Relativistic three-body calculation ofπdscattering

Abstract

We present a unitary, Lorentz-invariant three-body calculation of pion-deuteron elastic scattering, based upon the idea of quasiparticle-dominated two-body interactions. We make detailed comparisons of these results with those of a conventional fixed-scatterer approach and find that the fixed-nucleon calculation does not adequately reproduce the three-body results, demonstrating the importance of properly treating the three-body kinematics (i.e., of including nucleon recoil and isobar propagation). The multiple scattering expansion converges much more rapidly in the three-body approach than in the fixed-scatterer calculation. Intermediate nucleon-nucleon interactions play an important role, giving contributions to the scattering amplitude of the same order as those given by pion multiple scattering; these effects are especially significant for back-angle scattering. Finally, we compare our results with the available experimental data for the $\pi d$ total and integrated elastic cross sections and obtain good agreement. Nucleon spin is neglected in all calculations.