Top quark mass measurements at the t (t)over-bar threshold with CEPC

Abstract

We present a study of top quark mass measurements at the t (t) over bar 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) are evaluated using the t (t) over bar 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). 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) 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), 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.