Bulletin of the American Physical Society
2008 APS April Meeting and HEDP/HEDLA Meeting
Volume 53, Number 5
Friday–Tuesday, April 11–15, 2008; St. Louis, Missouri
Session J12: Top I |
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Sponsoring Units: DPF Chair: Graham Wilson, University of Kansas Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), St. Louis C |
Sunday, April 13, 2008 10:45AM - 10:57AM |
J12.00001: Measurement of the Top Quark Mass at D0 Using the Matrix-Element Method in the Dilepton Channel Alexander Grohsjean We report on the measurement of the top quark mass using candidates in the dilepton final state. For each event, a probability based on the differential cross section for production is calculated as a function of the top mass. The top mass is extracted by maximizing a likelihood constructed as the product of the single event probabilities. The measurement is based on 1 fb$^{-1}$ of data. [Preview Abstract] |
Sunday, April 13, 2008 10:57AM - 11:09AM |
J12.00002: Measurement of the ttbar Cross Section in the Dilepton Channel with the D0 Detector Marion Arthaud We present the ttbar production cross measurement using dilepton events. This analysis is based on data taken with the D0 detector at the Fermilab Tevatron 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] |
Sunday, April 13, 2008 11:09AM - 11:21AM |
J12.00003: Top quark mass measurement in the dilepton channel at CDF using a neural network event selection and matrix element method Ravi Shekhar We present a measurement of the top quark mass using events in the dilepton decay channel. The events used in this analysis are selected using a genetically-evolved artificial neural network that is optimized directly for precision in the top quark mass measurements. This is the first application of this method in high energy physics. We extract the top quark mass from a probability that a given event is consistent with $t\bar{t}$ decay in the dilepton channel. The probability is evaluated using the differential cross-section for ttbar production and decay. The effect of background events in the sample is accounted for by evaluating differential cross sections for major background processes. Using 2 $fb^{-1}$ of $p\bar{p}$ data collected at the CDF II detector, we measure $m_{t} = 171.2 \pm 2.7(\textrm{stat.}) \pm 2.9(\textrm{syst.}) \mathrm{~GeV}/c^2$. We discuss the gain in sensitivity due to the use of the evolving neural network. [Preview Abstract] |
Sunday, April 13, 2008 11:21AM - 11:33AM |
J12.00004: Study of differential distributions of top quarks Jiri Kvita The study of kinematics of top quark pairs produced at Fermilab Tevatron Collider can test Standard Model production and decay of the system or look for new physics. Differential distributions can validate current generators and their level of description of the top quark pairs and provide a detailed window on QCD dynamics of a unique heavy diquark system at large scales. We present measurements of differential distributions of top quarks produced in pairs in $p\bar{p}$ collisions recorded by the DZero experiment. Events containing a high-$p_T$ lepton, large missing transverse energy, and four or more jets were chosen from the $0.9$~fb$^{-1}$ Run~IIa data sample. At least one of the jets was required to be identified as a $b$ jet. A constrained kinematic fit associated these decay products with the individual top quarks. The measured spectra, binned in several observables, are compared to those obtained from the Monte Carlo simulation. We focus on the transverse momentum of the top quark and the top pair system as well as the system invariant mass and the azimuthal decorrelation between top quarks. [Preview Abstract] |
Sunday, April 13, 2008 11:33AM - 11:45AM |
J12.00005: Simultaneous measurement of the ratio $ {\cal {B}}( t\rightarrow Wb )/{\cal{B}}(t\rightarrow Wq )$ and the top quark pair production cross section with the D0 detector at $ \sqrt{s}=1.96$~TeV Suharyo Sumowidagdo We present the first simultaneous measurement of the ratio of branching fractions, $R={\cal{B}}(t \rightarrow Wb)/{\cal{B}}(t \rightarrow Wq)$, with $q$ being a $d$, $s$, or $b$ quark, and the top quark pair production cross section $\sigma_{t\bar{t}}$ in the lepton plus jets channel using $0.9~\mathrm{fb}^{-1}$ of $p\bar{p}$ collision data at $\sqrt{s}=1.96$~TeV collected with the D0 detector. We extract $R$ and $\sigma_{t\bar{t}}$ by analyzing samples of events with 0, 1 and $\ge 2$ identified $b$ jets. [Preview Abstract] |
Sunday, April 13, 2008 11:45AM - 11:57AM |
J12.00006: Measurement of the ttbar Cross Section in the Lepton+track Channel with the D0 Detector Robert Wagner The production cross-section for top-antitop quark pairs from proton-antiproton collisions at $\sqrt{s}=$~1.96 TeV was measured in the dilepton channel. The top quark decays almost exclusively to a Wb final state, and in the dilepton channel both of the W bosons from the top-antitop pair decay into either an electron or muon, possibly through an intermediary tau. The measurement was made using a lepton+track selection method, which selects events where only one lepton was fully identified by the detector and the second lepton is identified by an isolated track in the tracking system. The lepton+track selection is added to the fully identified channels to increase the sensitivity of the combined dilepton channel measurement. This work was performed at the D0 detector at the Tevatron collider, using about 1 fb$^{-1}$ of integrated luminosity. [Preview Abstract] |
Sunday, April 13, 2008 11:57AM - 12:09PM |
J12.00007: Meaurement of the top quark mass in the lepton+track sample at CDF Marco Trovato We report on a measurement of the top quark mass in the lepton+track sample of $t\bar t$ events at CDF. This new selection was applied to $t\bar t$ candidates in the dilepton channel in order to increase the acceptance by relaxing the cuts on one lepton. To constrain the event kinematics the azimuthal angles of the two neutrinos are assumed as known and the top quark mass is reconstructed accordingly. The full neutrino phase space is scanned and $\chi^2$-dependent weights are given to the solutions in order to build a preferred mass for each event. The integrated luminosity of the data sample is 2.1 fb$^{-1}$. 236 candidate events were reconstructed and fitted as a superposition of signal and background. In a constrained fit with 105.8 $\pm$ 12.9 background events as determined in the production cross section studies we measure $m_t$ = 167.7 + 4.2 - 4.0 (stat) $\pm$ 3.1 (syst.) GeV/c$^2$. If the background is left unconstrained we measure $m_t$ = 167.7 + 4.5 - 4.3 (stat) $\pm$ 3.1 (syst.) GeV/$c^2$. [Preview Abstract] |
Sunday, April 13, 2008 12:09PM - 12:21PM |
J12.00008: Measurement of the ttbar Production Cross Section at D0 Using Lepton + Hadronic tau Events Florent Lacroix We present the measurement of top quark-antiquark pair production in the lepton+hadronic tau channel using approximately 0.9 fb$^{-1}$ of D0 data. We select events with one isolated high pT electron or muon, one isolated hadronic tau, high missing transverse energy, and two high pT jets. One or more of the jets are required to have originated from a b quark by applying a neural network tagging algorithm. We discuss the results both within the context of the Standard Model and a semi model-independent approach of a non-SM production mechanism of a tau lepton in top quark decay. [Preview Abstract] |
Sunday, April 13, 2008 12:21PM - 12:33PM |
J12.00009: Measurement of the ttbar Production Cross Section at D0 Using tau+Jets Events Mikhail Arov We report on the measurement of the ttbar 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. The measurement is based on 1 fb$^{-1}$ of data. The signal was discriminated from background using kinematic information and by requiring an identfied b jet. [Preview Abstract] |
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