Measurements of elastic electron-proton scattering at large momentum transfer

Measurements of the forward-angle differential cross section for elastic electron-proton scattering were made in the range of momentum transfer from Q²=2.9 to 31.3 (GeV/c)² using an electron beam at the Stanford Linear Accelerator Center. The data span six orders of magnitude in cross section. Combinded statistical and systematic uncertainties in the cross section measurements ranged from 3.6% at low Q² to 19% at high Q². These data have been used to extract the proton magnetic form factor GMᵖ(Q²) and Dirac form factor F₁ᵖ(Q²) by using form factor scaling. The logarithmic falloff of Q⁴F₁ᵖ expected from leading twist predictions of perturbative quantum chromodynamics is consistent with the new data at high Q². Some nonperturbative and hybrid calculations also agree with our results.