Craig Roberts
Argonne National Labs
USA
Tuesday, April 5, 3.00 pm.
Seminar Room, First Floor Physics Building, University of Adelaide.
Poincare Covariant Faddeev Equation and Nucleon Electromagnetic Form Factors.
Abstract:
Electron scattering at large Q^2 probes a nucleon's quark core. This core's contribution to electromagnetic form factors may be calculated using Poincare covariant Faddeev amplitudes combined with a nucleon-photon vertex that automatically fulfills a Ward-Takahashi identity for on-shell nucleons. The calculated behaviour of G_E^p(Q^2)/G_M^p(Q^2) for Q^2 in the range 2-6 GeV^2 agrees with that inferred from polarisation transfer data, and exhibits a zero at Q^2 approxmately 6.5 GeV^2. There is some evidence that F_2(Q^2)/F_1(Q^2) is propertional to [\ln(Q^2/\Lambda^2)]^2/Q^2 for Q^2 larger than 6 GeV^2.