Paper detail

On Nucleon Electromagnetic Form Factors

A Poincare&#39; covariant Faddeev equation, which describes baryons as composites of confined-quarks and -nonpointlike-diquarks, is solved to obtain masses and Faddeev amplitudes for the nucleon and Delta. The amplitudes are a component of a nucleon-photon vertex that automatically fulfills the Ward-Takahashi identity for on-shell nucleons. These elements are sufficient for the calculation of a quark core contribution to the nucleons&#39; electromagnetic form factors. An accurate description of the static properties is not possible with the core alone but the error is uniformly reduced by the incorporation of meson-loop contributions. Such contributions to form factors are noticeable for Q^2 < ~2 GeV^2 but vanish with increasing momentum transfer. Hence, larger Q^2 experiments probe the quark core. The calculated behaviour of G_E^p(Q^2)/G_M^p(Q^2) on Q^2 \in [2,6] GeV^2 agrees with that inferred from polarisation transfer data. Moreover, \sqrt{Q^2} F_2(Q^2)/F_1(Q^2) is approximately constant on this domain. These outcomes result from correlations in the proton&#39;s amplitude.