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We present a direct measurement of the mass difference between t and t̄ quarks using tt̄ candidate events in the lepton+jets channel, collected with the CDFII detector at Fermilab's 1.96TeV Tevatron pp̄ Collider. We make an event by event estimate of the mass difference to construct templates for top quark pair signal events and background events. The resulting mass difference distribution of data is compared to templates of signals and background using a maximum likelihood fit. From a sample corresponding to an integrated luminosity of 5.6fb-1, we measure a mass difference, ΔMtop=Mt-Mt̄=-3.3±1.4(stat) ±1.0(syst)GeV/c2, approximately 2standard deviations away from the CPT hypothesis of zero mass difference. © 2011 American Physical Society.

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Physical Review Letters