Measurement of the mass difference between top and antitop quarks

We present a measurement of the mass difference between top (t) and antitop (t ̄) quarks using tt ̄ candidate events reconstructed in the final state with one lepton and multiple jets. We use the full data set of Tevatron √s=1.96 TeV proton-antiproton collisions recorded by the CDF II detector, corresponding to an integrated luminosity of 8.7 fb−1. We estimate event by event the mass difference to construct templates for top pair signal events and background events. The resulting mass difference distribution in data compared to signal and background templates using a likelihood fit yields ΔMtop=Mt−Mt ̄=−1.95±1.11(stat)±0.59(syst) GeV/c2 and is in agreement with the standard model prediction of no mass difference.