Measurement of the mass difference between top and anti-top quarks in pp collisions at √s = 7 TeV using the ATLAS detector

A measurement of the mass difference between top and anti-top quarks is presented. In a 4.7 fb−1 data sample of proton-proton collisions at √s = 7 TeV recorded with the ATLAS detector at the LHC, events consistent with tt¯ production and decay into a single charged lepton final state are reconstructed. For each event, the mass difference between the top and anti-top quark candidate is calculated. A two b -tag requirement is used in order to reduce the background contribution. A maximum likelihood fit to these per-event mass differences yields Δm≡mt−mt¯= 0.67 ± 0.61(stat) ± 0.41(syst) GeV, consistent with CPT invariance.