Professor Brian Foster OBE, FRS

Abstract:

We present a measurement of time-dependent CP-violating asymmetries in neutral B meson decays collected with the BABAR detector at the PEP-II asymmetric-energy e+e-collider at the Stanford Linear Accelerator Center. The data sample consists of 29.7 fb-1recorded at the Υ(4S) resonance and 3.9 fb-1off resonance. One of the neutral B mesons, which are produced in pairs at the Υ(4S), is fully reconstructed in the CP decay modes J/ΨKS0, Ψ(2S)KS0, Xc1KS0, J/ΨK*0(K*0→Ks0π0) and J/ΨKL0, or in flavor-eigenstate modes involving D(*)π/ρ/a1and J/ΨK*0(K*0→K+π-). The flavor of the other neutral B meson is tagged at the time of its decay, mainly with the charge of identified leptons and kaons. A neural network tagging algorithm is used to recover events without a clear lepton or kaon tag. The proper time elapsed between the decays is determined by measuring the distance between the decay vertices. Wrong-tag probabilities, the time-difference resolution function, and the B0-B̄0oscillation frequency Δmdare measured with a sample of about 6350 fully-reconstructed B0decays in hadronic flavor-eigenstate modes. A maximum-likelihood fit to this flavor eigenstate sample finds Δmd=0.516±0.016(stat)±0.010(syst) ps-1. The value of the asymmetry amplitude sin 2Β is determined from a simultaneous maximum-likelihood fit to the time-difference distribution of the flavor-eigenstate sample and about 642 tagged B0decays in the CP-eigenstate modes. We find sin 2Β=0.59 ±0.14(stat)±0.05(syst), demonstrating that CP violation exists in the neutral B meson system. We also determine the value of the CP violation parameter |λ|=0.93±0.09(stat)±0.03(syst), which is consistent with the expectation of |λ|=1 for no direct CP violation.

Abstract:

Cross sections for e- p charged current deep inelastic scattering have been measured at a centre-of-mass energy of 318 GeV with an integrated luminosity of 16.4 pb-1 using the ZEUS detector at HERA. Differential cross sections dσ/dQ2, dσ/dx and dσ/dy are presented for Q2 > 200 GeV2. In addition, d2σ/(dxdQ2) was measured in the kinematic range 280 GeV2 < Q2 < 30 000 GeV2 and 0.015 < × < 0.42. The predictions of the Standard Model agree well with the measured cross sections. The mass of the W boson, determined from a fit to dσ/dQ2, is MW = 80.3±2.1(stat.) ± 1.2(syst.) ± 1.0(PDF) GeV. © 2002 Published by Elsevier Science B.V.

Abstract:

The exclusive photoproduction of J/ψ mesons, γp → J/ψp, has been studied in ep collisions with the ZEUS detector at HERA, in the kinematic range 20 < W < 290 GeV, where W is the photon-proton centre-of-mass energy. The J/ψ mesons were reconstructed in the ninon and the electron decay channels using integrated luminosities of 38 pb^-1 and 55 pb^-1, respectively. The helicity structure of J/ψ production shows that the hypothesis of s-channel helicity conservation is satisfied within two standard deviations. The total cross section and the differential cross-section dσ/dt, where t is the squared four-momentum transfer at the proton vertex, are presented as a function of W, for |t| < 18 Ge². The t distribution exhibits an exponential shape with a slope parameter increasing logarithmically with W with a value b = 4.15 ± 0.05(stat.)-0.18 ^+0.30(syst.) GeV^-2 at W = 90 GeV. The effective parameters of the Pomeron trajectory are αℙ(0) = 1.200 ± 0.009(stat.) -0.010 ^+0.004(Syst.) and α′ℙ = 0.115 ± 0.018(stat.)-0.015 ^+0.008(syst.) GeV^-2.

Abstract:

The measurement of B⁰ lifetime with partially reconstructed B⁰→D^-ℓ⁺νℓ decay was presented. The statistical error of the validation was included in the background systematic error. Results showed that the final relative error of ±1.9% was found by adding in quadrature the uncertainties from the sources.