1. Particle Physics Seminar

    "Evidence of s-channel single top quark production at DØ"

    Presented by Jyoti Joshi, University of California Riverside

    Thursday, July 18, 2013, 3 pm
    Small Seminar Room, Bldg. 510

    Hosted by: Marc-Andre Pleier

    We present a new measurement of the electroweak single top quark production cross section in proton-antiproton collisions at center-of-mass energy of 1.96 TeV using data corresponding to 9.7 fb-1 of integrated luminosity collected by the DØ detector. At the Tevatron, the electroweak production of top quarks proceeds mainly via the decay of a time-like virtual W boson accompanied by a bottom quark in the s-channel or via the exchange of a space-like virtual W boson between a light quark and a bottom quark in the t-channel. We select signal-like events, containing one energetic electron or muon, an imbalance in transverse momentum, and two or three jets, with one or two identified as candidates for originating from the fragmentation of b quarks. Multivariate analysis techniques are used to discriminate between signal and background. We measure a cross section compatible with the Standard Model prediction for electroweak production of single top and use it directly to measure the limit on CKM matrix element |Vtb|.