Electron-nucleus Scattering

Abstract

This article presents a review of the field of inclusive quasi-elastic electron-nucleus scattering. It discusses the approach used to measure the data and includes a compilation of data available in numerical form. The theoretical approaches used to interpret the data are presented. A number of results obtained from the comparison between experiment and calculation are then reviewed. The analogies and differences to other fields of physics exploiting quasi-elastic scattering from composite systems are pointed out. I. INTRODUCTIONThe energy spectrum of high-energy leptons (electrons in particular) scattered from a nuclear target displays a number of features. At low energy loss (ω) peaks due to elastic scattering and inelastic excitation of discrete nuclear states appear; a measurement of the corresponding form factors as a function of momentum transfer |q| gives access to the Fourier transform of nuclear (transition) densities. At larger energy loss, a broad peak due to quasi-elastic electron-nucleon scattering appears; this peak -very wide due to nuclear Fermi motion -corresponds to processes where the electron scatters from an individual, moving nucleon, which, after interaction with other nucleons, is ejected from the target. At even larger ω peaks that correspond to excitation of the nucleon to distinct resonances are visible. At very large ω, a structureless continuum due to Deep Inelastic Scattering (DIS) on quarks bound in nucleons appears. A schematic spectrum is shown in Fig. 1. At momentum transfers above approximately 500 MeV/c the dominant feature of the spectrum is the quasi-elastic peak.A number of questions have been investigated using quasi-elastic scattering:• The quasi-elastic cross section integrated over electron energy loss is proportional to the sum of electron-nucleon cross sections. Historically, this has been exploited in order to measure the neutron charge and magnetic form factors using mainly light (A < 4) nuclear targets. Today the emphasis has shifted to exposing possible medium modifications of the nucleon form factors. * Electronic address: benhar@roma1.infn.it † Electronic address: dbd@virginia.edu ‡ Electronic address: ingo.sick@unibas.ch