Total cross section for hadron production by e+e− annihilation at petra energies

The cross section for the process e+e− → multihadrons has been measured at the highest PETRA energies. We measure R (the total cross section in units of the point-like e+e- → μ+μ- cross section) to be 2.9 ± 0.7, 4.0 ± 0.5, 4.6 ± 0.4 and 4.2 ± 0.6 at s of 22, 27.7, 30 and 31.6 GeV, respectively. The observed average multiplicity, together with existing low energy data, indicate a rapid increase in multiplicity with increasing energy.