Electron Scattering from the Proton

Abstract

We have recently put into operation a new large double-focusing magnetic spectrometer capable of analyzing electrons or other singly-charged particles up to a momentum value of 1000 Mev/c. This spectrometer is of the 180° type previously used in this laboratory and has a mean radius of curvature of 72 in. We have employed this spectrometer in electron-scattering work on the proton between incident electron energies of 650 Mev and 900 Mev and between scattering angles of 45° and 145°. A typical value of the solid angle employed in detecting electrons is 5.6xlO" 3 steradian. The higher energies (>650 Mev) have been realized by virtue of the recent extension in the length of the Stanford linear accelerator.The 72-in. spectrometer forms part of a twomagnet system; the second part is the 36-in. spectrometer described previously. 1 Figure 1 is a schematic drawing of the two spectrometers in a position in which they are 120° apart. Both spectrometers are arranged so that they can be rotated independently about a common scattering center. We have taken data simultaneously with both spectrometers, usually employing the 36-in. magnet at large angles, e.g., up to 145°. The 36-in. spectrometer can handle scattered electrons only up to 500 Mev/c without excessive deterioration of focusing and we have used the 36-in. spectrometer in these experiments only in the very safe region below 370 Mev/c. Such a procedure limits, and has limited in the past, the ability of this spectrometer in obtaining scattering data at high energies and small angles, 1 ' 2 i.e., in those circumstances where the energy of the scattered electron is high.We have begun to carry out a series of experiments on the proton at various energies and angles with these spectrometers. In both instruments we used Cerenkov counters as detectors. In. Fig. 2(a) we show a typical electron-scattering

Splitting of the Proton Form Factors and Diffraction in the Proton

“…Because of the great interest in the proton form factors and because our data appear to be internally consistent, we wish to present in this paper some conclusions drawn from the experimental results given in the accompanying paper. 4 Our procedure has been to solve for the separate form factors (F 19 F 2 ) at conditions lying between 7.7 ^ q 2 ^ 25 by choosing a pair of experimentally measured cross sections at the same value of q 2 but at different correlated values of energy and angle. We have used the method of intersecting ellipses 5 to find the form factors.…”

Nucleon form factors with2+1flavor dynamical domain-wall fermions

“…Early experiments revealed that the proton is a composite particle [4,5,6,7]: i.e. non-zero Pauli and Dirac mean-squared radii and anomalous magnetic moments were measured among other observables.…”

Structure of Nuclei and Nucleons

“…Recently the extension of the experimental measurements to higher energies (-1.0 Bev) showed that indeed F1 > F2 (see 14). The appropriate detailed behavior is shown in Fig.…”

“…Experimental determination of the form factors can be accomplished, for example, by using the method of intersecting ellipses (12) or by other, equivalent methods based on the relativistic idea that each F is a function only of q, and not of E or 0 separately. The early work on the proton was confirmed by subsequent studies at higher energies (~ 600 Mev) (see 13,14), but these energies were still low enough so that the assumption Ft -Fcould be employed. It was noted in the latter experiments that Fi was slightly greater than F2 at values of q2 = 4f-2, where f = fermi = 10'-' centimeter.…”