Research BESⅢ TOF (TOF) Aging And Improved Scale Algorithm

The upgraded BEPCⅡ/BESⅢ is a unique and powerful facility for studying in τ-Charm energy region. It will also play an important role towards our understanding of the Standard Model and enable search for possible new interactions. Time of Flight (TOF) counters as one of its sub detector is mainly used to measure the time of flight of charged particles for particle identification(PID). It is made of barrel and endcap. The barrel TOF is designed to use two layers of plastic scintillator bar directly coupled with FM-PMT. The endcap TOF will use the fan-shaped scintillators instrumented with PMTs at inner radius.This thesis focuses on the ageing which includes attenuation length and light yield of barrel TOF. In addition, this thesis also discuss the improvement of calibration algorithm.BESIII has taken data from2009and plan to work8-10years. The study of TOF ageing and it’s effect to detector is very important and necessary. This thesis study the change of attenuation and light yield versus time of every counter which sampled Bhabha events of2009.6to2012.2. We found that the average decay rate of attenuation is4.3%every year, so the TOF efficiency is strongly dependent on attenuation. This conclusion is affirmed by the psip of2012. In addition we calculate that the average decay rate of light yield is0.49%with pulse amplitude measured by TOF and information of election got by the laser calibration.The ability of particle identification of TOF is decided by the fly time difference of same momentum particles and the sigma of TOF. Considered the geometry structure is confirmed, the sigma is a main factor influencing particle identification. While analysing offline data, we found that the difference between measured time and expected time is not same to three collision belonged to one trigger cycle. Some improvement is added into calibration algorithm and the time difference approach0. Bhabha, dimu and pion sampled were check and the conclusion can be make that the sigma is improved about10%.At last, this thesis introduce the TOFODQM(TOF offline data quality monitor package). This package is aimed to improve the efficiency of checking data. The ageing of TOF is very important to maintenance of detector and set operating condition. At the same time it is a reference to the design of similar device. The improvement of TOF calibration algorithm fully excavate the potentiality of hardware and election. The sigma is enhanced. it improve the ability of particle identification which is very important to physical analysis.