Duality between different mechanisms of QCD factorization in γ^*γcollisions
arXiv:0806.4551 · doi:10.1140/epjc/s10052-009-1010-6
Abstract
We study the phenomenon of duality in hard exclusive reactions to which QCD factorization applies. Considering "two-photon"-like processes in the scalar 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 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.
14 pages, 8 figures. Substantial changes in the text, 4 figures added, 1 removed; no changes in conclusions