On wave function renormalization and related aspects in heavy fermion effective field theories

We reconsider the question of wave function renormalization in heavy fermio n effective field theories. In particular, we work out a simple and efficie nt scheme to define the wave function renormalization with respect to the l owest order heavy fermion propagator. The method presented is free of a set of ambiguities which arise in heavy fermion effective field theories. In t his context, we discuss the approaches used in the literature so far. We al so calculate the fourth order pion mass contribution to the nucleon mass sh ift and discuss the tree level contributions to the electric Sachs form fac tor of the nucleon.