Measurement of the $\mathrm{t}\bar{\mathrm{t}}$ production cross section in the τ+jets channel in pp collisions at $\sqrt{s}=7\ \mbox{TeV}$

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 τ 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 τ trigger. A neural network has been developed to separate the top-quark pairs from the W+jets and multijet backgrounds. The measured value of $\sigma_{\mathrm{t}\bar{\mathrm{t}}} = 152\pm 12\,(\mbox{stat.})\pm 32\,(\mbox{syst.})\pm3\,(\mbox{lum.})\ \mbox{pb}$ is consistent with the standard model predictions.