Baryon chiral perturbation theory using a heavy fermion lagrangian

Baryon chiral perturbation theory is developed using an effective lagrangian in which the baryons appear as heavy static fields. The chiral logarithmic corrections to the axial current for semileptonic hyperon decay and for the analysis of the strangeness content of the proton are computed as examples. The corrections are as big as the lowest order values, which implies that F and D cannot be reliably extracted from hyperon semileptonic decays. (orig.)