Combined Forward-Backward Asymmetry Measurements in Top-Antitop Quark Production at the Tevatron

The CDF and D0 experiments at the Fermilab Tevatron have measured the asymmetry between yields of forward- and backward-produced top and antitop quarks based on their rapidity difference and the asymmetry between their decay leptons. These measurements use the full data sets collected in proton-antiproton collisions at a center-of-mass energy of $\sqrt s =1.96$ TeV. We report the results of combinations of the inclusive asymmetries and their differential dependencies on relevant kinematic quantities. The combined inclusive asymmetry is $A_{\mathrm{FB}}^{t\bar{t}} = 0.128 \pm 0.025$. The combined inclusive and differential asymmetries are consistent with recent standard model predictions

Measurement of the muonic cross section times branching ratio of the W boson and Z boson, the muonic ratio of W boson to Z boson and extraction of the muonic branching fraction of W bosons and W boson width in proton-antiproton collisions at 1.8 TeV.

We analyze the production of high transverse momentum muons produced by the proton-antiproton colliding beams at the Fermilab Tevatron and detected by the Collider Detector at Fermilab. We measure the W and Z production cross sections times muon branching ratio at a pp center of mass energy of $\sqrt{s}$ = 1.8 TeV and determine: $\sigma(p\bar p\to W)\cdot B(W\to\mu\nu) = 2.521\pm 0.032(stat)\pm 0.106(syst)\pm 0.095(lum)\ nb$ and $\sigma(p\bar p\to Z)\cdot B(Z\to\mu\mu) = 0.1895\pm 0.0092(stat)\pm 0.0083(syst)\pm 0.0072(lum)\ nb$. The data set corresponds to an integrated luminosity of \int\ {\cal L} = 18.82\pm 0.68\ pb\sp{-1}. We also measure the ratio of these cross sections to be R\sb\mu = \sigma\cdot B(W\to\mu\nu)/\sigma\cdot B(Z\to\mu\mu) = 13.30\pm 0.67(stat)\pm 0.42(syst). From R\sb\mu, we extract a value for the W muonic branching ratio: $B(W\to\mu\nu) = \Gamma(W\to\mu\nu)/\Gamma(W) = 0.1345\pm 0.0068(stat)\pm 0.0045(syst)$ and the total W width: $\Gamma(W) = 1.689\pm 0.085(stat)\pm 0.057(syst)\ GeV$. We use the branching ratio to look for unknown decay modes of the W. We compare the cross sections and W width to the recent theory predictions.Ph.D.PhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/104254/1/9513295.pdfDescription of 9513295.pdf : Restricted to UM users only

Measurement of the D+D^+- Meson Production Cross Section at Low Transverse Momentum in ppˉp\bar{p} Collisions at s=1.96\sqrt{s}=1.96 TeV

International audienceWe report on a measurement of the D+-meson production cross section as a function of transverse momentum (pT) in proton-antiproton (pp¯) collisions at 1.96 TeV center-of-mass energy, using the full data set collected by the Collider Detector at Fermilab in Tevatron Run II and corresponding to 10  fb-1 of integrated luminosity. We use D+→K-π+π+ decays fully reconstructed in the central rapidity region |y|<1 with transverse momentum down to 1.5  GeV/c, a range previously unexplored in pp¯ collisions. Inelastic pp¯-scattering events are selected online using minimally biasing requirements followed by an optimized offline selection. The K-π+π+ mass distribution is used to identify the D+ signal, and the D+ transverse impact-parameter distribution is used to separate prompt production, occurring directly in the hard-scattering process, from secondary production from b-hadron decays. We obtain a prompt D+ signal of 2950 candidates corresponding to a total cross section σ(D+,1.5<pT<14.5  GeV/c,|y|<1)=71.9±6.8(stat)±9.3(syst)  μb. While the measured cross sections are consistent with theoretical estimates in each pT bin, the shape of the observed pT spectrum is softer than the expectation from quantum chromodynamics. The results are unique in pp¯ collisions and can improve the shape and uncertainties of future predictions