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

Abstract

A complete set of polarization transfer observables was measured for inclusive 500 MeV proton scattering from $^{2}\mathrm{H}$, Ca(nat.), and Pb(nat.) at ${\mathrm{theta}}_{\mathrm{lab}}$=18.5\ifmmode^\circ\else\textdegree\fi{} (q=1.75 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$). 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.