Measurement of the top - antitop mass difference in pp collisions at sqrt(s) = 8 TeV

The invariance of the standard model under the CPT transformation predicts equality of particle and antiparticle masses. This prediction is tested by measuring the mass difference between the top and the antitop quark ($\Delta m_{\text{t}} = m_{\mathrm{t}} - m_{\overline{\mathrm{t}}}$), using events with a muon or an electron and at least four jets in the final state. The analysis is based on $\sqrt{s} = 8$\TeV data collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of $18.92 \pm 0.76 \fbinv$, and yields a value of $\Delta m_{\mathrm{t}} = -272 \pm 196 ~\stat \pm 122 ~\syst\MeV$ that is consistent with the standard model prediction. The accuracy of this result is significantly higher than that of existing measurements.