Nucleon Form Factors in Point-Form Spectator-Model Constructions

Abstract

We discuss electromagnetic currents in the point-form formulation of relativistic quantum mechanics. The construction is along a spectator model and implies that only one quark is explicitly coupled to the photon, but nevertheless many-body contributions are present in the current operator. Such effects are unavoidable in relativistic constructions and resulting ambiguities are notably reduced by imposing charge normalization and time-reversal invariance. The residual theoretical indetermination introduces small but sizeable changes in the nucleon form-factors, particularly at higher Q-squared values, with the data generally centered in the middle of the theoretical band.

Comments: 8 pages, 3 figures, prepared for XI Convegno su Problemi di Fisica Nucleare Teorica, Cortona 2006, 11-14 October 2006