14 research outputs found
Histoire académique de la maladie. Propédeutique de la pédiatrie. Manuel pédagogique et méthodique pour les étudiants des établissements d'enseignement médical supérieur des niveaux d'accréditation III-IV
Effect of exogenous cytokinins on dynamics of development and differentiation of infectious structures of the pathogen of wheat powdery mildew
Effect of intravesical mitomycin C on recurrence of newly diagnosed superficial bladder cancer: interim report from the Medical Research Council Subgroup on Superficial Bladder Cancer (Urological Cancer Working Party)
Suppression of histamine-induced relaxation of rat aorta and calcium signaling in endothelial cells by two-pore channel blocker trans-NED19 and hydrogen peroxide
Redox-dependent activation of PI3-kinase is involved in growth-factor- induced proliferation of fibroblasts
Organizations Gone Wild: The Causes, Processes, and Consequences of Organizational Misconduct
Kinematic Evidence For Top-quark Pair Production In W Plus Multijet Events In P(p)over-bar Collisions At Root-s=1.8 Tev
We present a study of W+multijet events that compares the kinematics of the observed events with expectations from direct QCD W+jet production and from production and decay of top quark pairs. The data were collected in the 1992-93 run with the Collider Detector at Fermilab (CDF) from 19.3 pb-1 of proton-antiproton collisions at s =1.8 TeV. A W+2 jet sample and a W+3 jet sample are selected with the requirement that at least the two or three jets have energy transverse with respect to the beam axis in excess of 20 GeV. The jet energy distributions for the W+2 jet sample agree well with the predictions of direct QCD W production. From the W+3 jet events, a "signal sample" with an improved ratio of tt̄ to QCD produced W events is selected by requiring each jet to be emitted centrally in the event center of mass frame. This sample contains 14 events with unusually hard jet ET distributions not well described by expectations for jets from direct QCD W production and other background processes. Using expected jet ET distributions, a relative likelihood is defined and used to determine if an event is more consistent with the decay of tt̄ pairs, with Mtop=170 GeV/c2, than with direct QCD W production. Eight of the 14 signal sample events are found to be more consistent with top-quark than direct QCD W production, while only 1.7 such top-quark-like events are expected in the absence of tt̄. The probability that the observation is due to an upward fluctuation of the number of background events is found to be 0.8%. The robustness of the result was tested by varying the cuts defining the signal sample, and the largest probability for such a fluctuation found was 1.9%. Good agreement in the jet spectra is obtained if jet production from tt̄ pair decays is included. For those events kinematically more consistent with tt̄ we find evidence for a b-quark content in their jets to the extent expected from top quark decay, and larger than expected for background processes. For events with four or more jets, the discrepancy with the predicted jet distributions from direct QCD W production, and the associated excess of b-quark content, is more pronounced. © 1995 The American Physical Societ