Skewness Dependence of GPD / DVCS, Conformal OPE and AdS/CFT Correspondence II: a holographic model of GPD

Abstract

Traditional idea of Pomeron/Reggeon description for hadron scattering is now being given theoretical foundation in gravity dual descriptions, where Pomeron corresponds to exchange of spin-$j \in 2\mathbb{Z}$ states in the graviton trajectory. Deeply virtual Compton scattering (DVCS) is essentially a 2 to 2 scattering process of a hadron and a photon, and hence one should be able to study non-perturbative aspects (GPD) of this process by the Pomeron/Reggeon process in gravity dual. We find, however, that even one of the most developed formulations of gravity dual Pomeron (Brower--Polchinski--Strassler--Tan (BPST) 2006) is not able to capture skewness dependence of GPD properly. In Part I (arXiv:1212.3322), therefore, we computed Reggeon wavefunctions on AdS$_5$ so that the formalism of BPST can be generalized. In this article, Part II, we use the wavefunctions to determine the DVCS amplitude, bring it to the form of conformal OPE/collinear factorization, and extract a holographic model of GPD, which naturally fits into the framework known as "dual parametrization" or "(conformal) collinear factorization approach".