Dynamic versus Static Hadronic Structure Functions

TL;DR

This paper distinguishes between static and dynamic hadronic structure functions, emphasizing the importance of rescattering effects in deep inelastic scattering and their implications for various QCD phenomena.

Contribution

It highlights the role of rescattering effects in dynamic structure functions, revealing phenomena not captured by static light-front wavefunctions, and reviews their impact on high-energy scattering physics.

Findings

Rescattering effects cause single-spin asymmetries.

Diffractive processes are influenced by initial- and final-state rescattering.

Higher-twist processes explain the proton-to-pion ratio anomaly.

Abstract

"Static" structure functions are the probabilistic distributions computed from the square of the light-front wavefunctions of the target hadron. In contrast, the "dynamic" structure functions measured in deep inelastic lepton-hadron scattering include the effects of rescattering associated with the Wilson line. Initial- and final-state rescattering, neglected in the parton model, can have a profound effect in QCD hard-scattering reactions, producing single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, the breakdown of the Lam-Tung relation in Drell-Yan reactions, nuclear shadowing, and non-universal nuclear antishadowing--novel leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also review how "direct" higher-twist processes -- where a proton is produced in the hard subprocess itself -- can explain the anomalous proton-to-pion ratio seen in high centrality heavy ion collisions.