Elastic-Scattering Measurement of the Negative-Pion Radius

A new measurement of the elastic scattering of 250-GeV/c negative pions by electrons provides form-factor results from $0.0368<\mathrm{}{q}^2<0.0940\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. These measurements determine the mean square pion radius to be $〈{r_{\pi }}^2〉=0.439\mathrm{}\pm 0.030$ ${\mathrm{fm}}^2$ or ${〈{r_{\pi }}^2〉}^{\frac{1}{2}}=0.663\mathrm{}\pm 0.023$ fm. Comparisons are made with previous elastic-scattering experiments as well as with results obtained from electroproduction experiments, $e^{+}{e}^{-}$ annihilation experiments, and phenomenological analyses.