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 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.Measurement of the W boson polarization in top decay at CDF at s=1.8 TeV
Physical Review D American Physical Society (APS) 71:3 (2005) 031101
Abstract:
The polarization of the W boson in t→Wb decay is unambiguously predicted by the standard model of electroweak interactions and is a powerful test of our understanding of the tbW vertex. We measure this polarization from the invariant mass of the b quark from t→Wb and the lepton from W→lν whose momenta measure the W decay angle and direction of motion, respectively. In this paper we present a measurement of the decay rate (fV+A) of the W produced from the decay of the top quark in the hypothesis of V+A structure of the tWb vertex. We find no evidence for the nonstandard V+A vertex and set a limit on fV+A < 0.80 at 95% confidence level. By combining this result with a complementary observable in the same data, we assign a limit on fV+A < 0.61 at 95% CL. This corresponds to a constraint on the right-handed helicity component of the W polarization of f+<0.18 at 95% CL. This limit is the first significant direct constraint on fV+A in top decay.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)
Abstract:
We present the results of a search for anomalous production of diphoton events with large missing transverse energy using the Collider Detector at Fermilab. In 202 pb -1 of pp̄ collisions at √s = 1.96 TeV we observe no candidate events, with an expected standard model background of 0.27 ± 0.07(stat) ± 0.10(syst) events. The results exclude a lightest chargino of mass less than 167 GeV/c 2, and lightest neutralino of mass less than 93 GeV/c 2 at 95% C.L. in a gauge-mediated supersymmetry-breaking model with a light gravitino. © 2005 The American Physical Society.KS0 and Λ0 production studies in p(p)over-bar collisions at √s=1800 and 630 GeV - art. no. 052001
PHYSICAL REVIEW D 72:5 (2005) ARTN 052001