6,361 research outputs found

    Forward-backward asymmetry in t¯t production

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    We present new measurements of the forward-backward asymmetry in t¯t production, performed with 5 fb−1 of Tevatron p¯p collisions at center of mass energy 1.96 TeV, recorded and analyzed at CDF. Significant inclusive asymmetries are observed in both the lepton+jets and the dilepton decay modes of the t¯t pair. In the dilepton mode, the asymmetry is observed in the reconstructed top rapidity, and in the lepton rapidity difference which is independent of any top reconstruction. In the lepton plus jets sample, the full reconstruction of the top kinematics is used to measure the dependence of the asymmetry on the rapidity difference Δy and the invariant mass Mt¯t of the t¯t system, and the asymmetry is found to be most significant at large rapidity and mass

    Asymmetries in top quark pair production at hadron colliders

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    We review the asymmetries in top quark pair production at the Tevatron and the LHC. We summarize the experimental measurements and the interpretations of a possible excess in terms of new physics. We also review other top quark properties-emphasizing effects related to the ttˉt \bar t asymmetries-as well as other collider signals.Comment: RevTeX 40 pages. Final version to be published in Reviews of Modern Physics, with several addition

    First ADS analysis of B- -> D0K- decays in hadron collisions

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    Proceedings of DISCRETE 2010, Symposium on Prospects in the Physics of Discrete Symmetries, Rome (IT), 6-11 December 2010Comment: 7 pages, 5 figure

    Characterization of the background spectrum in DAMIC at SNOLAB

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    We construct the first comprehensive radioactive background model for a dark matter search with charge-coupled devices (CCDs). We leverage the well-characterized depth and energy resolution of the DAMIC at SNOLAB detector and a detailed geant4-based particle-transport simulation to model both bulk and surface backgrounds from natural radioactivity down to 50  eVee. We fit to the energy and depth distributions of the observed ionization events to differentiate and constrain possible background sources, for example, bulk 3H from silicon cosmogenic activation and surface 210Pb from radon plate-out. We observe the bulk background rate of the DAMIC at SNOLAB CCDs to be as low as 3.1±0.6  counts kg−1 day−1 keV−1ee, making it the most sensitive silicon dark matter detector. Finally, we discuss the properties of a statistically significant excess of events over the background model with energies below 200  eVee

    Measurement of the charge asymmetry of electrons from the decays of W bosons produced in p p ¯ collisions at s =1.96 TeV

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    Publisher Copyright: © 2021 authors. Published by the American Physical Society.At the Fermilab Tevatron proton-antiproton (pp¯) collider, high-mass electron-neutrino (eν) pairs are produced predominantly in the process pp¯→W(→eν)+X. The asymmetry of the electron and positron yield as a function of their pseudorapidity constrain the slope of the ratio of the u- to d-quark parton distributions versus the fraction of the proton momentum carried by the quarks. This paper reports on the measurement of the electron-charge asymmetry using the full data set recorded by the Collider Detector at Fermilab in 2001-2011 and corresponding to 9.1 fb-1 of integrated luminosity. The measurement significantly improves the precision of the Tevatron constraints on the parton-distribution functions of the proton. Numerical tables of the measurement are provided.Peer reviewe

    Single Top Quark Production as a Probe for Anomalous Moments at Hadron Colliders

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    Single production of top quarks at hadron colliders via gWgW fusion is examined as a probe of possible anomalous chromomagnetic and/or chromoelectric moment type couplings between the top and gluons. We find that this channel is far less sensitive to the existence of anomalous couplings of this kind than is the usual production of top pairs by gggg or qqˉq\bar q fusion. This result is found to hold at both the Tevatron as well as the LHC although somewhat greater sensitivity for anomalous couplings in this channel is found at the higher energy machine.Comment: New discussion and 10 new figures added. uuencoded postscript fil