Direct Measurement of the Negative-Kaon Form Factor

The electromagnetic form factor of the negative kaon has been measured by direct scattering of 250-GeV/c kaons from the stationary electrons of a liquid-hydrogen target The deviation of the measured elastic scattering cross section from the point cross section may be characterized by a root-mean-square kaon radius of ${〈{{\mathcal{r}}_{K^{-}}}^2〉}^{\frac{1}{2}}=0.53\mathrm{}\pm 0.05$ fm.