Search for single top quark production in pbar p collisions at sqrt{s}=1.96 TeV in the missing transverse energy plus jets topology

摘要

We report a search for single top quark production with the CDF II detectorusing 2.1 fb-1 of integrated luminosity of pbar p collisions at sqrt{s}=1.96TeV. The data selected consist of events characterized by large energyimbalance in the transverse plane and hadronic jets, and no identifiedelectrons and muons, so the sample is enriched in W -> tau nu decays. In orderto suppress backgrounds, additional kinematic and topological requirements areimposed through a neural network, and at least one of the jets must beidentified as a b-quark jet. We measure an excess of signal-like events inagreement with the standard model prediction, but inconsistent with a modelwithout single top quark production by 2.1 standard deviations (sigma), with amedian expected sensitivity of 1.4 sigma. Assuming a top quark mass of 175GeV/c2 and ascribing the excess to single top quark production, the crosssection is measured to be 4.9+2.5-2.2(stat+syst)pb, consistent withmeasurements performed in independent datasets and with the standard modelprediction.