Elastic-Scattering Measurement of the Negative-Pion Radius

Abstract

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