First Searches for Single Top Quark Production with ATLAS

Searches for single top-quark production in the t- and Wt-channels in 7 TeV proton-proton collisions have been carried out with the ATLAS detector using an integrated luminosity of 35 pb−1 collected in the 2010 LHC run. The t-channel search is based on the selection of events with a single lepton (muon or electron), jets and missing transverse energy. A production cross-section of sigmat = 53+46−36 pb is obtained by applying a cut-based selection, which translates to an upper limit of 162 pb at 95% confidence level. A likelihood function approach is also used to cross-check the result. Both results are consistent with the Standard Model expectation of 66 pb. The Wt-channel analysis is based on the selection of events with one or two leptons, jets and missing transverse energy. The expected Standard Model cross-section for this single-top process is 15 pb. A 95% confidence level limit is set on the Wt-channel production cross section of sigmaWt < 158 pb.