Spin and Polarization in High-Energy Hadron-Hadron and Lepton-Hadron Scattering

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.

Special Issue: Advances in Spin Physics

“…Recent advances in spin physics have led to a proposal of using storage rings for the search of axion-like particles, which are one of the candidates for explaining the dark matter in the Universe. The details of spin degrees role, its studies and perspectivesstudies of these can be found in [3][4][5][6][7].…”

“…The Reference [3] reviews the role of spin in high energy hadron-hadron and leptonhadron interactions. It concerns mainly the nonperturbative sector of QCD, the roles of pomeron, odderon, unitarity, analyticity for spin observables and dependence of differential cross-section on the Mandelstam variables s and t with emphasis on Regge trajectories.…”