Guy Wilkinson

Abstract:

DELPHI (DEtector with Lepton, Photon and Hadron Identification) is a detector for e+e- physics, designed to provide high granularity over a 4π solid angle, allowing an effective particle identification. It has been operating at the LEP (Large Electron-Positron) collider at CERN since 1989. This article reviews its performance.

Abstract:

A search for pair production of the lightest chargino at √s = 130.4 and 136.3 GeV has been carried out using the data sample corresponding to the 5.92 pb-1 recorded by the DELPHI detector during the high energy run of LEP in the last period of 1995. The theoretical reference model has been the Minimal Supersymmetric Standard Model with R-parity conservation. The three topologies expected for the decay of a pair of charginos, namely two acoplanar leptons plus missing energy (ℓℓ), two jets and an isolated lepton plus missing energy (jjℓ) and missing energy in a hadronic environment (√s), were investigated. No evidence of a signal was found. Lower mass limits were derived for various scenarios, including the case of a low mass difference between the chargino and the neutralino and of a light sneutrino. The mass limits range between 56.3 GeV/c2 and the kinematic limit.

Abstract:

This letter reports the results of the measurement of single photon production in the reaction e+e- → γ+ invisible particles at centre-of-mass energies √s = 130 and 136 GeV and an integrated luminosity of 5.83 pb-1, collected with the DELPHI detector at LEP. The signal is compatible with the prediction of the Standard Model for the process e+e- → vv̄γ, and the number of neutrino families has been determined to be Nv, = 3.1 ± 0.6. Limits have been derived on anomalous neutral gauge boson couplings and on compositeness in the framework of a specific model.

Abstract:

During the last 1995 data acquisition period at LEP, the DELPHI experiment collected an integrated luminosity of 5.9 pb-1 at centre-of-mass energies of 130 GeV and 136 GeV. Radiative leptonic events (e, μ, τ) with high energy photons were studied and compared to Standard Model predictions. The data were used to search for charged excited leptons decaying through an electromagnetic transition. No significant signal was found. From the search for pair produced excited leptons, the limits me* > 62.5 GeV/c2, mμ* > 62.6 GeV/c2 and mτ* > 62.2 GeV/c2 at 95% confidence level were established. For single excited lepton production, upper limits on the ratio λ/mℓ* of the coupling of the excited charged lepton to its mass were derived.

Abstract:

The inclusive production of the f′2(1525) in hadronic Z0 decays has been studied in data collected by the DELPHI detector at LEP. The Ring Imaging Cherenkov detectors were important tools in the identification of the decay f′2(1525) → K+K-. The average number of f′2(1525) produced per hadronic Z decay, 〈f′2〉 = 0.020 ± 0.005 (stat) ± 0.006 (syst), and the momentum distribution of the f′2(1525) have both been measured. The mass and width of the f′2(1525) are found to be 〈M f′2〉 = 1535 ± 5 (stat) ± 4 (syst) MeV/c2, 〈Γ f′2〉 = 60 ± 20 (stat) ± 19 (syst) MeV/c2.