Hadron Production by Electron-Positron Annihilation at 4-GeV Center-of-Mass Energy

We have measured the total cross section for electron-positron annihilation into three or more hadrons, with at least two charged particles in the final state. The measurement was made at a center-of-mass energy of 4 GeV with a $2\pi -\mathrm{s}\mathrm{r}$ nonmagnetic detector. With 88 events detected, we obtain a model-independent lower limit on the hadron production cross section of 9.6 ± 1.4 nb; a calculation of detection efficiency based on invariant phase-space production of pions leads to a total cross section of 26 ± 6 nb. This cross section is 4.7 ± 1.1 times the theoretical total cross section for $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}$. The average charged multiplicity is $\overline{n}=4.2\mathrm{}\pm 0.6$.