Relativistic predictions of spin observables for exclusive proton knockout reactions

Abstract

We demonstrate the ability of complete sets of exclusive $(\stackrel{\ensuremath{\rightarrow}}{p},2\stackrel{\ensuremath{\rightarrow}}{p})$ polarization transfer observables to discriminate between different model ingredients of the relativistic distorted wave impulse approximation (DWIA). Spin observables are identified, which are sensitive to Dirac versus Schr\"odinger dynamical equations of motion, different distorting optical potentials, finite-range versus zero-range approximations to the DWIA, as well as medium-modified meson-nucleon coupling constants and meson masses. In particular, we consider the knockout of protons from the ${3s}_{1/2},$ ${2d}_{3/2},$ and ${2d}_{5/2}$ states in ${}^{208}\mathrm{Pb},$ at an incident laboratory kinetic energy of 202 MeV, and for coincident coplanar scattering angles (28.0\ifmmode^\circ\else\textdegree\fi{}, -54.6\ifmmode^\circ\else\textdegree\fi{}). The reaction kinematics are chosen so as to maximize the influence of distortion effects, while still maintaining the validity of the impulse approximation, and also avoiding complications associated with the inclusion of recoil corrections in the relativistic Dirac equation.