pi N scattering and electromagnetic corrections in the perturbative chiralquark model

We apply the perturbative chiral quark model to give predictions for the el ectromagnetic O (p(2)) low-energy couplings of the ChPT effective Lagrangia n that define the electromagnetic mass shifts of nucleons and first-order ( e(2)) radiative corrections to the piN scattering amplitude. We estimate th e leading isospin-breaking correction to the strong energy shift of the pi (-)p atom in the 1s state, which is relevant for the experiment "Pionic Hyd rogen" at PSI. (C) 2001 Elsevier Science B.V. All rights reserved.