Color charge correlations in the proton at NLO: beyond geometry based intuition

Abstract

Color charge correlators provide fundamental information about the proton structure. In this Letter, we evaluate numerically two-point color charge correlations in a proton on the light cone including the next-to-leading order corrections due to emission or exchange of a perturbative gluon. Our results show that the correlator exhibits startlingly non-trivial behavior at large momentum transfer or central impact parameters, and that the color charge correlation depends not only on the impact parameter but also on the relative transverse momentum of the two gluon probes and their relative angle. Furthermore, from the two-point color charge correlator, we compute the dipole scattering amplitude. Its azimuthal dependence differs significantly from a impact parameter dependent McLerran-Venugopalan model based on geometry. Our results also provide initial conditions for Balitsky-Kovchegov evolution of the dipole scattering amplitude. These initial conditions depend not only on the impact parameter and dipole size vectors, but also on their relative angle and on the light-cone momentum fraction x in the target.

The importance of kinematic twists and genuine saturation effects in dijet production at the Electron-Ion Collider

“…Here, at the initial x = 0.01 the functional form of the dipole operator (in case of proton targets) is obtained from a McLerran-Venugopalan model [12] based parametrization and written as (see also Refs. [100,101])…”

Exclusive heavy vector meson production at next-to-leading order in the dipole picture

“…These applications include, for example, a successful description of the structure function [20,21] and vector meson production data [22][23][24][25][26][27][28][29][30][31] measured at HERA [32][33][34] and in Ultra Peripheral collisions [17,35] at the LHC [36][37][38][39][40]. In recent years, the theory has been developed towards nextto-leading order accuracy, including derivations of the next-to-leading order evolution equations [41][42][43][44][45] with perturbative corrections to initial conditions [46,47], and impact factors for structure functions [48][49][50][51][52], exclusive [53,54] and inclusive particle production [55][56][57][58][59][60][61][62].…”