Duality between different mechanisms of QCD factorization in \gamma^*\gamma collisions

TL;DR

This paper investigates the duality between different QCD factorization mechanisms in gamma* gamma collisions, highlighting how duality depends on the nonperturbative models used and identifying two distinct regimes involving twist-3 and leading-twist distribution amplitudes.

Contribution

It reveals the presence of duality between two QCD factorization mechanisms in gamma* gamma processes and shows how this duality depends on the nonperturbative modeling approach.

Findings

Duality observed in the scalar phi^3_E model.

Duality in QCD is sensitive to the nonperturbative model.

Two regimes of factorization linked to different nonperturbative mechanisms.

Abstract

We study the phenomenon of duality in hard exclusive reactions to which QCD factorization applies. Considering "two-photon"-like processes in the scalar $\phi^3_E$ model and also hadron-pair production from the collisions of a real (transversely polarized) and a highly virtual, longitudinally polarized, photon in QCD, we identify two regimes of factorization each of them associated with a distinct nonperturbative mechanism. One mechanism involves twist-3 Generalized Distribution Amplitudes, whereas the other one employs leading-twist Transition Distribution Amplitudes. In the case of the scalar $\phi^3_E$ model, we find duality in that kinematical region where the two mechanisms overlap. In the QCD case, the appearance of duality is sensitive to the particular nonperturbative model applied and can, therefore, be used as an additional adjudicator.