Probing nucleon structure via high energy elastic scattering

Analyses of high energy elastic pp and p-bar p scattering data from CERN ISR and SPS Collider seem to provide strong evidence in favor of the gauged nonlinear σ-model of the nucleon. This model describes the nucleon as a topological soliton and introduces the vector mesons ω, ρ, a1 as gauge bosons. The model, however, needs to be extended to include an explicit quark sector, where left and right quarks interact via a scalar field. A critical behavior of the scalar field results in a phase transition to a condensed quark-antiquark ground state. The latter can provide the outer cloud of the nucleon, which is responsible for diffraction scattering. If the nucleon is probed deeper via high energy elastic scattering, then evidence for the phase transition may emerge from a rapid change in the behavior of dσ/dt. (author)