Timelike and spacelike nucleon electromagnetic form factorsbeyond relativistic constituent quark models

摘要

For the first time, a phenomenological analysis of the experimental electromagnetic form factors of thenucleon, both in the timelike and spacelike regions, is performed by taking into account the effectsof nonvalence components in the nucleon state, within a light-front framework. Our model, based onsuitable ansatzes for the nucleon Bethe-Salpeter amplitude and a microscopic version of the well-knownVector Meson Dominance model, has only four adjusted parameters (determined by the spacelike datawith X~2/datum~ 1.7), and yields a nice description of the experimental electromagnetic form factors inthe physical region in the range —30 (GeV/c)~2< q~20 (GeV/c)~2, except for the neutron one in thetimelike region. Valuable information can be gained in the timelike region on possible missing VectorMesons around q~2~4.5 (GeV/c)~2and q~28.0 2.