list of 2008 abstracts: http://www-d0.fnal.gov/Run2Physics/top/top_public_web_pages/abstracts/APS08_abstracts.pdf 2009 abstract list: ------------------- -------------------------------------------------------------------------- Using Boosted Decision Trees to Search for Single Top Quark Events at the DZero Experiment Ann Heinson, University of California, heinson@fnal.gov We present the results of a search for single top quark production at the DZero experiment at the Fermilab Tevatron proton-antiproton collider using boosted decision trees to separate signal from background. --------------------------------------------------------------------------- Using Bayesian Neural Networks to Search for Single Top Quark Events at the DZero Experiment Andres Tanasijczuk, Universidad de Buenos Aires, andres@fnal.gov (visa extension needed) We present the results of a search for single top quark production at the DZero experiment at the Fermilab Tevatron proton-antiproton collider using Bayesian neural networks to separate signal from background. --------------------------------------------------------------------------- Using Matrix Elements to Search for Single Top Quark Events at the DZero Experiment Monica Pangilinan, Brown University, mop3@fnal.gov We present the results of a search for single top quark production at the DZero experiment at the Fermilab Tevatron proton-antiproton collider using matrix elements to separate signal from background. --------------------------------------------------------------------------- Search for Anomalous Top Quark Couplings at D0 Reinhard Schwienhorst, Michigan State University, schwier@fnal.gov Anomalous Wtb couplings modify the angular correlations of the top quark decay products and change the single top quark production cross section. We present limits on anomalous top quark couplings by combining information from W boson helicity measurements in top quark decays and anomalous coupling searches in the single top quark final state. We set limits on right-handed vector couplings as well as left-handed and right-handed tensor couplings based on data collected by the D0 experiment. --------------------------------------------------------------------------- Search for Charged Higgs Bosons in Decays of Top Quarks Supriya Jain, University of Oklahoma, sjain@fnal.gov We present a search for charged Higgs bosons in the mass range $80 < m_{H^{\pm}} < 155$~GeV, assuming the decay $H^{+} \rightarrow \tau^{+} \nu_\tau$ (and its charge conjugate). Using 0.9~fb$^{-1}$ of lepton+jets data collected by the D0 detector, at the Fermilab Tevatron $p\bar{p}$ collider, we find no evidence for signal, and exclude branching ratios $B(t \rightarrow H^+b)$ at $95\%$ confidence level. --------------------------------------------------------------------------- Measurement of SM ttbar Cross Section in tau+jets Channel Diego Menezes, Northern Illinois University, dmenezes@fnal.gov The Standard Model predicts that the top quark decays almost exclusively into a $W$ boson and a $b$-quark. The final state of the top-antitop system is therefore defined by subsequent decays of the $W$ boson. We present here results of $t\bar{t}$ cross-section measurements ($\sigma_{t\bar{t}}$) using events where one of the $W$ bosons decays into a tau-lepton and the other decays hadronically: (``tau+jets'') channel. This mode is particularly challenging since the tau-leptons have a signature similar to jets in the detector, and are, therefore, difficult to identify. We report here $\sigma_{t\bar{t}}$ measurements from $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV, using data from the D0 detector. --------------------------------------------------------------------------- Measurement of the Mass Difference between Top and Antitop. Michael Wang, Universty of Rochester, mwang@fnal.gov We discuss a measurement of the mass difference ($\Delta_m$) between $t$ and $\overline{t}$ quarks in lepton+jets final states of $t\overline{t}$ events in data collected with the \dzero detector at Fermilab's Tevatron. $\Delta_m$ is measured using the Matrix-Element approach developed at \dzero [1]. We report the most likely $\Delta_m$ and an upper limit on $\Delta_m$ at 95\% confidence. This is the first measurement of a mass difference between a quark and its antiquark. --------------------------------------------------------------------------- Measurement of the ttbar Production Cross Section at D0 Using Event Kinematicsl+jets Sehwook Lee, Iowa State University, merciful@fnal.gov We report on the measurement of the ttbar production cross section based on 4 fb-1 of data using candidate events in the lepton+jets final state. We separate the signal from background processes using kinematic information. Several kinematic variables are combined into a multivariate discriminant to maximize the separation between signal and background. --------------------------------------------------------------------------- Measurement of the ttbar Production Cross Section in the Lepton+Jets Channel with Lifetime Tagging Dookee Cho , Boston University, dkcho@fnal.gov We present a measurement of the 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. We utilize the e+jets (4 fb-1) and mu+jets (4 fb-1) data samples collected using the D0 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. --------------------------------------------------------------------------- Precision Measurement of Top Quark mass in l+jets channel using ideogram method with 4 fb^-1 data at D0 Vivek Parihar, Boston University, parihar@fnal.gov We provide an update to the precision measurement of top quark mass using the ideogram technique. We select events with one charged lepton (e or mu), missing transverse energy and jets in the final state. These events are then reconstructed using a kinematic fit, which is improved upon by calculating an analytical likelihood for each event by using the statistical information and all possible jet to parton assigments. The likelihood also entails the probability that the event was a signal or background kind. The invariant mass of jets from hadronically decaying W boson in top like events is used to fit the the Jet Energy Scale in situ. --------------------------------------------------------------------------- Measurement of The Top Quark Electric Charge Jeong Ku Lim, Korea University, jklim@fnal.gov In the Standard Model, the decay of the top quark: $t \to b W^+$ gives an electric charge of $2/3$ for the top quark. However the decay $t \to bar{b}W^+$ does not violate any fondamental laws and it predicts a top quark charge of $4/3$. We provide a measurement of the electric charge of the top quark using $t \bar{t}$ events in the lepton + 4 jets final state using events 4~$fb^{-1}$ of D0 data. --------------------------------------------------------------------------- New Method For Extracting the Mass of the Top Quark From All-Jets Events Gianluca Petrillo, University of Rochester, petrillo@fnal.gov Six-jet events, arising from decays of $t\bar{t}$ pairs in which both tops decay into a $W$ boson and a $b$ quark, and both $W$s decay into quark-antiquark pairs, constitute a potentially rich source of completely reconstructable top quarks for mass extraction analyses. However, even when two of the jets are tagged as originating from b-quarks, the mass analysis is complicated by uncertainties in assigning the four other jets to their originating partons when assembling the $\bar{t}t$ pairs. We introduce and describe a new top mass extraction technique that directly addresses this complication, and present preliminary results from applying this technique to data recorded by the D0 experiment at the Fermilab Tevatron. ---------------------------------------------------------------------------