Time of Flight Detector for Charged Particle Identification Based on Circular Electron-Positron Collider

The circular electron-positron collider (CEPC) requires a 3% precision in the measurement of dE/dx to identify long-lived charged particles. However, the measurement of dE/dx has a blind area for each of charged particles of pi /K , pi /P , and K/P, having transverse momenta of 1 GeV/c, 1.6 GeV/c, and 2 GeV/c respectively. One potential solution is to use a high-precision time-of-flight (TOF) detector with a time resolution of less than 50 ps to fill in the blind area. To address this, we propose a small particle TOF detector that uses small plastic scintillators ( 1 cm x 1 cm x 0.3 cm) silicon photomultipliers for readout. In this work, we introduce the construction of the detector and calibrate its performance by using 90Sr electron collimators and high-speed waveform acquisition electronics. Using a constant fraction timing method, we find that the time resolution of the detector is about 48 ps, satisfying the CEPC's requirements for TOF detection.