Pauli blocking correction in pion-He4scattering

We discuss the pion nucleon partial wave mixing due to the Pauli projection operator in $\ensuremath{\pi}$-$^{4}\mathrm{He}$ scattering. In a previous numerical investigation we found that this partial wave mixing generates only small corrections in the cross sections. In the present study we demonstrate that the coupling between partial waves vanishes in the limit $\frac{{m}_{\ensuremath{\pi}}}{{m}_{\mathrm{N}}}\ensuremath{\rightarrow}0$, thereby explaining these numerical findings.NUCLEAR REACTIONS $\ensuremath{\pi}$-$^{4}\mathrm{He}$ scattering, optical potential, Pauli principle corrections.