(p7,+)8Li and Li7(p,-)8B reactions at Tp=200 MeV

Angular distributions of the cross sections and analyzing powers for the Li7(p,) reactions leading to the ground and first two excited states of the isobaric analog final nuclei Li8 and B8 have been measured at Tp=200.4 MeV and 199.2 MeV, respectively. The (p,+) cross sections are an order of magnitude larger than those of the (p,-) reaction and exhibit a much stronger angular dependence. The (p,+) analyzing power patterns are essentially state independent and similar to that of the elementary ppd+ reaction near threshold. The analyzing power angular distribution for the Li7(p,-) 8B(2.32 MeV, 3+) transition exhibits a signature characteristic of (p,-) transitions to stretched high-spin two-particle one-hole final states, which is distinctly different from the pattern observed for transitions to low-spin final states. The differences between the two reactions are interpreted in terms of the dynamics of the elementary ppd+ and pnpp- processes.