Top Quark Mass Measurements at the $$t\bar{t}$$ Threshold with CEPC

We present a study of top quark mass measurements at the $$t\bar{t}$$ t t ¯ threshold based on CEPC. A centre-of-mass energy scan near two times of the top quark mass is performed and the measurement precision of top quark mass, width and $$\alpha _S$$ α S are evaluated using the $$t\bar{t}$$ t t ¯ production rates. Realistic scan strategies at the threshold are discussed to maximise the sensitivity to the measurements individually and simultaneously in the CEPC scenarios assuming a total luminosity limited to 100 fb $$^{-1}$$ - 1 . With the optimal scan for individual property measurements, the top quark mass precision is expected to be 9 MeV, the top quark width precision is expected to be 26 MeV, and $$\alpha _S$$ α S can be measured at a precision of 0.00039, considering only the statistical uncertainty. Taking into account the systematic uncertainties from theory, width, $$\alpha _S$$ α S , experimental efficiency, background subtraction, beam energy and luminosity spectrum, the top quark mass can be measured at a precision of 25 MeV optimistically and 59 MeV conservatively at CEPC.