Measurement of the tt̄ production cross section in the τ+jets channel in pp collisions at √s=7\ TeV

The top-quark pair production cross section in 7 TeV center-of-mass energy proton-proton collisions is measured using data collected by the CMS detector at the LHC. The measurement uses events with one jet identified as a hadronically decaying lepton and at least four additional energetic jets, at least one of which is identified as coming from a b quark. The analyzed data sample corresponds to an integrated luminosity of 3.9 fb -1 recorded by a dedicated multijet plus hadronically decaying trigger. A neural network has been developed to separate the top-quark pairs from the W + jets and multijet backgrounds. The measured value of tt = 152 12 (stat.) 32 (syst.) 3 (lum.) pb is consistent with the standard model predictions.