Covariant calculation of pion-He4elastic scattering in the (3, 3) resonance region

Differential cross sections for ${\pi }^{-}{-}^4\mathrm{He}$ elastic scattering were calculated at energies between 110 and 260 MeV. The analysis is completely novel since we have used a covariant multiple scattering theory, and a complete integration over the motion of the target particles has been carried out (instead of invoking the fixed-scatterer approximation). The full dynamical effects of nuclear binding and Fermi motion are considered as well as some modification of the free $\pi N$ interaction. Theoretical results are in good agreement with the data.