Incoherent Electron Scattering from the Nucleons in Beryllium and Carbon and the Magnetic Size of the Neutron

The electron scattering at high momentum transfer has been measured from the nucleons in Be, in C, and from the free proton. The data yield the cross section of the average nucleon and of the neutron in relation to that of the proton. $\frac{{\sigma }_n}{{\sigma }_p\left(\theta \right)}$ is found to be 1.16±0.3 at 500 Mev and 135°; it decreases, as expected, for smaller angles and lower energies. If the assumption is made that meson-exchange effects and interactions in the final state are not important, the form factors obtained indicate an apparent root-mean-square radius of the neutron's magnetic-moment distribution of (0.53±0.15)×${10}^{-13\mathrm{}}$ cm. It is possible that the apparent small size of the neutron in Be and C is due to the neglect of meson-exchange effects and interactions in the final state. The present result is smaller than a neutron size, given by Yearian and Hofstadter, who compared the cross sections of deuteron and proton and found equal sizes for neutron and proton. If one accepts the latter result, the present experiment can be used to yield a measure of the above neglected effects.