Direct Measurement of theπ−Form Factor

We have measured the electromagnetic form factor of the charged pion by direct scattering of 100-GeV/c ${\pi }^{-}$ from stationary electrons in a liquid-hydrogen target at Fermilab. The deviations from the pointlike pion-scattering cross section may be characterized by a root-mean-square charge radius for the pion of ${〈{{\mathcal{r}}_{\pi }}^2〉}^{\frac{1}{2}}=0.56\mathrm{}\pm 0.04$ F.