Quasifree(e,e′p)Reactions and Proton Propagation in Nuclei

Abstract

The (e, e 0 p) reaction was studied on targets of C, Fe, and Au at momentum transfers squared Q 2 of 0.6, 1.3, 1.8, and 3.3 GeV 2 in a region of kinematics dominated by quasifree electron-proton scattering. Missing energy and missing momentum distributions are reasonably well described by plane wave impulse approximation calculations with Q 2 and A dependent corrections that measure the attenuation of the final state protons. [S0031-9007 (98) The (e, e 0 p) reaction with nearly free electron-proton kinematics (quasifree) has proven to be a valuable tool to study the propagation of nucleons in the nuclear medium [1][2][3]. The relatively weak interaction of the electron with the nucleus allows the electrons to penetrate the nuclear interior and knock out protons. These studies complement nucleon-induced measurements of proton propagation in nuclei which give more emphasis to the nuclear surface. This paper reports the first results of a systematic study of the quasifree knockout of protons of 300-1800 MeV kinetic energy from carbon, iron, and gold targets. This energy range includes the minimum of the nucleon-nucleon (N-N) total cross section, the rapid rise in this cross section with energy above the pion production threshold, and extends to the long plateau in the energy dependence of the N-N total cross section. These features of the N-N interaction would be expected to be reflected in the energy dependence of attenuation of protons as they pass 5072 0031-9007͞98͞80(23)͞5072(5)$15.00

Nuclear transparency from quasielasticC12(e,e'p

“…4 are the result of the theory presented in this paper. For comparision also results from previous experiments [1,22,23] for iron and gold are shown. For all three nuclei and large proton kinetic energy (> 1.5 GeV) the theory describes the data well within the error bars.…”

“…4 as a function of the kinetic energy of the proton together with previous results obtained at SLAC [22] (circles) and Jlab [1,23] (squares and diamonds). The error bars shown in the figure contain the statistical and systematic uncertainty but not the modeldependent error.…”

“…On the other hand the data points for gold seem to exceed the theory. For these analyses a correction factor 1/ǫ SRC = 0.78 was used [22,23]. If one would have used the CBF spectral function the results would be lowered by ≈ 7% and thus closer to the theory.…”

“…(20) are shown in table II. When using the CBF The data indicated by circles are from the NE18-experiment at SLAC [22], squares and diamonds are Jlab data of [23] and [1] and from Bates [3] (triangle down). The result indicated by stars is obtained with the correlated spectral function of [8].…”

“…This spectral function factorizes into an E and k distribution for each orbit. It was also used for the analyses of the experiment NE-18 [22] at SLAC and experiments at TJNAF [1,23]. The E-distribution is described by a Lorentzian and the momentum distribution is derived from a Wood-Saxon potential whose parameters are adjusted to data measured at Saclay [24].…”