Measurement of the top quark pair cross section with ATLAS in pp collisions at sqrt(s) = 7 TeV using final states with an electron or a muon and a hadronically decaying tau lepton

TL;DR

This paper reports a measurement of the top quark pair production cross section at 7 TeV using ATLAS data, focusing on final states with an electron or muon, a hadronically decaying tau, jets, and missing transverse momentum, confirming Standard Model predictions.

Contribution

It presents the first measurement of the top pair production cross section in final states with a tau lepton at 7 TeV with ATLAS, using a novel event selection and analysis method.

Findings

Measured cross section: 186 pb with uncertainties

Results agree with Standard Model predictions

Demonstrates feasibility of tau-inclusive top quark measurements

Abstract

A measurement of the cross section of top quark pair production in proton-proton collisions recorded with the ATLAS detector at the LHC 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 tau 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, sigma_ttbar = 186+/- 13 (stat) +/- 20 (syst) +/- 7 (lum.) pb is in good agreement with the Standard Model prediction.