Benchmark study of the relativistic plane wave impulse approximation for polarized ( p , 2 p ) reactions on the 3 s 1 / 2 state in Pb 208 at 392 MeV

The relativistic plane wave impulse approximation (RPWIA) is benchmarked against the established relativistic distorted wave impulse approximation (RDWIA) for exclusive proton-induced proton knockout reactions ( p ⃗ , 2 p ⃗ ) from the 3 s 1 / 2 state in Pb 208 at 392 MeV . While the RDWIA provides a proper description of the reaction, the RPWIA—which neglects nuclear distortion and absorption effects—fails dramatically for absolute cross sections, requiring a scaling factor of 1 / 26 to match the data. However, within ± 10 MeV of the recoilless condition, the RPWIA quantitatively describes the analyzing power ( A y ) data and yields similar results as the RDWIA predictions for all polarization transfer observables ( D i ′ j ). These polarization transfer observables are insensitive to the choice of the Relativistic Mean Field model used. The study establishes clear boundaries for the RPWIA's utility: Computationally simple predictions for polarization observables near zero recoil, but essential reliance on the RDWIA for spectroscopic factor extraction.