Manifestly-covariant p3 calculation of nucleon Compton scattering
V. Lensky+*, V. Pascalutsa+∇
PACS: 13.60.Fz, 14.20.Dh, 25.20.Dc
Abstract
We compute the Compton scattering off the nucleons in the
framework of manifestly covariant baryon chiral perturbation
theory (BχPT). The results for observables
differ substantially from the corresponding calculations in heavy-baryon
chiral perturbation theory (HBχPT), 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 Δ(1232) resonance at order p4/Δ, with
MeV, the resonance excitation energy. We find that the
substantial effect of the Δ-excitation on the nucleon polarizabilities
can naturally be accommodated in the
manifestly covariant calculation.