Performance study of particle identification at the CEPC using TPC dE/dx information

The kaon identification is crucial for the flavor physics, and also benefits the flavor and charge reconstruction of the jets. We explore the particle identification capability for tracks with momenta ranging from 2-20 GeV/c using the $dE/dx$ measurements in the Time Projection Chamber at the future Circular Electron-Positron Collider. Based on Monte Carlo simulation, we anticipate that an average $3.2~\sigma$ ($2.6~\sigma$) $K/\pi$ separation can be achieved based on $dE/dx$ information for an optimistic (conservative) extrapolation of the simulated performance to the final system. Time-of-flight (TOF) information from the Electromagnetic Calorimeter can provide $K/\pi$ separation around 1 GeV/c and reduce the $K/p$ mis-identification rate. By combining the $dE/dx$ and TOF information, we estimate that in the optimistic scenario a kaon selection in inclusive hadronic $Z$ decays with both the average efficiency and purity approaching 95\% can be achieved.