Systematic 1M expansion for spin 32 particles in baryon chiral perturbation theory

Starting from a relativistic formulation of the pion-nucleon-delta system, the most general structure of 1M corrections for a heavy baryon chiral lagrangian including spin 32 resonances is given. The heavy components of relativistic nucleon and delta fields are integrated out and their contributions to the next-to-leading order lagrangians are constructed explicitly. The effective theory obtained admits a systematic expansion in terms of soft momenta, the pion mass mπ and the delta-nucleon mass difference Δ. As an application, we consider neutral pion photoproduction at threshold to third order in this small scale expansion.