Electromagnetic form factors of the nucleon in chiral perturbation theory

The electromagnetic form factors of the nucleon are calculated at order q⁴ in a manifestly Lorentz-invariant formulation of baryon chiral perturbation theory. In order to obtain a consistent power counting for the renormalized diagrams, we make use of the extended on-mass-shell renormalization scheme which we have discussed in a recent paper. We analyse the Dirac and Pauli form factors, F₁ and F₂, as well as the electric and magnetic Sachs form factors, G_E and G_M. Our results are compared with those obtained in the heavy-baryon approach and in the infrared regularization. In addition, the Sachs form factors are compared with experimental data. We confirm previous findings that a one-loop calculation of the electromagnetic form factors does not generate sufficient curvature for the Sachs form factors G^p_E, G^p_M and Gⁿ_M. Moreover, the electric form factor of the neutron is very sensitive to higher-order contributions.