Comparison of three-jet events in pp̄ collisions at √s = 1.8 TeV to predictions from a next-to-leading order QCD calculation
Physical Review D - Particles, Fields, Gravitation and Cosmology 71:3 (2005) 032002-1-032002-12
Abstract:
The properties of three-jet events with total transverse energy greater than 320 GeV and individual jet energy greater than 20 GeV have been analyzed and compared to absolute predictions from a next-to-leading order (NLO) perturbative QCD calculation. These data, of integrated luminosity 86 pb -1, were recorded by the CDF Experiment for pp collisions at √s = 1.8 TeV This study tests a model of higher order QCD processes that result in gluon emission and may give some indication of the magnitude of the contribution of processes higher than NLO. The total cross section is measured to be 466 ± 3(stat.)-70 +207(syst.) pb. The differential cross section is furthermore measured for all kinematically accessible regions of the Dalitz plane, including those for which the theoretical prediction is unreliable. While the measured cross section is consistent with the theoretical prediction in magnitude, the two differ somewhat in shape in the Dalitz plane. © 2005 The American Physical Society.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.Measurement of the W boson polarization in top decay at CDF at √s = 1.8 TeV
Physical Review D - Particles, Fields, Gravitation and Cosmology 71:3 (2005) 031101-1-031101-7
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 (f V+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. © 2005 The American Physical Society.Search for electroweak single-top-quark production in pp̄ collisions at √s = 1.96 TeV
Physical Review D - Particles, Fields, Gravitation and Cosmology 71:1 (2005) 012005-1-012005-7
Abstract:
We report on a search for standard model t-channel and s-channel single-top quark production in pp̄ collisions at a center of mass energy of 1.96 TeV. We use a data sample corresponding to 162 pb-1 recorded by the upgraded collider detector at Fermilab. We find no significant evidence for electroweak top quark production and set upper limits at the 95% confidence level on the production cross section, consistent with the standard model: 10.1 pb for the t-channel, 13.6 pb for the s-channel and 17.8 pb for the combined cross section of t- and s-channel. © 2005 The American Physical Society.Measurement of partial widths and search for direct CP violation in $D^0$ meson decays to $K^- K^+$ and $π^- π^+$
Phys. Rev. Lett. 94 (2005) 122001-122001