Improvement Of Partical Identification And Position Reconstruction For BESⅢ EMC

The Electromagnetic Calorimeter (EMC) is one of the important components of the BESIII detector for measuring electrons and photons with a high detection efficiency, good energy and position resolution. Precise measurement of shower position has an important effect on the reconstruction ofπ0 andη. Different informations in EMC could be used to do the particle identification. The studying and improvement in this thesis are based on the original reconstruction software, including improvement of EMC particle identification based on neural network and position reconstruction, and the studying of different position reconstruction methods and position correction.Particle identification has a significant effect on the BESIII physics analysis. For certain hardware and software systems, performance of particle identification depends on particle identification algorithms and discriminative variables. The EMC provides energy and other information for electron and pion identifications. EMC particle identification algorithm software has been improved by adding three discriminative variables and using kalP instead of MDC recP in this thesis.Precise measurement of position for electrons and photons is the primary functions of EMC. Due to interactions with matter and bias from position reconstruction algorithm, pho-tons or electrons may not be reconstructed in the proper directions. For the high position resolution, position reconstruction algorithm and correction parameters should be studied to correct EMC reconstruction positions to the expected positions. Position reconstruction software had been used for real data, but requiring further improvement. For EMC barrel, simple correction parameters had been set using Monte Carlo samples and applied to real data, but not for EMC endcaps due to complex geometry. While studying of four different position reconstruction methods, the logarithm method with front-face crystal location has been chosen as the default reconstruction method. The default reconstruction method has been used for the position correction of the barrel and endcaps in EMC, and position cor-rection parameters dependence on the shower energy and position has been considered. The performance of position reconstruction has been improved at last.