Search for single top quark production in p(p)over-bar collisions at root s=1.96 TeV in the missing transverse energy plus jets topology

We report a search for single top quarkproduction with the CDF II detector using 2.1 fb{sup -1} of integrated luminosity of pp collisions at {radical}(s)=1.96 TeV. The data selected consist of events characterized by large energy imbalance in the transverse planeand hadronic jets, and no identified electrons and muons, so the sample is enriched in W{yields}{tau}{nu} decays. In order to suppress backgrounds, additional kinematic and topological requirements are imposed through a neural network, and at least one of the jets must be identified as a b quarkjet. We measure an excess of signal-like events in agreement with the standard model prediction, but inconsistent with a model without single top quarkproduction by 2.1 standard deviations ({sigma}), with a median expected sensitivity of 1.4{sigma}. Assuming a top quarkmass of 175 GeV/c{sup 2} and ascribing the excess to single top quarkproduction, the cross section is measured to be 4.9{sub -2.2}{sup +2.5}(stat+syst) pb, consistent with measurements performed in independent data sets and with the standard model prediction.