Dynamic versus Static Structure Functions and Novel Diffractive Effects in QCD

TL;DR

This paper explores how initial- and final-state rescattering in QCD significantly influence high-energy scattering phenomena, revealing effects like single-spin asymmetries and diffractive processes that challenge traditional models.

Contribution

It introduces a comprehensive analysis of rescattering effects in QCD, highlighting their impact on observable phenomena and differentiating static from dynamic observables in high-energy physics.

Findings

Rescattering causes single-spin asymmetries and diffractive scattering.

Breakdown of the Lam Tung relation in Drell-Yan reactions.

Direct higher-twist processes explain proton-to-pion ratios in heavy ion collisions.

Abstract

Initial- and final-state rescattering, neglected in the parton model, have a profound effect in QCD hard-scattering reactions, predicting single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, the breakdown of the Lam Tung relation in Drell-Yan reactions, and nuclear shadowing and non-universal antishadowing--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency, and anomalous heavy quark effects. The presence of direct higher-twist processes where a proton is produced in the hard subprocess can explain the large proton-to-pion ratio seen in high centrality heavy ion collisions. I emphasize the importance of distinguishing between static observables such as the probability distributions computed from the square of the light-front wavefunctions versus dynamical observables which include the effects of rescattering.