4,539 research outputs found

    Observation of WW/WZ →ℓν+ jets at CDF

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    We present the observation of WW+WZ production in the channel with an identified lepton and two jets in 4.3 fb −1 of integrated luminosity collected by the CDF II detector in p¯p collsions at √s = 1.96TeV. The measurement uses a fit to the dijet mass to disentagle the signal from the large background. The significance of the result is found to be 5.24σ and the cross section is measured to be 18.1±3.3(stat.)±2.5(syst.) pb, in good agreement with Standard Model prediction

    Electroweak physics at the Tevatron

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    We present a review of the recent Tevatron diboson measurements in leptonic and semileptonic decay modes. The most stringent limits on anomalous triple gauge couplings are reported for each final state

    Extracting Galaxy Cluster Gas Inhomogeneity from X-ray Surface Brightness: A Statistical Approach and Application to Abell 3667

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    Our previous analysis indicates that small-scale fluctuations in the intracluster medium (ICM) from cosmological hydrodynamic simulations follow the lognormal distribution. In order to test the lognormal nature of the ICM directly against X-ray observations of galaxy clusters, we develop a method of extracting statistical information about the three-dimensional properties of the fluctuations from the two-dimensional X-ray surface brightness. We first create a set of synthetic clusters with lognormal fluctuations. Performing mock observations of these synthetic clusters, we find that the resulting X-ray surface brightness fluctuations also follow the lognormal distribution fairly well. Systematic analysis of the synthetic clusters provides an empirical relation between the density fluctuations and the X-ray surface brightness. We analyze \chandra observations of the galaxy cluster Abell 3667, and find that its X-ray surface brightness fluctuations follow the lognormal distribution. While the lognormal model was originally motivated by cosmological hydrodynamic simulations, this is the first observational confirmation of the lognormal signature in a real cluster. Finally we check the synthetic cluster results against clusters from cosmological hydrodynamic simulations. As a result of the complex structure exhibited by simulated clusters, the empirical relation shows large scatter. Nevertheless we are able to reproduce the true value of the fluctuation amplitude of simulated clusters within a factor of two from their X-ray surface brightness alone. Our current methodology combined with existing observational data is useful in describing and inferring the statistical properties of the three dimensional inhomogeneity in galaxy clusters.Comment: 34 pages, 17 figures, accepted for publication in Ap