Energy dependence of the form factor for elastic electron scattering fromC12

Abstract

A static analysis of measurements of C elastic electron-scattering cross sections demonstrates unambiguously the existence of a form-factor energy dependence beyond that due to Coulomb distortion effects. This energy dependence increases smoothly as a function of momentum transfer and incident energy in the region covered by the experiments (1.0( g,s (2.3 fm, 240( Ee (690 MeV).Outside the first diffraction minimum the discrepancies between the form factors deduced from data obtained at different energies are as large as GF0, in the minimum discrepancies as large as 18% have been observed. Including dispersion corrections which are reasonably compatible with this observed energy dependence in the analysis of the data increases the rms charge radius deduced for C by 0.007 to 2.478(9) fm, which is in excellent agreement with the value from muonic x-ray studies.

Untitled

“…The knowledge of the nuclear density distribution (deduced from the charge distribution of the 12 C nucleus [6] shown in Fig. 1 (d)) allows for a further, quantitative analysis of the x F -dependence of this ratio.…”

Quasielastic(e,e′p)reaction onC12

“…One method is to use the inelastic scattering to an excited state whose energy is accurately known to calibrate the dispersion of a spectrometer and then use the calibrated spectrometer to measure the energy of the scattered electron as a function of nuclear target mass. For these measurements a carbon target was used and the dispersion determined by measuring the difference in position of the electrons scattered to the ground and the 4.43891 ± 0.00031 MeV [7] first excited state. A BeO target was then substituted and the energy of the beam, E, determined using the formula:…”

No evidence for medium effects in the12C(e, e'p)11Bg.s. reaction

“…+ n As part of the commisioning of the large-acceptance and high-resolution three-spectrometer setup [1] we have measured the 12C(e,e'p) reaction. Since a Carbon target is easy to handle and to manufacture, this reaction is a good choice for calibration purposes, though not such a large set of accurate 12C(e,e'p) data exists as is the case for the 12C(e,e') reaction [2]. However, there is one set of high quality data measured at NIKHEF [3].…”