High Precision Test of QCD at Beijing Electron Positron Collider

Bo-Qiang Ma

The generalized Crewther relation relates the cross section ratio $R=\sigma (e^{+}{e}^{-}\to \mathrm{hadrons})/\sigma (e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-})$ in $e^{+}{e}^{-}$ annihilation with the Bjorken sum rule or the Gr…