np Pair transfer mechanism for backward elastic p He-3 scattering at intermediate energies

The two-body transfer mechanism for elastic rearrangement scattering from the three-body bound state i + {jkl} --> j + {ikl} has been investigated on the basis of 4-dimensional formalism of covariant nonrelativistic graphs. The relation between this approach and the S-dimensional graph formalism has been analyzed in detail. This approach is applied to describing backward elastic p He-3 scattering in the energy range 0.5-1.7 GeV. The Faddeev 5-channel wave function is used for the bound state of the He-3 nucleus. Numerical calculations show that the mechanism of sequential transfer of a noninteracting np-pair dominates while transfer of an interacting pair as well as nonsequential transfer of a noninteracting np-pair give a negligible contribution, The dominating mechanism is insensitive to the D-components of the He-3 wave function and relativistic effects in spite of high momentum transfer. Taking into consideration Glauber rescatterings in the entrance and exit channels one obtains agreement with the experimental data in energy and angular dependence of the differential cross section at energies 0.9- 1.7 GeV.