ABSTRACTS SENT TO EPS: ====================== Measurements of the Top Quark Mass in the Lepton+Jets Channel with the D0 Detector We present measurements of the top quark mass based on data collected by the D0 experiment during Run II of the Fermilab Tevatron collider using lepton+jets final states. In the lepton+jets channel, the "Matrix-Element Method" is used where for each event a probability based on the differential cross section for production is calculated as a function of the top mass and the overall jet energy scale. The overall jet energy scale is constraint by the two jets from the hadronic W boson decay. Measurement of the top quark mass in final states with two leptons using the D0 Detector We present measurements of the top quark mass based on data collected by the D0 experiment during Run II of the Fermilab Tevatron collider. We present results in dilepton final states. In the dilepton channel, three different techniques were used: the "Matrix Weighting Method" which uses a likelihood for the observed events to occur for a range of assumed top, the "Neutrino Weighting Method" where distributions are generated from event weights obtained from comparing the calculated and reconstructed missing transverse energy and the "Matrix Element Method" where for each event, a probability based on the differential cross section for production is calculated as a function of the assumed top mass. Difference Between Top and Antitop Quarks with the D0 Detector We present a measurement of the difference between the masses of the top and antitop quarks in the lepton+jets final state. The analysis is based on the "matrix element" method. The purity of the data sample is enhanced by applying a neural-net-based b-tagging technique. The data for this measurement corresponds to 1 fb-1 of integrated luminosity acquired by the D0 experiment at the Fermilab Tevatron Collider. This represents the first direct measurement of a mass difference between a quark and its antiquark and represents a test of CPT invariance. Measurement of the Top Production Cross Section with the D0 Detector We present measurements and a combination of the top quark pair production cross section in ppbar collisions in the l+jets, ll and tau-l final states (where l is an electron or muon) at a center of mass energy of sqrt(s)=1.96 TeV in up to 4 fb^{-1} of data collected with the D0 detector. Based on predictions from higher order quantum chromodynamics, we extract a mass for the top quark from the combined ttbar cross section. Measurement of differential distributions of top quarks with the D0 detector 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 ppbar 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 II 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. Observation of Single Top Quark Production with the D0 Detector We report first observation of the electroweak production of single top quarks in ppbar collisions at sqrt(s) = 1.96 TeV based on 2.3 fb^-1 of data collected by the D0 detector at the Fermilab Tevatron Collider. Using events containing an isolated electron or muon and missing transverse energy, together with jets originating from the fragmentation of b quarks, we measure a cross section of sigma(ppbar -> tb + X, tqb + X) = 3.94 +- 0.88 pb. The probability to measure a cross section at this value or higher in the absence of signal is 2.5 x 10^-7, corresponding to a 5.0 standard deviation significance for the observation. Measurement of the Wtb Coupling and the W Boson Helicity in Top Quark Decays with the D0 Detector We present the simultaneous measurement of the ratio of branching fractions, R=B(t -> Wb)/B(t -> Wq), with q being a d, s, or b quark, and the top quark pair production cross section sigma(ttbar) in the lepton plus jets channel using data at sqrt(s)=1.96 TeV collected with the D0 detector. We extract R and sigma(ttbar) by analyzing samples of events with 0, 1 and > 2 identified b jets. We also report on a model-independent measurement of the helicity of W bosons produced in top quark decays based on a 4 fb-1 sample of ttbar events in the dilepton and lepton+jets channels. W boson helicity fractions are sensitive to the ratios of different anomalous Wtb couplings as well as single top production. We set simultaneous limits on left-handed vector and right-handed vector, and left-handed vector and right-handed tensor Wtb couplings measured using the single top selection. We combined this analysis with the W boson helicity measurement to set direct upper limits on a right-handed vector coupling as well as a left-handed tensor coupling. Search for ttbar Resonances in the Lepton+Jets Final State in ppbar Collisions at sqrt{s}=1.96TeV A search for a narrow-width heavy resonance decaying into top quark pairs (X->ttbar) in ppbar collisions at sqrt(s)=1.96TeV has been performed using data collected with the D0 detector at the Fermilab Tevatron collider. This analysis considers ttbar candidate events in the lepton+jets channel with identified b-jets and the ttbar invariant mass distribution to search for evidence of resonant production. The analyzed dataset corresponds to an integrated lumiosity of 4 fb-1. We find no evidence for a narrow resonance X decaying to ttbar. Therefore we set upper limits on sigma*B(X->ttbar) for different hypothesized resonance masses using a Bayesian approach. Within a topcolor-assisted technicolor model, the existence of a leptophobic Z' boson with mass M_Z' < 820 GeV and width Gamma_Z'=0.012 M_Z' can be excluded at 95%C.L. Search for the Standard Model Higgs boson in the ttbar H --> ttbar bbar channel We present a search for the Standard Model Higgs boson produced in association with top anti-top quark pairs. This analysis considers samples