Isovector nuclear spin responses from polarization transfer in quasi-free (p,n) reactions at 346 MeV

A complete set of polarization transfer observables has been measured for quasi-free (p vector, n vector) reactions on 2H, 6Li, 12C, 40Ca, and 208Pb at a bombarding energy of 346 MeV and a laboratory scattering angle of 22deg (q = 1.7 fm-1). The data span an energy-loss range of 0-200 MeV. The polarization transfer observables for all five targets are remarkably similar. These polarization observables yield separated spin-longitudinal (σ·q) and spin-transverse (σ x q) nuclear responses. These results are compared to the spin-transverse responses measured in deep-inelastic electron scattering as well as to nuclear responses based on the random phase approximation. Such a comparison reveals an enhancement in the (p vector, n vector) spin-transverse channel, which masks the effect of pionic correlations in the response ratio. (author)