The πN scattering in nuclear matter

The effect of a nuclear medium on the πN scattering amplitude is discussed in a general formalism. A double-counting problem coming from the usual definition of the density-dependent πN scattering amplitude is resolved in this framework. We study the corrections to the fourth-order Chew-Low amplitude. It is shown that the leading terms of the Pauli correction cancel to this order, when one includes the Pauli effect in all intermediate states. The effect of a nuclear medium at nuclear matter density is found to be a 12 % quenching of the amplitude at threshold.