of lepton+jets events with one, two or three b-tagged jets and four, five or more jets in total collected with the D0 detector, corresponding to an integrated luminosity of 4 fb-1. Kinematical differences between ttbar and ttbar H events are exploited and limits are set on the ttbar H --> ttbar bbar production cross section. An enhanced production cross section can theoretically be achieved if a t' quark is produced via a heavy G' boson (vector color octet) instead via a Standard Model gluon. An example for such a model is analysed here leading to exclusion limits on the Higgs mass. Search for fourth generation t' quarks that decay to W+b quark We present a search for pair-production of a fourth generation t' quark with its antiparticle, followed by their decay to W b, based on 4 fb-1 of data. We set upper limits on the t' pair production cross section which can be translated into limits on the t' mass. Measurement of The Top Quark Electric Charge In the Standard Model, the decay of the top quark t --> b W^+ gives an electric charge of 2/3 for the top quark. However the decay t --> bbar W^+ does not violate any fundamental laws and it predicts a top quark charge of 4/3. We provide a measurement of the electric charge of the top quark using ttbar events in lepton+4 jets final states using 4 fb-1 of D0 data. Search for Anomalous Top Quark Couplings at D0 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. Measurement of the forward-backward charge asymmetry in top quark pair production We present the first measurement of the integrated forward-backward charge asymmetry in top-antitop quark pair (ttbar) production in proton-antiproton collisions in the lepton plus jets final state. Using a b-jet tagging algorithm and kinematic reconstruction assuming ttbar+X production and decay, collected by the D0 experiment at the Fermilab Tevatron Collider, is used to measure the asymmetry for different jet multiplicities. The result is also used to set upper limits on ttbar+X production via a Z' resonance. Search for W' bosons decaying to a top quark and a bottom quark We search for the production of a heavy W' gauge boson that decays to third generation quarks in 2.3 fb-1 of ppbar collisions at sqrt(s) = 1.96 TeV, collected with the D0 detector at the Fermilab Tevatron collider. We analyze the final-state invariant mass distribution and set upper limits on the production cross section times branching fraction. We set lower mass limits for a left-handed W' boson with SM couplings and for right-handed W' bosons decaying to both leptons and quarks and decaying only to quarks. We also set limits on the coupling of the W' boson to fermions as a function of its mass. Search for Charged Higgs Bosons in ppbar collisions at sqrt{s}=1.96 TeV We report on a search for charged Higgs bosons in the mass range 80 < m_H+ < 155 GeV in decays of top quark pairs in ppbar collisions at sqrt{s}=1.96 TeV. It has been performed using ~1 fb-1 of data collected with the D0 detector at the Fermilab Tevatron collider. The search is based on the analysis of ttbar production rates in the final states with two isolated leptons (electrons or muons) and jets, one isolated lepton (electron or muon) and jets and isolated lepton (electron or muon) and tau decaying hadronically. We find no evidence for signal. The results are interpreted within a tauonic Higgs model where the charged Higgs is assumed to decay exclusively to taunu and in a leptophobic model where the charged Higgs is assumed to decay exclusively to csbar. We set upper limits on the branching fractions B(t -> H+ b -> taubar neutrino b)) and B(t -> H+ b -> c sbar b)) for low charged-Higgs masses. We also use ratios of ttbar cross sections in different final states to set upper limits on those branching fractions. Furthermore, we describe a search for quark fusion production qq' --> H+ of the charged Higgs boson reconstructed in the tb final state for a mass range 180 < m_H+ < 300 GeV. We find no evidence for heavy charged Higgs production and set limits on the production cross-section for a variety of theoretical models. Search for the Lightest Scalar Top Quark with the D0 Detector In the Minimal Supersymmetric Standard Model (MSSM), the mixing between the chiral states of the scalar partner particles of the standard model fermions is greatest for the top quark due to its large mass. In this scenario, the light stop could be the lightest squark giving it the largest production cross section at the Tevatron. We present the most recent lightest stop quark production searches from D0 for the two body decays to bottom+chargino, charm+neutralino and the three body decay bottom+charged lepton+sneutrino via a virtual chargino. NOT SUBMITTED: Search for scalar top quark production at D0 We report results of a search for the pair production of the lightest supersymmetric partner of the top quark using 1 fb-1 of data collected by the D0 detector at a ppbar center-of-mass energy of 1.96 TeV at the Fermilab Tevatron Collider. Both scalar top quarks are assumed to decay into a b quark, a charged lepton and a scalar neutrino. The search is performed in the electron plus muon and dielectron final states. The signal topology consists of two isolated leptons, missing transverse energy, and jets. We find no evidence for this process and exclude regions of parameter space in the framework of the minimal supersymmetric standard model. Another search for pair production of the lightest supersymmetric partner of the top quark is performed in the lepton+jets channel using 0.9 fb-1 of data collected by the D0 experiment. Kinematic differences between scalar top quark pair production and the dominant top quark pair production background are used to separate the