Search for Gluino-Mediated Bottom Squark Production in pp[over ] Collisions at sqrt[s]=1.96 TeV.
Phys Rev Lett 102:22 (2009) 221801
Abstract:
We report on a search for the supersymmetric partner of the bottom quark produced from gluino decays in data from 2.5 fb;{-1} of integrated luminosity collected by the Collider Detector at Fermilab at sqrt[s]=1.96 TeV. Candidate events are selected requiring two or more jets and large missing transverse energy. At least two of the jets are required to be tagged as originating from a b quark to enhance the sensitivity. The results are in good agreement with the prediction of the standard model processes, giving no evidence for gluino decay to bottom squarks. This result constrains the gluino-pair-production cross section to be less than 40 fb at 95% credibility level for a gluino mass of 350 GeV/c;{2}.Search for new particles decaying into dijets in proton-antiproton collisions at s=1.96TeV
Physical Review D - Particles, Fields, Gravitation and Cosmology 79:11 (2009)
Abstract:
We present a search for new particles which produce narrow two-jet (dijet) resonances using proton-antiproton collision data corresponding to an integrated luminosity of 1.13fb-1 collected with the CDFA II detector. The measured dijet mass spectrum is found to be consistent with next-to-leading-order perturbative QCD predictions, and no significant evidence of new particles is found. We set upper limits at the 95% confidence level on cross sections times the branching fraction for the production of new particles decaying into dijets with both jets having a rapidity magnitude |y| <1. These limits are used to determine the mass exclusions for the excited quark, axigluon, flavor-universal coloron, E6 diquark, color-octet techni-ρ, W′, and Z′. © 2009 The American Physical Society.Direct measurement of the W production charge asymmetry in pp collisions at square root s=1.96 TeV.
Phys Rev Lett 102:18 (2009) 181801
Abstract:
We present the first direct measurement of the W production charge asymmetry as a function of the W boson rapidity yW in pp collisions at sqrt[s]=1.96 TeV. We use a sample of W-->enu events in data from 1 fb-1 of integrated luminosity collected using the CDF II detector. In the region |yW|<3.0, this measurement is capable of constraining the ratio of up- and down-quark momentum distributions in the proton more directly than in previous measurements of the asymmetry that are functions of the charged-lepton pseudorapidity.Measurement of W-boson helicity fractions in top-quark decays using cos θ*
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 674:3 (2009) 160-167
Abstract:
Fully reconstructed t over(t, ̄) → W+ b W- over(b, ̄) → ℓ ν q over(q, ̄)′ b over(b, ̄) events are used to determine the fractions of right-handed (f+) and longitudinally polarized (f0) W bosons produced in top-quark decays. The helicity fractions are sensitive to the couplings and the Dirac structure of the Wtb vertex. This Letter reports measurements of the W-boson helicity fractions from two different methods using data corresponding to an integrated luminosity of 1.9 fb- 1 of p over(p, ̄) collisions at a center-of-mass energy of 1.96 TeV collected by the CDF II detector operating at the Fermilab Tevatron. Combining the results from the two methods, we find f0 = 0.62 ± 0.10 (stat) ± 0.05 (syst) under the assumption that f+ = 0, and f+ = - 0.04 ± 0.04 (stat) ± 0.03 (syst) with f0 fixed to the theoretically expected value of 0.70. Model-independent fits are also performed and simultaneously determine f0 = 0.66 ± 0.16 (stat) ± 0.05 (syst) and f+ = - 0.03 ± 0.06 (stat) ± 0.03 (syst). All these results are consistent with standard model expectations. © 2009 Elsevier B.V.Measurement of the top-quark mass with dilepton events selected using neuroevolution at CDF.
Phys Rev Lett 102:15 (2009) 152001