Electron-proton Elastic Scattering Cross Sections Research Articles

Electromagnetic form factors of the proton at squared four-momentum transfers between 10 and 50 fm −2

Electron-proton elastic scattering cross sections have been measured to determine the proton electromagnetic form factors at squared four-momentum transfers q 2 between 10 and 50 fm −2. At these values of q 2 we measured angular distributions between 25° and 110° and in addition at 25° and 35° cross sections for q 2 from 2 to 20 fm −2 using the external electron beam of the Bonn 2.5 GeV electron synchrotron. Our results confirm deviations from the scaling law.

Electromagnetic proton form factors at squared four-momentum transfers between 1 and 3 (GeV/ c) 2

Electron-proton elastic scattering cross sections have been measured at four-momentum transfers between 1.0 and 3.0 (GeV/ c) 2 and at electron scattering angles between 10° and 20° and at about 86° in the laboratory. The proton electromagnetic form factors G E and G M were determined. The results indicate that G E( q 2) decreases faster with increasing q 2 than G M( q 2).

Measurement of the ratio of the proton form factors, G E/G M, at high momentum transfers and the question of scaling

Electron-proton elastic scattering cross sections have been measured at the Stanford Linear Accelerator Center at four-momentum transfers squared (q 2) of 1.0, 1.5, 2.0, 2.5and 3.75 (GeV/ c) 2. The angular distributions at q 2 = 2.5 and 3.75 (GeV/ c) 2are sufficient to provide values of the ratio G E/ G Mindependent of the results from other laboratories. Our results are compatible with scaling, G E(q 2) = G M(q 2)/ μ, within the experimental errors.

Comparison of Electron-Proton and Positron-Proton Elastic Scattering at Four-Momentum Transfers up to 5.0(GeV/c)2

Measurements of the ratio ($R$) of positron-proton and electron-proton elastic-scattering cross sections have been made, with the square of the four-momentum transfer (${q}^{2}$) equal to 0.20, 0.69, 0.73, 1.54, 2.44, 3.27, 3.79, and 5.00 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$. The measurements, after radiative corrections, are consistent with $R=1$, with standard errors ranging from \ifmmode\pm\else\textpm\fi{}0.016 to \ifmmode\pm\else\textpm\fi{}0.123. The results give limits for the size of the two-photon effects.