Bulletin of the American Physical Society
2007 APS April Meeting
Volume 52, Number 3
Saturday–Tuesday, April 14–17, 2007; Jacksonville, Florida
Session R14: Top III |
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Sponsoring Units: DPF Chair: Jerry Blazey, Northern Illinois University Room: Hyatt Regency Jacksonville Riverfront City Terrace 10 |
Monday, April 16, 2007 10:45AM - 10:57AM |
R14.00001: Measurement of the Ratio $q\bar{q}/g\bar{g}$ in the $t\bar{t}$ Production Mechanism using the Dilepton Channel at CDF Naoki Kimura We present a measurement of the $q\bar{q}$ vs $g\bar{g}$ ratio in $t\bar{t}$ production from $p\bar{p}$ collisions at $\sqrt{s}$=1.96 TeV at the Tevatron using the CDF detector with 1.2 fb$^{-1}$ of data. According to the Standard Model, $t\bar{t}$ pairs are produced by $q\bar{q}$ annihilation 85\% of the time, and gluon-gluon fusion 15\% of the time. If the observed ratio is very different from prediction, it could be an indication of new physics. We measure the ratio using $t\bar{t}$ events decaying into the dilepton channel($t\bar{t} \rightarrow WbWb \rightarrow l\nu b l\nu b$). $q\bar{q}$ annihilation and gluon-gluon fusion have different characteristic spin configurations, and this difference manifests itself in the lepton's flight direction. Therefore we can measure this production ratio using a likelihood fit to the distribution of azimuthal angle between the leptons. [Preview Abstract] |
Monday, April 16, 2007 10:57AM - 11:09AM |
R14.00002: Measurement of the $t\bar{t}$ production cross section at D0 using $\tau$+jets events Amnon Harel We report on the measurement of the $t\bar{t}$ production cross section with candidate events in which the W boson from one of the top quarks decays into a $\tau$ lepton and the associated neutrino while the other $W$ boson decays to a quark-antiquark pair. We select events in which the $\tau$ lepton subsequently decays to one or three charged hadrons plus neutral hadrons and a neutrino. [Preview Abstract] |
Monday, April 16, 2007 11:09AM - 11:21AM |
R14.00003: Measurement of the $t\bar{t}$ production cross section at D0 using event kinematics Hwidong Yoo We report on the measurement of the $t\bar{t}$ production cross section using candidate events in the lepton+jets final state. We separate the $t\bar{t}$ signal from background processes using kinematic information. Several kinematic variables are combined into a multivariate discriminant to maximize the separation between signal and background. [Preview Abstract] |
Monday, April 16, 2007 11:21AM - 11:33AM |
R14.00004: Measurement of the $t\bar{t}$ production cross section at D0 using soft lepton $b$ tagging Michele Weber We report on the measurement of the $t\bar{t}$ production cross section using candidate events in the lepton+jets final state. We separate the $t\bar{t}$ signal from background processes by the requirement that one or more jets are identified as $b$ jets by a soft lepton tag. [Preview Abstract] |
Monday, April 16, 2007 11:33AM - 11:45AM |
R14.00005: Measurement of the $t\bar{t}$ cross section and spin correlation in the dilepton channel with the D0 detector Jens-Peter Konrath One remarkable property of top quarks is their short lifetime. Therefore the spin correlation between the top and anti-top produced in $p\bar{p}$ collisions is not degraded by hadronization. We determine the production cross section and spin correlation of $t\bar{t}$ quark pairs decaying in the dilepton mode. In this decay channel, both leptons can be used to analyze the spin correlation. Moreover, physics and instrumental background can be suppressed to a great extent. This analysis is based on data taken with the D0 Detector at the Fermilab Tevatron $p\bar{p}$-collider at a center-of-mass energy of 1.96 TeV. The data corresponding to an integrated luminosity of about 1.1 fb$^ {-1}$ were recorded in the years 2002 to 2006. [Preview Abstract] |
Monday, April 16, 2007 11:45AM - 11:57AM |
R14.00006: Measurement of the $t\bar{t}$ Production Cross Section in the Lepton+Jets Channel with Lifetime Tagging Hwidomg Yoo We present a measurement of the $t\bar{t}$ production cross section at a center-of-mass energy of 1.96 TeV. This analysis is based on the selection of events with one charged lepton (electron or muon), missing transverse energy, and 3 or more jets with $p_T > 20$ GeV and $|\eta| < 2.5 $. We utilize the e+jets (913 pb$^{-1}$) and $\mu$+jets (871 pb$^{-1} $) data samples collected using the D\O\ detector. To help distinguish the signal from the background processes, we use a Neural Network algorithm that uses lifetime information to identify the b-quark jets that are associated with top quark decays. We require at least one b- tagged jet to be identified in this analysis. [Preview Abstract] |
Monday, April 16, 2007 11:57AM - 12:09PM |
R14.00007: Measurement of $t\bar{t}$ pair production at D0 using lepton+hadronic $\tau$ events Suharyo Sumowidagdo We present the measurement of top quark-antiquark pair production in lepton+hadronic tau channel using approximately 0.9 inverse femtobarn of D0 data. We select events with one isolated high $p_{T}$ electron or muon, one isolated hadronic tau, high missing transverse energy, and two high $p_{T}$ jets. One or more of the jets are required to have originated from a b quark by applying neural network tagging algorithm. We discuss the results both within the context of Standard Model and a semi model-independent approach of non-SM production mechanism of tau lepton in top quark decay. [Preview Abstract] |
Monday, April 16, 2007 12:09PM - 12:21PM |
R14.00008: The Top Quark Width at the CDF Experiment Satomi Shiraishi We study a measurement of the total width of the top quark, thus the top quark lifetime, from $p\bar{p}$ collisions recorded at the CDF experiment in Run II of the Fermilab Tevatron. In each $t\bar{t}$ event in the lepton+jets final state, the reconstructed top quark invariant mass is determined by minimizing a $\chi^2$ for the overconstrained kinematic system, and the reconstructed mass distribution is formed for the selected event sample. The top quark width is extracted by fitting the reconstructed mass distribution to a template function which incorporates top quark events and expected backgrounds, and varies with the top quark width. [Preview Abstract] |
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