Abstract
The role of spin degrees of freedom in high-energy hadron-hadron and lepton-hadron scattering is reviewed with emphasis on the dominant role of soft, diffractive, non-perturbative effects. Explicit models based on analyticity and Regge-pole theory, including the pomeron trajectory (gluon exchange in the t channel) are discussed. We argue that there is a single, universal pomeron in Nature, manifest as relatively “soft” or “hard”, depending on the kinematics considered. Both the pomeron and the non-leading (secondary) Regge trajectories, made of quarks are non-linear, complex functions. They are populated by a finite number of resonances: known baryons and mesons in case of the reggeons and hypothetical glueballs in case of the pomeron (“oddballs” on the odderon trajectory). Explicit models and fits are presented that may be used in recovering generalized parton distributions from deeply virtual Compton scattering and electoproduction of vector mesons.
Highlights
Interest in spin physics at high-energies was varying with time
One inevitably encounters related problems such as: diffraction and the nature of the pomeron, that could be utilized as made of gluons; reconciling soft and hard aspects of the theory, nucleon structure, revealed in inclusive deep-inelastic scattering (DIS) and exclusive deeply virtual Compton scattering (DVCS) as means to reveal the nucleon structure, closely related to spin and polarization, connecting structure and dynamics
The present paper is a recapitulation of the earlier results by the author, revised, updated and extended with account for the recent developments in the field, especially those connected to “nucleon holography”, based on generalized parton distributions (GPDs)
Summary
Interest in spin physics at high-energies was varying with time. In general, there is a prejudice that the role of spin decreases as energy is increasing. One has to understand the origin of polarization in the scattering of unpolarized hadrons, as for example in Λ production Another issue is the still purely understood delicate mechanism of the diffraction minimum in high-energy proton-proton scattering. The present paper is a recapitulation of the earlier results by the author, revised, updated and extended with account for the recent developments in the field, especially those connected to “nucleon holography”, based on generalized parton distributions (GPDs) Parallel to these practical developments, the still open basic problem of quark confinement is always present in our discussions. The Lambda hyperons produced at “particlization” (fluid to particle transition) hypersurface acquire polarization via a thermodynamic spin-vorticity coupling mechanism This effect is interesting as a possible manifestation of the most vortic fluid ever made. For a much wider panorama we recommend to the reader the excellent papers [2,10,11]
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