Measurement of the tt̄ production cross section in pp̄ collisions at √s = 1.96 TeV using lepton + jets events with secondary vertex b -tagging
Physical Review D - Particles, Fields, Gravitation and Cosmology 71:5 (2005) 1-28
Abstract:
We present a measurement of the tt̄ production cross section using events with one charged lepton and jets from pp̄ collisions at a center-of-mass energy of 1.96 TeV. In these events, heavy flavor quarks from top quark decay are identified with a secondary vertex tagging algorithm. From 162 pb-1 of data collected by the Collider Detector at Fermilab, a total of 48 candidate events are selected, where 13.5 ± 1.8 events are expected from background contributions. We measure a tt̄ production cross section of 5.6Measurement of the Bs 0 lifetime in the exclusive decay channel Bs 0 → J/ψφ
Physical Review Letters 94:4 (2005)
Abstract:
Using the exclusive decay Bs0 → J/ψ (μ+μ-)φ (K+K-), we report the most precise single measurement of the Bs0 lifetime. The data sample corresponds to an integrated luminosity of approximately 220 pb-1 collected with the DO detector at the Fermilab Tevatron Collider in 2002-2004. We reconstruct 337 signal candidates, from which we extract the Bs0 lifetime, τ(Bs0) = 1.444-0.090+0.098(stat) ± 0.020(sys) ps. We also report a measurement for the lifetime of the B0 meson using the exclusive decay B0 → J/ψ(μ+μ-) K*0(&92)(K+π-). We reconstruct 1370 signal candidates, obtaining τ(B0) = 1.473 -0.050+0.052(stat)±0.023(sys) ps, and the ratio of lifetimes, τ(Bs0)/τ(B0) = 0.980 -0.0.710.076(stat) ± 0.003(sys). © 2005 The American Physical Society.Search for supersymmetry with gauge-mediated breaking in diphoton events at D0
Physical Review Letters 94:4 (2005)
Abstract:
We report the results of a search for supersymmetry (SUSY) with gauge-mediated breaking in the missing transverse energy distribution of inclusive diphoton events using 263 pb-1 of data collected by the DO experiment at the Fermilab Tevatron Collider in 2002-2004. No excess is observed above the background expected from standard model processes, and lower limits on the masses of the lightest neutralino and chargino of about 108 and 195 GeV, respectively, are set at the 95% confidence level. These are the most stringent limits to date for models with gauge-mediated SUSY breaking with a short-lived neutralino as the next-to-lightest SUSY particle. © 2005 The American Physical.Measurement of the J/ψ meson and b-hadron production cross sections in pp̄ collisions at √s = 1960 GeV
Physical Review D - Particles, Fields, Gravitation and Cosmology 71:3 (2005) 032001-1-032001-26
Abstract:
We present a new measurement of the inclusive and differential production cross sections of J/ψ mesons and b hadrons in proton-antiproton collisions at √s = 1960 GeV. The data correspond to an integrated luminosity of 39.7 pb-1 collected by the CDF run II detector. We find the integrated cross section for inclusive J/ψ production for all transverse momenta from 0 to 20 GeV/c in the rapidity range |y| < 0.6 to be 4.08 ± 0.02(Stat)-0.33 +0.36(syst) μb. We separate the fraction of J/ψ events from the decay of the long-lived b hadrons using the lifetime distribution in all events with pT(J/ψ) > 1.25 GeV/c. We find the total cross section for b hadrons, including both hadrons and antihadrons, decaying to J/ψ with transverse momenta greater than 1.25 GeV/c in the rapidity range |y(J/ψ)| < 0.6 is 0.330 ± 0.005(stat) -0.033 +0.036(syst) μb. Using a Monte Carlo simulation of the decay kinematics of b hadrons to all final states containing a J/ψ, we extract the first measurement of the total single b-hadron cross section down to zero transverse momentum at √s = 1960 GeV. We find the total single b-hadron cross section integrated over all transverse momenta for b hadrons in the rapidity range |y| < 0.6 to be 17.6 ± 0.4(stat) -2.3 +2.5(syst) μb. © 2005 The American Physical Society.Search for anomalous production of diphoton events with missing transverse energy at CDF and limits on gauge-mediated supersymmetry-breaking models
Physical Review D - Particles, Fields, Gravitation and Cosmology 71:3 (2005)