Measurement of the mass difference between $t$ and $\bar{t}$ quarks

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We present a direct measurement of the mass difference between $t$ and $\bar{t}$ quarks using $\ttbar$ candidate events in the lepton+jets channel, collected with the CDF II detector at Fermilab's 1.96 TeV Tevatron \ppbar 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 \invfb{5.6}, we measure a mass difference, $\dmt = \mathrm{M}_{t} - \mathrm{M}_{\bar{t}} = -3.3 \pm 1.4(stat) \pm 1.0(syst)}$, approximately two standard deviations away from the CPT hypothesis of zero mass difference.