Measurement of the mass difference between top and antitop quarks

A measurement of the mass difference between the top quark and the antitop quark ($\Delta m_t = m_t - m_{\bar{t}}$) is performed using events with a muon and at least four jets in the final state. Data collected in 2011 with the CMS detector at the LHC and corresponding to an integrated luminosity of 1.09 fb$^{-1}$ are analyzed. The measured value of $\Delta m_t = -1.2 \pm 1.2 ~(\text{stat.}) \pm 0.5 ~(\text{syst.}) ~ \text{GeV}$ is consistent with the standard model.