New R Values in 2-5 Gev from the Beijing Spectrometer
The values of $R = σ(e^+e^-\to {hadrons})/σ(e^+e^-\toμ^+μ^-)$ for 85 center-of-mass energies between 2 and 5 GeV were measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider, with an average uncertainty of $\sim7%$.
hep-ex↗