We report values of $R=\sigma (e^{+}{e}^{-}\to \mathrm{hadrons})/\sigma (e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-})$ for 85 center-of-mass energies between 2 and $5\mathrm{GeV}$ measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider.

• Received 3 February 2001

DOI:https://doi.org/10.1103/PhysRevLett.88.101802