Angular distributions for knockout and scattering of protons in the eikonal approximation.

Abstract

The advent of new electron accelerators with few-GeV beam energies makes the (e,${\mathit{e}}^{\ensuremath{'}}$p) reaction a promising tool for investigating new aspects of the electromagnetic interaction. To this purpose it is crucial to set the scale of final-state interactions (FSI) at high ejectile energies. Usually, the problem is faced by mutuating well-established results of the Glauber method in the framework of elastic (p,p) scattering. Since the generalization of this eikonal approximation to the (e,${\mathit{e}}^{\ensuremath{'}}$p) case is not straightforward, we have analyzed the constraints which make the comparison a meaningful one, using the $^{12}\mathrm{C}$(e,${\mathit{e}}^{\ensuremath{'}}$p${)}^{11}$${\mathrm{B}}_{\mathit{s}1/2}$ and $^{11}\mathrm{B}_{\mathit{s}1/2}$(p,p) reactions with outgoing-proton momenta of 4 GeV/c as a test case. The FSI dominance at large deflection angles produces in the distributions a universal behavior resembling the coherent diffractive scattering between the ejected proton and the (residual) nucleus. Because of the selected sensitivity of the (e,${\mathit{e}}^{\ensuremath{'}}$p) distribution to different theoretical ingredients depending on different values of the deflection angle (or transverse missing momentum), it is argued that the previous comparison with elastic proton scattering may represent a convenient tool to disentangle effects due to the (hard) electromagnetic vertex from (exotic) effects related to the propagation of the struck hadron through the nuclear medium. \textcopyright{} 1996 The American Physical Society.