Manifestly-covariant chiral PT calculation of nucleon Compton scattering
Abstract
We compute the Compton scattering off the nucleons in the framework of manifestly covariant baryon chiral perturbation theory (B). The results for observables differ substantially from the corresponding calculations in heavy-baryon chiral perturbation theory (HB), most appreciably in the forward kinematics. We verify that the covariant p3 result fulfills the forward-Compton-scattering sum rules. We also explore the effect of the (1232) resonance at order p4/, with ≈ 300 MeV, the resonance excitation energy. We find that the substantial effect of the -excitation on the nucleon polarizabilities can naturally be accommodated in the manifestly covariant calculation.
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