Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Lepton + Jets Events with Lifetime b-tagging

We present a measurement of the top quark pair ($t\bar{t}$) production cross section ($\sigma_{t\bar{t}}$) in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV using 230 pb$^{-1}$ of data collected by the D0 experiment at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), missing transverse energy, and jets in the final state. We employ lifetime-based b-jet identification techniques to further enhance the $t\bar{t}$ purity of the selected sample. For a top quark mass of 175 GeV, we measure $\sigma_{t\bar{t}}=8.6^{+1.6}_{-1.5}(stat.+syst.)\pm 0.6(lumi.)$ pb, in agreement with the standard model expectation.Comment: 7 pages, 2 figures, 3 tables Submitted to Phys.Rev.Let

The ASOS Surgical Risk Calculator: development and validation of a tool for identifying African surgical patients at risk of severe postoperative complications

Background: The African Surgical Outcomes Study (ASOS) showed that surgical patients in Africa have a mortality twice the global average. Existing risk assessment tools are not valid for use in this population because the pattern of risk for poor outcomes differs from high-income countries. The objective of this study was to derive and validate a simple, preoperative risk stratification tool to identify African surgical patients at risk for in-hospital postoperative mortality and severe complications. Methods: ASOS was a 7-day prospective cohort study of adult patients undergoing surgery in Africa. The ASOS Surgical Risk Calculator was constructed with a multivariable logistic regression model for the outcome of in-hospital mortality and severe postoperative complications. The following preoperative risk factors were entered into the model; age, sex, smoking status, ASA physical status, preoperative chronic comorbid conditions, indication for surgery, urgency, severity, and type of surgery. Results: The model was derived from 8799 patients from 168 African hospitals. The composite outcome of severe postoperative complications and death occurred in 423/8799 (4.8%) patients. The ASOS Surgical Risk Calculator includes the following risk factors: age, ASA physical status, indication for surgery, urgency, severity, and type of surgery. The model showed good discrimination with an area under the receiver operating characteristic curve of 0.805 and good calibration with c-statistic corrected for optimism of 0.784. Conclusions: This simple preoperative risk calculator could be used to identify high-risk surgical patients in African hospitals and facilitate increased postoperative surveillance. © 2018 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved.Medical Research Council of South Africa gran

Measurement of the &#923;<SUB>b</SUB><SUP>0</SUP> lifetime in the decay &#923;<SUB>b</SUB><SUP>0</SUP>&#8594;J/&#968; &#923;<SUP>0</SUP> with the D0 detector

We present measurements of the &#923;<SUB>b</SUB><SUP>0</SUP> lifetime in the exclusive decay channel &#923;<SUB>b</SUB><SUP>0</SUP>&#8594;J/&#968; &#923;<SUP>0</SUP>, with J/&#968;&#8594;&#956;<SUP>+</SUP>&#956;<SUP>-</SUP> and &#923;<SUP>0</SUP> &#8594;p<SUP>&#960;-</SUP>, the B<SUP>0</SUP> lifetime in the decay B<SUP>0</SUP>&#8594;J/&#968; K<SUB>S</SUB>0 with J/&#968;&#8594;&#956;<SUP>+</SUP>&#956;<SUP>-</SUP> and K<SUB>S</SUB><SUP>0</SUP>&#8594;&#960;<SUP>+</SUP>&#960;<SUP>-</SUP>, and the ratio of these lifetimes. The analysis is based on approximately 250 pb<SUP>-1</SUP> of data recorded with the D0 detector in pp&#8254; collisions at &#8730;s=1.96 TeV. The &#923;<SUB>b</SUB><SUP>0 </SUP>lifetime is determined to be t(&#923;<SUB>b</SUB><SUP>0</SUP>)=1.22<SUB>-0.18</SUB><SUP>+0.22</SUP> (stat)&#177;0.04(syst) ps, theB<SUP>0</SUP> lifetime t(B<SUP>0</SUP>)=1.40<SUB>-0.10</SUB> <SUP>+0.11</SUP>(stat) &#177;0.03(syst) ps, and the ratio t(&#923;<SUB>b</SUB><SUP>0</SUP>) t(B<SUP>0</SUP>)=0.87<SUB>-0.14</SUB><SUP>+0.17</SUP> (stat)&#177;0.03(syst). In contrast with previous measurements using semileptonic decays, this is the first determination of the &#923;<SUB>b</SUB><SUP>0 </SUP> lifetime based on a fully reconstructed decay channel

