LHCb

Abstract:

The average lifetime of B hadrons was measured using data collected with the DELPHI detector at the LEP collider during 1991 and 1992. The measurement was performed using two different anayses. The first method was an improvement on a previous technique, which used charged particle impact parameter distributions. This analysis measured an average lifetime for B hadrons of {Mathematical expression} The second method was based on a new technique, which used inclusively reconstructed secondary vertices to measure {Mathematical expression} Taking into account both the statistical and systematic corelations, the results of these two methods were combined to give an average lifetime for B hadrons of {Mathematical expression} © 1994 Springer-Verlag.

Abstract:

Two-particle correlations in invariant mass are studied separately for like-sign and unlike-sign pions. Strong correlations are observed only at small masses. The correlations decrease very rapidly for like-sign pions and slowly for unlike-sign pions, manifesting different particle dynamics. The like-sign correlations exhibit a power-law behaviour as a function of mass, compatible with the previously observed intermittency effect. The predictions of the parton shower model (JETSET 7.3) deviate significantly from the data. However, good agreement is obtained with the mass correlations, both for the unlike-sign and for the like-sign pairs if the production of the η′ and ρ0 mesons is reduced and Bose-Einstein correlations are included in the model. The value of the Bose-Einstein correlation strength is consistent with unity for pions which are produced directly or in the decays of short-lived resonances. © 1994 Springer-Verlag.

Abstract:

Jets in photoproduction events have been studied with the ZEUS detector for γp centre-of-mass energies ranging from 130 to 250 GeV. The inclusive jet distributions give evidence for the dominance of resolved photon interactions. In the di-jet sample the direct processes are for the first time clearly isolated. Di-jet cross sections for the resolved and direct processes are given in a restricted kinematic range. © 1994.

Abstract:

The mechanical, electrical and electronic design and construction of the ZEUS central tracking detector are described, together with the chamber monitoring and environmental control. This cylindrical drift chamber is designed for track reconstruction, electron identification and fast event triggering in a high beam-crossing rate, high magnetic field application. © 1994.

Abstract:

The study of the properties of inclusive production of Ds mesons and of events in which a φ{symbol} and a muon are present in the same jet provides two independent measurements of the probability, fsw, for a heavy quark to hadronize into a strange B or D meson. The data sample analysed corresponds to 243,000 hadronic Z0 decays. The combined value of these measurements is fsw=0.19±0.06±0.08. From the flight distance distributions of Ds and of (φ{symbol}-lepton) secondary vertices, with the lepton emitted at high transverse momentum relative to the jet axis, two values are obtained for the Bs0 meson lifetime. Combining these measurements with a previous result based on the study of Ds-μ events, the Bs0 meson lifetime is measured to be: 0.96±0.37 ps. © 1994 Springer-Verlag.