Twist corrections to exclusive vector meson production in a saturation framework

We develop a framework combining the higher-twist formalism of exclusive processes in the s channel with the semiclassical effective description of small-x physics in the t channel. We apply it to transversely polarized light vector meson production, γ∗p→V(ρ,φ,ω)p, which starts at the next-to-leading power and for which a purely collinear treatment leads to end-point singularities. The result is obtained in the most general kinematics, including both forward and nonforward cases by preserving the full impact parameter dependence in the nonperturbative correlators, in both momentum and coordinate space representations. A systematic expansion of the Wilson lines in terms of Reggeized gluon fields is performed in order to obtain the results in the weak-field BFKL approximation. These new results will allow for investigating the dilute-to-dense regime transition of quantum chromodynamics for a wide class of observables.