Top quark physics at CDF

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0:04 [1] and is measured at CDF to be ll = 0:04 0:56 [2] in the dilepton channel and lj = 0:72 0:69 [3] in the lepton+jets channel. The measurements are done by fitting Monte Carlo (MC) angular distribution templates to data corresponding to 5.1 fb 1 and 5.3 fb 1 of integrated luminosity, respectively. In the SM the top quark decays into a W boson and a b quark almost 100% of the time. Therefore, two b quarks are expected in each top pair event. The finite b-tagging eciency determines the size of top pair event samples with 0, 1, or 2 tagged jets. The ratio R = BR(t!Wb)/ qBR(t!Wq), where q = d, s, or b, is measured at CDF from the size of each subsample via a 2D likelihood fit to data corresponding to the full integrated luminosity of 8.7 fb 1 , simultaneosuly with the top pair production cross section (p p! t t). The results are R = 0.94 0.09 and (p p! t t) = 7.5 1.0 pb [4]. Then R is used to constrain the CKM matrix elementjVtbj to be 0.97 0.05 orjVtbj>0.89 at 95% confidence level (CL), assuming a unitary 3 3 CKM matrix [4]. Single top quarks are produced via electroweak (EW) interaction mechanisms, by the exchange of a W boson in the s or t channel. Single top production in association with a W boson is very suppressed at the Tevatron but is included for consistency in the signal model. The measurement of the single top production cross section is an important test of the SM as it is sensitive to new physics, such as flavor-changing neutral currents, heavy weak bosons W 0 and CP violation, and also provides a direct measurement of jVtbj. It is experimentally challenging because it requires the extraction of a small signal out of a large background with large uncertainty. The measurement is based on the use of neural network to discriminate