Huang, GS (reprint author), CAS, Inst High Energy Phys, Beijing 100039, Peoples R China.
With an upgraded Beijing Spectrometer (BESII) at the Beijing Electron Positron Collider (BEPC), the BES collaboration finished two runs of R scan in the energy region from 2 to 5 GeV. R values for all 6+95 scanned energy points are presented, with an average undertainty of 6.6%,which represents an improvement by a factor of 2-3. These measurements make an important contribution to the precision determination of alpha(M-z(2)), the QED coupling constant evaluated at the Z pole. The results also contribute to the interpretation of muon g - 2 measurement.