Delta(1232) and the polarizabilities of the nucleon

Previous calculations of the polarizabilities of the nucleon within the framework of heavy baryon chiral perturbation theory have included the contribution of the Delta(1232) only in its effects on various contact terms or have been performed in chiral SU(3) where systematic errors are difficult to control. Herein, we perform a corresponding calculation in chiral SU(2) wherein Delta(1232) is treated as an explicit degree of freedom and the expansion is taken to third order in soft momenta the pion mass, and the quantity M-Delta-M-N, collectively denoted epsilon. We present the results of a systematic 0(epsilon(3)) calculation of forward Compton scattering off the nucleon, extract the electric polarizability <(alpha(E))over bar>, the magnetic polarizability <(beta(M))over bar>, and the spin polarizability gamma, and compare with available information from experiments and from previous calculations. Concluding with a critical discussion of our results. we point out the necessity of a future O(epsilon(4)) calculation.