Measurement of the WW production cross section in pp̅ collisions at √s=1.96 TeV

We present a measurement of the W boson pair-production cross section in pp̅ collisions at a center-of-mass energy of √s=1.96 TeV. The data, collected with the Run II D0 detector at Fermilab, correspond to an integrated luminosity of 224-252 pb<SUP>-1</SUP> depending on the final state (ee, eμ, or μμ). We observe 25 candidates with a background expectation of 8.1±0.6(stat)±0.6(syst)±0.5(lum) events. The probability for an upward fluctuation of the background to produce the observed signal is 2.3x10<SUP>-7</SUP>, equivalent to 5.2 standard deviations. The measurement yields a cross section of 13.8<SUB>-3.8</SUB><SUP>+4.3</SUP>(stat)<SUB>-0.9</SUB><SUP>+1.2</SUP>(syst)±0.9(lum) pb, in agreement with predictions from the standard model

Search for supersymmetry via associated production of charginos and neutralinos in final states with three leptons

D0A search for associated production of charginos and neutralinos is performed using data recorded with the D0 detector at a ppbar center-of-mass energy of 1.96 TeV at the Fermilab Tevatron Collider. This analysis considers final states with missing transverse energy and three leptons, of which at least two are electrons or muons. No evidence for supersymmetry is found in a dataset corresponding to an integrated luminosity of 320 pb-1. Limits on the product of the production cross section and leptonic branching fraction are set. For the minimal supergravity model, a chargino lower mass limit of 117 GeV at the 95% C.L. is derived in regions of parameter space with enhanced leptonic branching fractions

Erratum : Measurement of the WW production cross section in pp‾p\overline{p} collisions at s\sqrt{s} = 1.96 TeV [Phys. Rev. Lett. 94, 151801 (2005)]

