Continuum polarization transfer in 500 MeV proton scattering and pionic collectivity in nuclei

A complete set of polarization transfer observables was measured for inclusive 500 MeV proton scattering from ²H, Ca(nat.), and Pb(nat.) at theta_lab=18.5° (q=1.75 fm^-1). The excitation energy ranged over the entire quasielastic peak from 20 to 100 MeV. Longitudinal and transverse spin-flip probabilities were extracted from the data. These have simple model-dependent connections to the spin-longitudinal and transverse response functions for the heavy targets. Detailed analysis of the data reveals no evidence for collective enhancement in the spin-longitudinal response function. The relation of this analysis to the interpretation of the European Muon Collaboration effect in terms of excess pions is discussed in detail.