Abstract
The QED running coupling constant α(s) and the anomalous magnetic moment of muon aμare two fundamental quantities for the precision test of the Standard Model (SM). The current uncertainties on α(s) and aμare dominated by the contribution from the R-values measured about 20 years ago with an averaged uncertainty of 15% in the energy region below 5 GeV. This review article summarizes the recent measurements of R-values in low energy e+e-annihilation. The new experiments aimed at reducing the uncertainties in R-values and performed with the upgraded Beijing Spectrometer (BESII) at Beijing Electron Positron Collider (BEPC) in Beijing and with Cryogenic Magnetic Detector, CMD-2 and SND (Spherical Neutral Detector) at VEEP-2M in Novosibirsk are reviewed and discussed.
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