Signatures of gluon saturation from structure-function measurements

Abstract

We study experimentally observable signals for nonlinear QCD dynamics in deep inelastic scattering (DIS) at small Bjorken variable x and moderate virtuality Q2, by quantifying differences between the linear Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution and nonlinear evolution with the Balitsky-Kovchegov equation. To remove the effect of the parametrization freedom in the initial conditions of both equations, we first match the predictions for the DIS structure functions F2 and FL from both frameworks in a region in x, Q2 where both frameworks should provide an accurate description of the relevant physics. The differences in the dynamics are then quantified by the deviations when one moves away from this matching region. For free protons we find that the differences in F2 remain at a few-percent level, while in FL the deviations are larger, up to 10% at the Electron Ion Collider (EIC) and 40% at the Large Hadron-electron Collider (LHeC) kinematics. With a heavy nucleus the differences are up to 10% in F2, and can reach 20% and 60% in FL for the EIC and the LHeC, respectively.