Polarization transfer and spin response functions in quasielastic(p→,n→)reactions at 346 MeV

Abstract

A complete set of polarization transfer coefficients has been measured for quasielastic $(\stackrel{\ensuremath{\rightarrow}}{p},\stackrel{\ensuremath{\rightarrow}}{n})$ reactions on ${}^{2}\mathrm{H},$ ${}^{6}\mathrm{Li},$ ${}^{12}\mathrm{C},$ ${}^{40}\mathrm{Ca},$ and ${}^{208}\mathrm{Pb}$ at a bombarding energy of 346 MeV and a laboratory scattering angle of $22\ifmmode^\circ\else\textdegree\fi{}$ ${(q}_{\mathrm{lab}}\ensuremath{\approx}1.7 {\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}).$ The spin-longitudinal ${R}_{L}$ and spin-transverse ${R}_{T}$ response functions are extracted within a framework of a plane-wave impulse approximation with eikonal and optimal factorization approximations. The theoretically expected enhancement of ${R}_{L}{/R}_{T}$ is not observed. The observed ${R}_{L}$ is consistent with the pionic enhanced ${R}_{L}$ expected by random-phase approximation (RPA) calculations. On the contrary, a large excess of the observed ${R}_{T}$ is found in comparison with ${R}_{T}$ of the quasielastic electron scattering as well as of RPA calculations. This excess masks the effect of pionic correlations in ${R}_{L}{/R}_{T}.$ The theoretical calculations are performed in a distorted-wave impulse approximation with RPA correlations, which indicates that the nuclear absorption effect depends on the spin direction. This spin-direction dependence is responsible in part for the excess of ${R}_{T}.$