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.

The principle of the method for the BES event start time determination and the code construction are described. The investigation of influence of the noise, the method of rejecting noise and the performance checking by the Monte Carlo physics data sample are also presented. The preliminary results got from the Monte Carlo simulation are presented, the reconstruction efficiency of J/ψ → anything events at noise level 0 ∼ 60% can achieve above 99%, and the error rate is below 1%.

Material effect of inner-detectors on the performances of the BES Electromagnetic Calorimeter (EMC) is investigated. The BES Time-Of-Flight counters (TOF) have been utilized to improve the energy resolution and detection efficiency for photons after a careful energy calibration. A matching algorithm between TOF and EMC energy deposits is developed, and the effects of beam-related background are discussed. The energy resolution is improved and the photon detection efficiency can be increased by the combined measurement of EMC and TOF detectors.

We describe the algorithm to reconstruct the charged tracks for BES main drift chamber at BEPC , including the track finding and fitting. With a new method of the Track Segment Finder (TSF), the results of present study indicate that the algorithm can reconstruct the charged tracks over a wide range of momentum with high efficiency, while improving the robustness against the background noise in the drift chamber. The overall performances, including spatial resolution, momentum resolution and secondary vertices reconstruction efficiency, etc. satisfy the requirements of BES experiment.

Particle identif ication using artif icial neural networks at BES * QIN Gang( ) 1,2;1) L Ü Jun-Guang( ) 1;2) HE Kang-Lin(ZHANG Ling( ) 5 ZHANG Xue-Yao( ) 6 ZHANG Yao( ) 6ZHU Yong-Sheng( ) 1 ZOU Jia-Heng( ) 6