Physics at BES III
Dr. Klaus Goetzen (GSI-Darmstadt)

After years of planning, construction, and much hard work by many people, the upgraded Beijing Electron Positron Collider (BEPC-II) and new Beijing Spectrometer (BES-III) have successfully been commissioned in the beginning of 2008. The double ring system BEPC-II provides symmetric electron and positron beams operating at a center-of-mass-energy region between 2.0 GeV and 4.2 GeV with a design luminosity of up to 10³³ cm^-2 s^-1. This will allow to collect large samples of J/ψ, ψ’ and D_(s) and D-bar_(s) reactions up to several billion per year. Based on these enormous datasets in the Charmonium regtion many high precision measurements will be possible during the runtime of the experiment.

Since start of data taking the experiment accumulated over 200 M of J/ψ events and more than 100 M J/ψ’ events, the latter already being the world’s largest data set on this resonance.

After an overview of the accelerator and the detector, the physics program and recent experimental results will be presented.