Photon-photon collision: ambiguity and duality in QCD factorization theorem

TL;DR

This paper explores duality in two-photon processes within a scalar model and QCD, revealing how different nonperturbative mechanisms can be equivalent and how duality can guide model selection.

Contribution

It demonstrates the presence of duality between distinct nonperturbative mechanisms in two-photon processes and discusses its implications for QCD modeling.

Findings

Duality observed in scalar $ ext{phi}^3_E$ model.

Duality in QCD sensitive to nonperturbative models.

Duality can be used to select appropriate models.

Abstract

We discuss duality in ``two-photon''-like processes in the scalar $\varphi^3_E$ model and also in the process $\gamma^*\gamma\to\pi\pi$ in QCD. Duality implies the equivalence between two distinct nonperturbative mechanisms. These two mechanisms, one involving a twist-3 Generalized Distribution Amplitude, the other employing a leading-twist Transition Distribution Amplitude, are associated with different regimes of factorization. In the kinematical region, where the two mechanisms overlap, duality is observed for the scalar $\varphi^3_E$ model, while in the QCD case the appearance of duality turns out to be sensitive to the particular nonperturbative model applied and can, therefore, be used as a tool for selecting the most appropriate one.