Gabriel Santiago (Temple U.) [NT/RBRC] Unpolarized GPDs at small x and non-zero skewness
CFNS library
https://bnl.zoomgov.com/j/1614715193?pwd=WkwxODVWdzZzb29zQnZRVGp3VTBDQT09
Generalized parton distributions (GPDs) are one of the primary tools for studying three-dimensional hadron structure in high energy hadron collisions. The GPDs leverage non-zero momentum transfer to probe the three-dimensional spatial structure of hadrons, and are thus defined by off-forward matrix elements of operators in hadron states. At very high energies, GPD sensitive processes can be studied in the small-x / shock wave formalism, where Wilson line correlators provide the primary degrees of freedom encoding the scattering of a colored probe off a hadron target. These correlators are typically insensitive to longitudinal momentum transfer in the eikonal approximation, particularly when considering their rapidity evolution to leading logarithmic accuracy. This means that without corrections the Wilson line correlators will only yield GPDs for zero longitudinal momentum transfer, referred to as GPDs at zero skewness ξ(the fractional longitudinal momentum transfer).
In this talk, we discuss the small-x asymptotics of unpolarized GPDs and GTMDs. Unlike the previous works in the literature, we consider the case of non-zero (but small) skewness while allowing for non-linear contributions to the evolution equations. We show that unpolarized GPDs and GTMDs at small x are related to the eikonal dipole amplitude N, whose small-x evolution is given by the BK/JIMWLK evolution equations, and to the odderon amplitude O, whose evolution is also known in the literature. We show that the effect of non-zero skewness is to modify the value of the evolution parameter (rapidity) in the arguments for the dipole amplitudes N and O from Y = ln(1/x) to Y = ln min {1/|x|,1/|ξ|}.
Yacine Mehtar-Tani