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[en] We present an effective-field-theory calculation of the effect of a dimension-six operator involving the top quark on precision electroweak data via a top-quark loop. We demonstrate the renormalizability, in the modern sense, of the effective field theory. We use the oblique parameter U-hat to bound the coefficient of the operator, and compare with the bound derived from top-quark decay.
[en] We present all order results for the heavy top corrections to the ρ parameter in the complex mass scheme. We derive translation formulas between the complex mass and the on-shell scheme and show that they are ultimately equivalent. We show that a naive treatment with a fixed width for the top quark cannot give even approximately correct results.
[en] We present an alternative approach for calculating helicity amplitudes for processes involving both massless and massive fermions. With this method one can easily obtain covariant expressions for the helicity amplitudes. The final expressions involve only four-vector products and are independent of the basis for γ matrices or specific form of the spinors. We use the method to obtain the helicity amplitudes for several processes involving top quark production. copyright 1996 The American Physical Society
[en] This paper summarizes a talk given at the Top2008 Workshop at La Biodola, Isola d'Elba, Italy. The status of the world average top-quark mass is discussed. Some comments about the challenges facing the experiments in order to further improve the precision are offered.
[en] This paper summarizes a talk given at the Top2008 Workshop at La Biodola, Isola d Elba, Italy. The status of the world average top-quark mass is discussed. Some comments about the challanges facing the experiments in order to further improve the precision are offered.
[en] Neural networks (NNs) provide a powerful and flexible tool for selecting a signal from a larger background. The D0 collaboration has used them extensively in studying t anti t decays. NNs were essential to the measurement of the t anti t production cross section in the all-jets channel (t anti t → b anti bqqqq), and were also used in the measurement of the mass of the top quark in the lepton+jets channel (t anti t → b anti blνq anti q). This paper will describe two new applications of neural networks to top quark analysis: the search for single top quark production, and an effort to increase the sensitivity in the dilepton channel t anti t → b anti be anti μν anti ν beyond that achieved in the published analysis
[en] We discuss the study of the top quark at future experiments and machines. Top's large mass makes it a unique probe of physics at the natural electroweak scale. We emphasize measurements of the top quark's mass, width, and couplings, as well as searches for rare or nonstandard decays, and discuss the complementary roles played by hadron and lepton colliders
[en] A major goal of high energy physicists over the next few years is to reduce the uncertainty in our knowledge of the top quark mass. Neural network based methods may play a useful role in this regard, as is borne out by the preliminary results reported here