About BESIII

BEPCII is a high luminosity, multi-bunch collider, which requires a comparable high quality detector with the modern detector technology. On the one hand, the existing BESII detector is facing severe aging problems, and its electronics and data acquisition system do not support the multi-bunch mode; on the other hand, a factor of 100 increases of statistics requires a corresponding reduction of systematic errors. Therefore a modern detector, BESIII, has to be built to meet the following requirements:

1) Very good photon energy resolution, good angle resolution for photon measurement. Crystal calorimeter, such as CsI, is one of the best choice.

2) Accurate 4-momenta measurement of low momentum charged particles. A drift chamber based on He gas is one of the best choice.

3) Good hadron identification capabilities. Both Cherenkov detector and Time-of-Flight system can meet our requirements.

4) A modern data acquisition system and the front-end electronics system based on the pipeline technique, which can accommodate multi-bunch mode.

The choice of the detector components is based on physics requirements, existing experience in the collaboration, budgetary and schedule constraints, etc. The figure below shows the schematics of the BESIII detector, which consists of the following components:

1) A He gas based drift chamber with a single wire resolution better than 130mm;

2) A CsI calorimeter with an energy resolution better than 2.5%@1 GeV;

3) A Time-of-Flight system with a time resolution better than 100 ps;

4) A super-conducting solenoid magnet with a field of 1.0 Tesla;

5) A RPC based muon chamber system.

Detector parameters of BESIII are listed in the table below in comparison with BESII.

Detector parameters of BESIII in comparison with BESII