  The relativistic chiral SU(3) Lagrangian is used to describe kaon-nucleon
scattering imposing constraints from the pion-nucleon sector and the
axial-vector coupling constants of the baryon octet states. We solve the
covariant coupled-channel Bethe-Salpeter equation with the interaction kernel
truncated at chiral order Q^3 where we include only those terms which are
leading in the large N_c limit of QCD. The baryon decuplet states are an
important explicit ingredient in our scheme, because together with the baryon
octet states they form the large N_c baryon ground states of QCD. Part of our
technical developments is a minimal chiral subtraction scheme within
dimensional regularization, which leads to a manifest realization of the
covariant chiral counting rules. All SU(3) symmetry-breaking effects are well
controlled by the combined chiral and large N_c expansion, but still found to
play a crucial role in understanding the empirical data. We achieve an
excellent description of the data set typically up to laboratory momenta of
p_lab about 500 MeV.
