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

We compute the differential yield for quark anti-quark dijet production in high-energy electron-proton and electron-nucleus collisions at small x as a function of the relative momentum P-perpendicular to and momentum imbalance k(perpendicular to) of the dijet system for different photon virtualities Q(2), and study the elliptic and quadrangular anisotropies in the relative angle between P-perpendicular to and k(perpendicular to). We review and extend the analysis in [1], which compared the results of the Color Glass Condensate (CGC) with those obtained using the transverse momentum dependent (TMD) framework. In particular, we include in our comparison the improved TMD (ITMD) framework, which resums kinematic power corrections of the ratio k(perpendicular to) over the hard scale Q(perpendicular to). By comparing ITMD and CGC results we are able to isolate genuine higher saturation contributions in the ratio Q(s)/Q(perpendicular to) which are resummed only in the CGC. These saturation contributions are in addition to those in the Weizsacker-Williams gluon TMD that appear in powers of Q(s)/k(perpendicular to). We provide numerical estimates of these contributions for inclusive dijet production at the future Electron-Ion Collider, and identify kinematic windows where they can become relevant in the measurement of dijet and dihadron azimuthal correlations. We argue that such measurements will allow the detailed experimental study of both kinematic power corrections and genuine gluon saturation effects.

Automated summary

This study focuses on computing the differential yield for quark anti-quark dijet production in high-energy electron-proton and electron-nucleus collisions at small x. It compares results between the Color Glass Condensate (CGC) and the improved TMD (ITMD) frameworks, highlighting genuine higher saturation contributions. The study provides numerical estimates for inclusive dijet production at the future Electron-Ion Collider, aiming to allow detailed experimental study of kinematic power corrections and genuine gluon saturation effects.