  Chiral effective field theory predicts a charge symmetry violating (CSB)
amplitude for pion-nucleon scattering. This mechanism provides a very large
contribution also to the CSB forward-backward asymmetry in the angular
distribution of the reaction pn --> d pi0. This contribution was so large that
it had a potential to cause a large effect also in CSB elastic NN scattering
and to disturb its present understanding. However, it can be seen that,
contrary to pion production, in this case the ud-quark mass difference and the
electromagnetic contribution to the np-mass difference tend to cancel causing
the total effect in the effective range parameters Delta a = a_pp - a_nn and
Delta r_0 = r_0,pp - r_0,nn to be relatively small. In the lowest order and
within the static approximation for the nucleons CSB pion-nucleon rescattering
does not influence np scattering.
