Search for exclusive gammagamma production in Hadron-Hadron collisions.
Phys Rev Lett 99:24 (2007) 242002
Abstract:
We have searched for exclusive gammagamma production in proton-antiproton collisions at sqrt[s]=1.96 TeV, using 532 pb(-1) of integrated luminosity taken by the run II Collider Detector at Fermilab. The event signature requires two electromagnetic showers, each with transverse energy E(T)>5 GeV and pseudorapidity |eta|<1.0, with no other particles detected in the event. Three candidate events are observed. We discuss the consistency of the three events with gammagamma, pi(0)pi(0), or eta eta production. The probability that other processes fluctuate to >or=3 events is 1.7x10(-4). An upper limit on the cross section of pp-->p + gammagamma + p production is set at 410 fb with 95% confidence level.Search for exclusive γγ production in hadron-hadron collisions
Physical Review Letters 99:24 (2007)
Abstract:
We have searched for exclusive γγ production in proton-antiproton collisions at s=1.96TeV, using 532pb-1 of integrated luminosity taken by the run II Collider Detector at Fermilab. The event signature requires two electromagnetic showers, each with transverse energy ET>5GeV and pseudorapidity |η|<1.0, with no other particles detected in the event. Three candidate events are observed. We discuss the consistency of the three events with γγ, π0π0, or ηη production. The probability that other processes fluctuate to 3 events is 1.7×10-4. An upper limit on the cross section of pp̄→p+γγ+p̄ production is set at 410 fb with 95% confidence level. © 2007 The American Physical Society.Measurements of inclusive W and Z cross sections in pp̄ collisions at √s = 1.96 TeV
Journal of Physics G: Nuclear and Particle Physics 34:12 (2007) 2457-2544
Abstract:
We report the first measurements of inclusive W and Z boson cross-sections times the corresponding leptonic branching ratios for collisions at TeV based on the decays of the W and Z bosons into electrons and muons. The data were recorded with the CDF II detector at the Fermilab Tevatron and correspond to an integrated luminosity of 72.0 ± 4.3 pb-1. We test e-μ lepton universality in W decays by measuring the ratio of the W → μν to W → eν cross sections and determine a value of 0.991 ± 0.004(stat.) ± 0.011(syst.) for the ratio of W - ℓ - ν couplings (gμ/ge). Since there is no sign of non-universality, we combine our cross-section measurements in the different lepton decay modes and obtain σw × Br (pp̄ → W → ℓv) = 2.749 ± 0.010(stat.) ± 0.053(syst.) ± 0.165 (lum.) nb and σγ* × Br (pp̄ → γ*/Z → ℓℓ) = 254.9 ± 3.3(stat.) ± 4.6(syst.) ± 15.2(lum.) pb for dilepton pairs in the mass range between 66 GeV/c2 and 116 GeV/c2. We compute the ratio R of the W → ℓν to Z → ℓℓ cross sections taking all correlations among channels into account and obtain R = 10.84 ± 0.15(stat.) ± 0.14(syst.) including a correction for the virtual photon exchange component in our measured γ*/Z → ℓℓ cross section. Based on the measured value of R, we extract values for the W leptonic branching ratio, Br(W → ℓν)= 0.1082 ± 0.0022; the total width of the W boson, Γ(W)= 2092 ± 42 MeV; and the ratio of W and Z boson total widths, Γ(W)/Γ(Z)= 0.838 ± 0.017. In addition, we use our extracted value of Γ(W) whose value depends on various electroweak parameters and certain CKM matrix elements to constrain the Vcs CKM matrix element, |Vcs| = 0.976 ± 0.030. © 2007 IOP Publishing Ltd.Precise measurement of the W boson mass
Frascati Physics Series 44:SPEC. ISS. (2007) 231-242
Abstract:
The first measurement of the W boson mass (mW) hi Run 11 of the Tevatron Collider has been made by the CDF Collaboration, and is the single most precise mW measurement to date. The measurement of mW = 80.413 ± 0.048 GeV lias a relative precision of 0.06% and results in a new world-average mW of 80.398 ± 0.025 GeV. The precise knowledge of mW constrains the properties of new hypothetical particles coupling to electroweak gauge bosons.Observation of the Heavy Baryons Sigma b and Sigma b*.
Phys Rev Lett 99:20 (2007) 202001