D

Search for neutral supersymmetric higgs bosons in multijet events at s=1.96TeV

We have performed a search for neutral Higgs bosons produced in association with bottom quarks in pp collisions, using 260pb-1 of data collected with the D0 detector in Run II of the Fermilab Tevatron Collider. The cross sections for these processes are enhanced in many extensions of the standard model (SM), such as in its minimal supersymmetric extension at large tanâ□¡Î. The results of our analysis agree with expectations from the SM, and we use our measurements to set upper limits on the production of neutral Higgs bosons in the mass range of 90 to 150 GeV. © 2005 The American Physical Society.Universidad de Buenos Aires, Buenos AiresLAFEX Centro Brasileiro de Pesquisas Físicas, Rio de JaneiroUniversidade do Estado do Rio de Janeiro, Rio de JaneiroInstituto de Física Teórica Universidade Estadual Paulista, São PauloUniversity of Alberta, Edmonton, ABSimon Fraser University, Burnaby, BCYork University, Toronto, ONMcGill University, Montreal, QCInstitute of High Energy Physics, BeijingUniversity of Science and Technology of China, HefeiUniversidad de los Andes, Bogotá, ColombiaCenter for Particle Physics Charles University, PragueCzech Technical University, PragueInstitute of Physics Academy of Sciences Center for Particle Physics, PragueUniversidad San Francisco de Quito, QuitoLaboratoire de Physique Corpusculaire IN2P3-CNRS Université Blaise Pascal, Clermont-FerrandLaboratoire de Physique Subatomique et de Cosmologie IN2P3-CNRS, Universite de Grenoble 1, GrenobleCPPM IN2P3-CNRS Université de la Méditerranée, MarseilleLaboratoire de l'Accélérateur Linéaire IN2P3-CNRS, OrsayLPNHE IN2P3-CNRS Universités Paris VI and VII, ParisDAPNIA/Service de Physique des Particules CEA, SaclayIReS IN2P3-CNRS Université Louis Pasteur, StrasbourgUniversité de Haute Alsace, MulhouseInstitut de Physique Nucléaire de Lyon IN2P3-CNRS Université Claude Bernard, VilleurbanneIII. Physikalisches Institut A RWTH Aachen, AachenPhysikalisches Institut Universität Bonn, BonnPhysikalisches Institut Universität Freiburg, FreiburgInstitut für Physik Universität Mainz, MainzLudwig-Maximilians-Universität München, MünchenFachbereich Physik University of Wuppertal, WuppertalPanjab University, ChandigarhDelhi University, DelhiTata Institute of Fundamental Research, MumbaiUniversity College Dublin, DublinKorea Detector Laboratory Korea University, SeoulCINVESTAV, Mexico CityFOM-Institute NIKHEF and University of Amsterdam/NIKHEF, AmsterdamRadboud University Nijmegen/NIKHEF, NijmegenJoint Institute for Nuclear Research, DubnaInstitute for Theoretical and Experimental Physics, MoscowMoscow State University, MoscowInstitute for High Energy Physics, ProtvinoPetersburg Nuclear Physics Institute, St. PetersburgLund University, LundRoyal Institute of Technology and Stockholm University, StockholmUppsala University, UppsalaLancaster University, LancasterImperial College, LondonUniversity of Manchester, ManchesterUniversity of Arizona, Tucson, AZ 85721Lawrence Berkeley National Laboratory and University of California, Berkeley, CA 94720California State University, Fresno, CA 93740University of California, Riverside, CA 92521Florida State University, Tallahassee, FL 32306Fermi National Accelerator Laboratory, Batavia, IL 60510University of Illinois at Chicago, Chicago, IL 60607Northern Illinois University, DeKalb, IL 60115Northwestern University, Evanston, IL 60208Indiana University, Bloomington, IN 47405University of Notre Dame, Notre Dame, IN 46556Iowa State University, Ames, IA 50011University of Kansas, Lawrence, KS 66045Kansas State University, Manhattan, KS 66506Louisiana Tech University, Ruston, LA 71272University of Maryland, College Park, MD 20742Boston University, Boston, MA 02215Northeastern University, Boston, MA 02115University of Michigan, Ann Arbor, MI 48109Michigan State University, East Lansing, MI 48824University of Mississippi, Mississippi 38677University of Nebraska, Lincoln, NE 68588Princeton University, Princeton, NJ 08544Columbia University, New York, NY 10027University of Rochester, Rochester, NY 14627State University of New York, Stony Brook, NY 11794Brookhaven National Laboratory, Upton, NY 11973Langston University, Langston, OK 73050University of Oklahoma, Norman, OK 73019Brown University, Providence, RI 02912University of Texas, Arlington, TX 76019Southern Methodist University, Dallas, TX 75275Rice University, Houston, TX 77005University of Virginia, Charlottesville, VA 22901University of Washington, Seattle, WA 98195University of Zurich, ZurichInstituto de Física Teórica Universidade Estadual Paulista, São Paul

Search for Wbb‾Wb\overline{b} and WHWH production in pp‾p\overline{p} collisions at s\sqrt{s} = 1.96 TeV

We present a search for W b \bar{b} production in p \bar{p} collisions at sqrt{s}=1.96 TeV in events containing one electron, an imbalance in transverse momentum, and two b-tagged jets. Using 174 pb-1 of integrated luminosity accumulated by the D0 experiment at the Fermilab Tevatron collider, and the standard-model description of such events, we set a 95% C.L. upper limit on W b \bar{b}$production of 6.6 pb for b quarks with transverse momenta p_T^b > 20 GeV and b \bar{b} separation in pseudorapidity-azimuth space Delta R_bb > 0.75. Restricting the search to optimized b \bar{b} mass intervals provides upper limits on$WH$production of 9.0$-$12.2 pb, for Higgs-boson masses of 105$-$135 GeV