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Abstract:

The production of dijets in diffractive deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 61 pb-1. The dijet cross section has been measured for virtualities of the exchanged virtual photon, 5 < Q2 < 100 GeV2, and γ*p centre-of-mass energies, 100 < W < 250 GeV. The jets, identified using the inclusive kT algorithm in the γ*p frame, were required to have a transverse energy E* T,jet > 4 GeV and the jet with the highest transverse energy was required to have E* T,jet > 5 GeV. All jets were required to be in the pseudorapidity range -3.5<η* jet<0. The differential cross sections are compared to leading-order predictions and next-to-leading-order QCD calculations based on recent diffractive parton densities extracted from inclusive diffractive deep inelastic scattering data. © 2007 Springer-Verlag / Società Italiana di Fisica.

Abstract:

We report the first measurements of inclusive W and Z boson cross-sections times the corresponding leptonic branching ratios for collisions at TeV based on the decays of the W and Z bosons into electrons and muons. The data were recorded with the CDF II detector at the Fermilab Tevatron and correspond to an integrated luminosity of 72.0 ± 4.3 pb-1. We test e-μ lepton universality in W decays by measuring the ratio of the W → μν to W → eν cross sections and determine a value of 0.991 ± 0.004(stat.) ± 0.011(syst.) for the ratio of W - ℓ - ν couplings (gμ/ge). Since there is no sign of non-universality, we combine our cross-section measurements in the different lepton decay modes and obtain σw × Br (pp̄ → W → ℓv) = 2.749 ± 0.010(stat.) ± 0.053(syst.) ± 0.165 (lum.) nb and σγ* × Br (pp̄ → γ*/Z → ℓℓ) = 254.9 ± 3.3(stat.) ± 4.6(syst.) ± 15.2(lum.) pb for dilepton pairs in the mass range between 66 GeV/c2 and 116 GeV/c2. We compute the ratio R of the W → ℓν to Z → ℓℓ cross sections taking all correlations among channels into account and obtain R = 10.84 ± 0.15(stat.) ± 0.14(syst.) including a correction for the virtual photon exchange component in our measured γ*/Z → ℓℓ cross section. Based on the measured value of R, we extract values for the W leptonic branching ratio, Br(W → ℓν)= 0.1082 ± 0.0022; the total width of the W boson, Γ(W)= 2092 ± 42 MeV; and the ratio of W and Z boson total widths, Γ(W)/Γ(Z)= 0.838 ± 0.017. In addition, we use our extracted value of Γ(W) whose value depends on various electroweak parameters and certain CKM matrix elements to constrain the Vcs CKM matrix element, |Vcs| = 0.976 ± 0.030. © 2007 IOP Publishing Ltd.

Abstract:

We present a study of the results obtained combining LO partonic matrix elements with different orders of partons distributions. These are compared to the best prediction using NLO for both matrix elements and parton distributions. The aim is to determine which parton distributions are most appropriate to use in those cases where only LO matrix elements are available, e.g. as in many Monte Carlo generators. Both LO and NLO parton distributions have faults so a modified optimal LO set is suggested.

Abstract:

In the past year, the Linear Collider Flavour Identification (LCFI) Collaboration has taken significant steps towards having a sensor suitable for use in the silicon vertex detector of the International Linear Collider (ILC). The goal of the collaboration is to develop the sensors, electronic systems and mechanical support structures necessary for the construction of a high performance vertex detector and to investigate the contribution such a vertex detector can make to the physics accessible at the ILC. Particular highlights include the delivery and testing of both a second-generation column parallel CCD (CP-CCD), design of the next-generation readout ASIC (CPR2a) and a dedicated ASIC for driving the CP-CCD. This paper briefly describes these and other highlights. (c) 2007 Elsevier B.V. All rights reserved.