 10 jets with or without additional leptons. No excess of data above Standard Model expectations was observed. The results were used to constrain domains of the MSSM parameter space and derive limits on the masses of supersymmetric particles. The following mass limits at 95% CL were obtained from these searches: neutralino mass: mx̃1/⁰ ≥ 32 GeV; chargino mass: mx̃1/⁺ ≥ 94 GeV; stop and sbottom mass (indirect decay) with δAM > 5 GeV: mt̃1 ≥ 74 GeV for φmix = 0 rad, mt̃1 ≥ 59 GeV for φmix = 0.98 rad, mb̃1 ≥ 72 GeV for φmix = 0 rad. The angle φmix is the mixing angle between left and right handed quarks. © 2001 Elsevier Science B.V.

Abstract:

Searches for the Standard Model Higgs boson have been performed in the data collected by the DELPHI experiment at LEP in the year 2000 at centre-of-mass energies between 200 and 209 GeV corresponding to a total integrated luminosity of 224 pb-1. No evidence for a Higgs signal is observed in the kinematically accessible mass range, and a 95% CL lower mass limit of 114.3 GeV/c2 is set, to be compared with an expected median limit of 113.5 GeV/c2 for these data. © 2001 Elsevier Science B.V.