The principle of the method for the BESIII TOF calibration using cosmic ray data without magnetic field are reported in this paper. After applying calibration constants, the single-end readout time resolution could reach about 150 ps, and the time resolution for one layer is achieved to be about 110 ps. The paper also described the extraction scheme for the event start time of cosmic events.
A photon conversion finder （PCF） based on track information from the main drift chamber （MDC） of the Beijing Spectrometer （BESⅢ） at the Beijing Electron Positron Collider （BEPCⅡ） is developed. The validation of the PCF is done by reconstructing π 0 and measuring the branching fraction of J/ψ→γη . Using the developed PCF tool, we mapped the materials from the interaction point through the BEPCII beam pipe up to the inner wall of the MDC.
The time calibration for end cap TOF system of BESIII is studied in this paper. It has achieved about 110 ps time resolution for muons in dimu events. The pulse height correction using electronic scan curve and the predicted time calculated using Kalman filter method are introduced. This paper also describes the study of using electrons and muons as calibration samples.
