Backward-Angle Electron-Proton Elastic Scattering and Proton Electromagnetic Form Factors

Elastic electron-proton scattering cross sections were measured at backward angles (80°-90°) in the laboratory for four-momentum transfers between 7 ${\mathrm{F}}^{-2\mathrm{}}$ and 45 ${\mathrm{F}}^{-2\mathrm{}}$. Experimental errors range from 3.1% to 5.3%, including a systematic error estimated to be 1.9% added in quadrature. Electric and magnetic form factors are computed from all the recent data in this $q^2$ range, with allowance made for possible normalization differences. The results show a deviation from the scaling law.