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 $Q^2$, by quantifying differences between the linear Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution and nonlinear evolution with the Balitsky-Kovchegov (BK) 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 $F_2$ and $F_{\mathrm{L}}$ from both frameworks in a region in $x,Q^2$ 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 $F_2$ remain at a few-percent level, while in $F_{\mathrm{L}}$ the deviations are larger, up to $10\%$ at the EIC and $40\%$ at the LHeC kinematics. With a heavy nucleus the differences are up to $10\%$ in $F_2$, and can reach $20\%$ and $60\%$ in $F_{\mathrm{L}}$ for the EIC and the LHeC, respectively.

14 pages, 11 figures, the coefficients determined in the reweighting process are included in the ancillary files. v2: version is published in Phys. Rev. D

References in corpus (10)

• LHAPDF6: parton density access in the LHC precision era
• The Color Glass Condensate
• NLO evolution of color dipoles
• Quark contribution to the small-$x$ evolution of color dipole
• Mining for Gluon Saturation at Colliders
• Direct numerical solution of the coordinate space Balitsky-Kovchegov equation at next to leading order
• Forward dihadron correlations in deuteron-gold collisions with a Gaussian approximation of JIMWLK
• Forward $J/\psi$ production in proton-nucleus collisions at high energy
• Dipole factorization for DIS at NLO: Combining the $q\bar{q}$ and $q\bar{q}g$ contributions
• Saturation and forward jets in proton-lead collisions at the LHC