Measurement of the top-quark mass from the b jet energy spectrum

The top-quark mass is measured using the peak position of the energy distribution of b jets produced from top-quark decays. The analysis is based on a recent theoretical proposal. The measurement is carried out selecting $\mathrm{t\overline{t}}$ events with one electron and one muon in the final state in proton-proton collision data at $\sqrt{s}=8~\mathrm{TeV}$, corresponding to an integrated luminosity of 19.7$~\mathrm{fb}^{-1}$. The fitted peak position of the observed energy distribution is calibrated using simulated events and translated to a top-quark mass measurement using relativistic kinematics, with the result $m_{\mathrm{t}}=172.29\pm1.17\,(\mathrm{stat.})\pm2.66\,(\mathrm{syst.})~\mathrm{GeV}$.