First measurement of the tt[over ] differential cross section dsigma/dM_{tt[over ]} in pp[over ] collisions at sqrt[s]=1.96 TeV.
Physical review letters 102:22 (2009) 222003
Abstract:
We present a measurement of the tt[over ] differential cross section with respect to the tt[over ] invariant mass, dsigma/dM_{tt[over ]}, in pp[over ] collisions at sqrt[s]=1.96 TeV using an integrated luminosity of 2.7 fb;{-1} collected by the CDF II experiment. The tt[over ] invariant mass spectrum is sensitive to a variety of exotic particles decaying into tt[over ] pairs. The result is consistent with the standard model expectation, as modeled by PYTHIA with CTEQ5L parton distribution functions.Observation of exclusive charmonium production and gammagamma --> micro;{+}micro;{-} in pp[over] collisions at sqrt[s] = 1.96 TeV.
Physical review letters 102:24 (2009) 242001
Abstract:
In CDF we have observed the reactions p + p[over] --> p + X + p[over], with X being a centrally produced J/psi, psi(2S), or chi_{c0}, and gammagamma-->micro;{+}micro;{-} in pp[over] collisions at sqrt[s] = 1.96 TeV. The event signature requires two oppositely charged central muons, and either no other particles or one additional photon detected. Exclusive vector meson production is as expected for elastic photoproduction, gamma + p --> J/psi(psi(2S)) + p, observed here for the first time in hadron-hadron collisions. We also observe exclusive chi_{c0} --> J/psi + gamma. The cross sections dsigma/dy|_{y = 0} for J/psi, psi(2S), and chi_{c0} are 3.92 +/- 0.25(stat) +/- 0.52(syst) nb, 0.53 +/- 0.09(stat) +/- 0.10(syst) nb, and 76 +/- 10(stat) +/- 10(syst) nb, respectively, and the continuum is consistent with QED. We put an upper limit on the cross section for Odderon exchange in exclusive J/psi production.Search for exclusive Z-boson production and observation of high-mass pp[over ]-->pgammagammap[over ]-->pl;{+}l;{-}p[over ] events in pp[over ] collisions at sqrt[s]=1.96 TeV.
Physical review letters 102:22 (2009) 222002
Abstract:
This Letter presents a search for exclusive Z boson production in proton-antiproton collisions at sqrt[s]=1.96 TeV, using the CDF II detector. No exclusive Z-->l;{+}l;{-} candidates are observed and the first upper limit on the exclusive Z cross section in hadron collisions is found to be sigma_{excl}(Z)<0.96 pb at 95% confidence level. In addition, eight candidate exclusive dilepton events from the process pp[over ]-->pgammagammap[over ]-->pl;{+}l;{-}p[over ] are observed, and a measurement of the cross section for M_{ll}>40 GeV/c;{2} and |eta_{l}|<4 is found to be sigma=0.24_{-0.10};{+0.13} pb, which is consistent with the standard model prediction.Search for the decays B(s)0→e+μ- and B(s)0→e+e- in CDF run II
Physical Review Letters 102:20 (2009)
Abstract:
We report results from a search for the lepton flavor violating decays Bs0→e+μ- and B0→e+μ-, and the flavor-changing neutral-current decays Bs0→e+e- and B0→e+e-. The analysis uses data corresponding to 2fb-1 of integrated luminosity of pp̄ collisions at s=1.96TeV collected with the upgraded Collider Detector (CDF II) at the Fermilab Tevatron. The observed number of B0 and Bs0 candidates is consistent with background expectations. The resulting Bayesian upper limits on the branching ratios at 90% credibility level are B(Bs0→e+μ-)<2.0×10-7, B(B0→e+μ-)<6.4×10-8, B(Bs0→e+e-)<2.8×10-7, and B(B0→e+e-)<8.3×10-8. From the limits on B(B(s)0→e+μ-), the following lower bounds on the Pati-Salam leptoquark masses are also derived: MLQ(Bs0→e+μ-)>47.8TeV/c2, and MLQ(B0→e+μ-)>59.3TeV/c2, at 90% credibility level. © 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