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Observation of single top quark production and measurement of |Vtb| with CDF

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Title: Observation of single top quark production and measurement of |Vtb| with CDF
Author: Aaltonen, Timo; Mehtälä, Petteri; Orava, Risto; Saarikko, Heimo; Österberg, Kenneth; CDF Collaboration
Citation: Aaltonen , T , Mehtälä , P , Orava , R , Saarikko , H , Österberg , K & CDF Collaboration 2010 , ' Observation of single top quark production and measurement of |Vtb| with CDF ' , Physical Review D : Particles, Fields, Gravitation and Cosmology , vol 82 , no. 11 , pp. 112005 .
Belongs to series: Physical Review D : Particles, Fields, Gravitation and Cosmology
ISSN: 1550-7998
Abstract: We report the observation of electroweak single top quark production in 3.2  fb-1 of pp̅ collision data collected by the Collider Detector at Fermilab at √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 2.3-0.5+0.6(stat+sys)  pb, extract the value of the Cabibbo-Kobayashi-Maskawa matrix element |Vtb|=0.91-0.11+0.11(stat+sys)±0.07  (theory), and set a lower limit |Vtb|>0.71 at the 95% C.L., assuming mt=175  GeV/c2.
Peer review status: Peer reviewed
URI: http://hdl.handle.net/10138/24162
Date: 2010-12-15

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