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Register a new userMeasurement of the Top Quark Mass in ppbar Collisions at sqrt(s) = 1.96 TeV using the Decay Length Technique
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A. Abulencia et al.
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We report the first measurement of the top quark mass using the decay length technique in ppbar collisions at a center-of-mass energy of 1.96 TeV. This technique uses the measured flight distance of the b hadron to infer the mass of the top quark in lepton plus jets events with missing transverse energy. It relies solely on tracking and avoids the jet energy scale uncertainty that is common to all other methods used so far. We apply our novel method to a 695 pb^-1 data sample recorded by the CDF II detector at Fermilab and extract a measurement of m_t = 180.7^{+15.5}_{-13.4} (stat.) pm 8.6 (syst.) GeV/c^2. While the uncertainty of this result is larger than that of other measurements, the dominant uncertainties in the decay length technique are uncorrelated with those in other methods. This result can help reduce the overall uncertainty when combined with other existing measurements of the top quark mass.
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We report a measurement of the ttbar production cross section using dilepton events with jets and missing transverse energy in ppbar collisions at a center-of-mass energy of 1.96 TeV. Using a 197 +/- 12 pb-1 data sample recorded by the upgraded Collider Detector at Fermilab, we use two complementary techniques to select candidate events. We compare the number of observed events and selected kinematical distributions with the predictions of the Standard Model and find good agreement. The combined result of the two techniques yields a ttbar production cross section of 7.0 +2.4/-2.1(stat.) +1.6/-1.1(syst.) +/- 0.4(lum.) pb.
We report on a search for charge-1/3 third-generation leptoquarks (LQ) produced in ppbar collisions at sqrt(s)=1.96 TeV using the D0 detector at Fermilab. Third generation leptoquarks are assumed to be produced in pairs and to decay to a tau neutrino and a b quark with branching fraction B. We place upper limits on sigma(ppbar->LQLQbar)*B^2 as a function of the leptoquark mass M_{LQ}. Assuming B=1, we exclude at the 95% confidence level third-generation scalar leptoquarks with M_{LQ} < 229 GeV.
We present a search for associated Higgs boson production in the process pbar -> W/ZH -> lpmlpm + X in ee, e{mu}, and {mu}{mu} final states. The search is based on data collected by the D0 experiment at the Fermilab Tevatron Collider at sqrt{s} = 1.96 TeV corresponding to 5.3 fb-1 of integrated luminosity. We require two isolated leptons (electrons or muons) with the same electric charge and additional kinematic requirements. No significant excess above background is observed, and we set 95% C.L. observed (expected) upper limits on ratio of the production cross section to the standard model expectation of 6.4 (7.3) for a Higgs boson mass of 165 GeV and 13.5 (19.8) for a mass of 115 GeV.
We present a measurement of the inclusive jet cross section using the Run II cone algorithm and data collected by the D0 experiment in p pbar collisions at a center-of-mass energy sqrt(s)=1.96 TeV, corresponding to an integrated luminosity of 0.70 fb^(-1). The jet energy calibration and the method used to extract the inclusive jet cross section are described. We discuss the main uncertainties, which are dominated by the jet energy scale uncertainty. The results cover jet transverse momenta from 50 GeV to 600 GeV with jet rapidities in the range -2.4 to 2.4 and are compared to predictions using recent proton parton distribution functions. Studies of correlations between systematic uncertainties in transverse momentum and rapidity are presented.
We present a measurement of the charge asymmetry in top-antitop production using data corresponding to an integrated luminosity of $0.70 fb^{-1}$ of proton-proton collisions at $sqrt s = 7$ TeV collected by the ATLAS detector. The top pair events decaying semileptonically (lepton+jets channel) to either an electron or muon, missing transverse energy and at least four jets are selected. The reconstruction of the $tbar{t}$ events was performed using a kinematic likelihood approach. The difference of absolute values of top and antitop rapidities is used to define the charge asymmetry: $A_{C} = (N(|Delta Y|>0) - N(|Delta Y|<0)) / (N(|Delta Y>0) + N(|Delta Y|<0))$. To allow comparisons with theory calculations, a Bayesian unfolding technique is applied to correct the measured $|Delta Y|$ distributions for acceptance and detector effects. The top charge asymmetry in both channels (e and mu) after correction is measured to be: $A_{C} = -0.009 pm 0.023 (stat) pm 0.032 (syst)$ (e+jets channel) and $A_{C} = -0.028 pm 0.019 (stat) pm 0.022 (syst)$ ($mu$+jets channel) giving a combined result of : $A_{C} = -0.024 pm 0.016 (stat) pm 0.023 (syst)$. These results are compatible with the Standard Model predictions of $A_{C}=0.006$.
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