Eur. Phys. J. C (2009) 61: 357-367
https://doi.org/10.1140/epjc/s10052-009-1010-6

Regular Article - Theoretical Physics

Duality between different mechanisms of QCD factorization in γ ^* γ collisions

¹ Bogoliubov Laboratory of Theoretical Physics, JINR, 141980, Dubna, Russia
² Institut für Theoretische Physik II, Ruhr-Universität Bochum, 44780, Bochum, Germany
³ INFN Gruppo collegato di Cosenza, 87036, Rende, Italy

^* e-mail: anikin@theor.jinr.ru

Received: 19 December 2008
Revised: 3 February 2009
Published online: 8 April 2009

Abstract

We study the phenomenon of duality in hard exclusive reactions to which QCD factorization applies. Considering “two-photon”-like processes in the scalar φ _E ³ model and also two-hadron (pion) 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 φ _E ³ 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.