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Open Access item Observation of single top quark production and measurement of vertical bar V-tb vertical bar with CDF

Authors:Aaltonen, T.
Cabrera, Susana
Cuenca Almenar, Cristóbal
Álvarez González, B.
Casal, Bruno
Cuevas, Javier
Gómez, G.
Rodrigo, Teresa
Ruiz Jimeno, Alberto
Scodellaro, Luca
Vila, Iván
Vilar, Rocío
Issue Date:15-Dec-2010
Publisher:American Physical Society
Citation:Physical Review D 82(11): 112005 (2010)
Abstract:We report the observation of electroweak single top quark production in 3: 2 fb(-1) of p (p) over bar collision data collected by the Collider Detector at Fermilab at root s = 1.96 TeV. Candidate events in the W + jets topology with a leptonically decaying W boson are classified as signal-like by four parallel analyses based on likelihood functions, matrix elements, neural networks, and boosted decision trees. These results are combined using a super discriminant analysis based on genetically evolved neural networks in order to improve the sensitivity. This combined result is further combined with that of a search for a single top quark signal in an orthogonal sample of events with missing transverse energy plus jets and no charged lepton. We observe a signal consistent with the standard model prediction but inconsistent with the background-only model by 5.0 standard deviations, with a median expected sensitivity in excess of 5.9 standard deviations. We measure a production cross section of 2.3-(+0.6)(0.5) (stat + sys) pb, extract the value of the Cabibbo-Kobayashi-Maskawa matrix element vertical bar V-tb vertical bar = 0.91(-0.11)(+0.11) (stat + sys) +/- 0.07 (theory), and set a lower limit vertical bar V-tb vertical bar > 0.71 at the 95% C. L., assuming m(t) = 175 GeV/c(2).
Description:59 páginas, 40 figuras, 8 tablas.-- CDF Collaboration: et al.
Publisher version (URL):http://dx.doi.org/10.1103/PhysRevD.82.112005
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