A measurement of the cross section of top quark pair production in proton–proton collisions recorded with the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of 7 TeV is reported. The data sample used corresponds to an integrated luminosity of 2.05 fb−1. Events with an isolated electron or muon and a τ lepton decaying hadronically are used. In addition, a large missing transverse momentum and two or more energetic jets are required. At least one of the jets must be identified as originating from a b quark. The measured cross section, σtt¯=186±13(stat)±20(syst.)±7(lumi.) pb, is in good agreement with the Standard Model prediction.
Aad, G., Abbott, B., Abdallah, J., Abdel Khalek, S., Abdelalim, A. A., Abdinov, O., … Zwalinski, L. (2012). Measurement of the top quark pair cross section with ATLAS in pp collisions at √s=7 TeV using final states with an electron or a muon and a hadronically decaying τ lepton. Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 717(1–3), 89–108. https://doi.org/10.1016/j.physletb.2012.09.032