Derivation of the Effective Pion-Nucleon Lagrangian within Heavy Baryon Chiral Perturbation Theory

We develop a method for constructing the Heavy Baryon Chiral Perturbation Theory (HBChPT) Lagrangian, to a given chiral order, within HBChPT. We work within SU(2) theory, with only the pion field interacting with the nucleon. The main difficulties, which are solved, are to develop techniques for implementing charge conjugation invariance, and for taking the nucleon on shell, both within the nonrelativistic formalism. We obtain complete lists of independent terms in LHBChPT through O(q3) for offshell nucleons. Then, eliminating equation-of-motion (eom) terms at the relativistic and nonrelativistic level (both within HBChPT), we obtain LHBCHPT for on-shell nucleons, through O(q3). The extension of the method (to obtain on-shell LHBChPT within HBChPT) to higher orders is also discussed. PACS numbers: 11.90.+t, 11.30.-j, 13.75.Gx