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

Understand

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.