Relativistic predictions of spin observables for exclusive proton knockout reactions

Within the framework of the relativistic distorted wave impulse approximation (DWIA), we investigate the sensitivity of complete sets of polarization transfer observables (P, Ay, Dnn, Ds′s, Dl′l, Ds′l, and Dl′s), for exclusive proton knockout from the 3s1/2, 2d3/2 and 2d5/2 states in 208Pb, at an incident laboratory kinetic energy of 202 MeV, and for coincident coplanar scattering angles (28.0, −54.6), to different distorting optical potentials, finite-range (FR) versus zero-range (ZR) approximations to the DWIA, as well as medium-modified mesonnucleon coupling constants and meson masses. Results are also compared to the nonrelativistic DWIA predictions based on the Schrödinger equation. For knockout from the 3s1/2 state, Ay, Dnn and Ds′s exhibit large differences between Dirac and Schrödinger-based DWIA models. On the other hand, for knockout from the 2d3/2 state, the most sensitive observables to the latter are Dnn, Dl′s and Dl′l, whereas the corresponding observables for 2d5/2 knockout are Ds′s and Dl′s. The most sensitive observables to ZR versus FR approximations to the DWIA are the induced polarization (P), Dl′s and Ds′l for knockout from the 3s1/2, 2d3/2 and 2d5/2 states, respectively. Although polarization transfer observables are relatively insensitive to different global Dirac optical potential parameter sets, distorting optical potentials are crucial for describing the oscillatory behavior of spin observables. In addition, it is seen that Ay, P and Ds′s are very sensitive to reductions in the meson-coupling constants and meson masses by the nuclear medium for proton knockout from all three states. PACS numbers: PACS number(s): 24.10.Jv, 24.70.+s, 25.40.-h