two processes. First limits from Run II of the Fermilab Tevatron Collider for the scalar top quark decaying to a chargino and a b quark are obtained for scalar top quark masses of 130-190 GeV and chargino masses of 90-150 GeV. FINAL ABSTRACTS: ================ EW04 Top mass measurement (D0) (12+3) covering abstracts: Abstract 169: Measurements of the Top Quark Mass in the Lepton+Jets Channel with the D0 Detector Abstract 170: Direct Measurement of the Mass Difference Between Top and Antitop Quarks with the D0 Detector Abstract 174: Measurement of the top quark mass in final states with two leptons using the D0 Detector Tom Ferbel Univ. of Rochester TOP-MASS MEASUREMENTS FROM DO We present three analyses of the mass of the top quark (mt) using top-antitop candidate events collected by the DO experiment during the current run of the Fermilab Tevatron Collider: (i) a 3.6 events/fb sample of data in the lepton+jets channel analyzed to extract a precision value of mt using the "Matrix-Element" method (ME), wherein each event probability is calculated from the differential production cross section as a function of mt and the overall jet energy scale, with the latter partly constrained by the two jets from W decay into q.q, (ii) first measurement of the mass difference between top and antitop quarks as a check of CPT invariance in the quark sector, also utilizing the ME method in lepton+jets channels, corresponding to a 1event/fb data sample, and (iii) measurements of mt in dilepton final states (updated to 3.6 events/fb), based on "matrix" weighting, "neutrino" weighting and the ME method, relying, respectively, on the likelihood of observing the events in data for a range of assumed mt values, distributions generated from event weights used to compare the calculated and reconstructed missing transverse energies, and event probabilities based on the leading-oder differential cross section as a function of assumed mt. EW05 Top cross section/SM properties (D0) (15+3) covering abstracts: 171: Measurement of the Top Production Cross Section with the D0 Detector 175: Measurement of differential distributions of top quarks with the D0 detector 176: Measurement of the Wtb Coupling and the W Boson Helicity in Top Quark Decays with the D0 Detector 185: Measurement of The Top Quark Electric Charge with the D0 Detector Sebastien Greder IPHC Strasbourg, France We present the measurement of the top anti-top quark pair production cross section in dilepton, lepton+jets and tau+lepton final states using up to 4 fb^-1 of data collected with the D0 detector at the Fermilab Tevatron collider. We also present the combination of these channels and extract the top quark mass comparing the measured cross section to calculations in higher order QCD. Furthermore we study properties of the top quark decay products such as helicity fractions of the W bosons. W boson helicity fractions are also sensitive to the ratios of different anomalous Wtb couplings. We set simultaneous limits on left-handed vector and right-handed vector, and left-handed vector and right-handed tensor Wtb couplings and combine this with results from a search for anomalous Wtb couplings in single top production. Ew06 "Beyond the SM searches with top (D0)" (17+3) covering abstracts: Abstract 173: Search for the SM Higgs Boson in the ttH channel with the D0 Detector Abstract 181: Search for Charged Higgs Bosons with the D0 Detector Abstract 182: Search for W' bosons decaying to a top and a bottom quark with the D0 Detector Abstract 183: Measurement of the Forward-Backward Charge Asymmetry in Top-Antitop Production with the D0 Detector Abstract 184: Search for Anomalous Top Quark Couplings with the D0 Detector Abstract 185: Measurement of The Top Quark Electric Charge with the D0 Detector Abstract 186: Search for Fourth Generation t' Quarks that Decay to W+b Quark Abstract 187: Search for ttbar Resonances in the Lepton+Jets Final State with the D0 Detector Yvonne Peters Univ. of Manchester The top quark is the heaviest elementary particle known today. It is therefore an excellent candidate to search for new physics. We present searches for physics beyond the Standard Model involving top quarks. The analysed data corresponds to up to 4 fb^-1 of integrated luminosity, collected by the D0 detector at the Femilab Tevatron collider. We present various searches for new physics in the production of single top quarks such as searches for W' bosons and charged Higgs bosons. We also discuss searches in the production of top quark pairs such as searches for new resonances, Higgs bosons produced in association with top-antitop quark pairs and present a measurement of a forward backward asymmetry. Furthermore, we present a simultaneous measurement of the ratio of branching fractions, R=B(t -> Wb)/B(t -> Wq), with q being a d, s, or b quark, and search for new particles in top quark decays, such as charged Higgs bosons. We set limits in various supersymmetric models. EW07 Observation of single top at D0 abstr. 172: Observation of Single Top Quark Production with the D0 Detector Reinhard Schwienhorst Michigan State University We report first observation of the electroweak production of single top quarks in ppbar collisions at sqrt(s) = 1.96 TeV based on 2.3 fb^-1 of data collected by the D0 detector at the Fermilab Tevatron Collider. Using events containing an isolated electron or muon and missing transverse energy, together with jets originating from the fragmentation of b quarks, we measure a cross section of sigma(ppbar -> tb + X, tqb + X) = 3.94 +- 0.88 pb. The probability to measure a cross section at this value or higher in the absence of signal is 2.5 x 10^-7, corresponding to a 5.0 standard deviation significance for the observation.