Investigating Generalized Parton Distribution in Gravity Dual

Understand

Generalized parton distribution (GPD) contains rich information of partons in a hadron, including transverse profile, and is also non-perturbative information necessary in describing a variety of hard processes, such as meson leptoproduction and double deeply virtual Compton scattering (DDVCS).

• In order to unveil non-perturbative aspects of GPD, we study DDVCS at small $x$ in gravitational dual description.
• Using the complex spin $j$-plane representation of DDVCS amplitude, we show that GPD is well-defined and can be extracted from the amplitude even in the strong coupling regime.
• It also turns out that the saddle point value in the $j$-plane representation plays an important role; there are two phases in the imaginary part of the amplitude of DDVCS and GPD, depending on relative position of the saddle point and the leading pole in the $j$-plane, and crossover between them is induced by the change of the kinematical variables.