Finite-size effects on small-$x$ evolution and saturation in proton and nuclear targets

Abstract

Within the Color Glass Condensate effective field theory, we assess the importance of including a finite size for the target on observables sensitive to small-$x$ evolution. To this end, we study the Balitsky-Kovchegov (BK) equation with impact-parameter dependence in the initial condition. We demonstrate that neglecting the dependence on the impact parameter can result in overestimated saturation effects for protons, while it has little effect for heavy nuclei at the energies available at current experiments. When fixing the nonperturbative parameters to the energy dependence of the exclusive $J/\psi$ photoproduction cross section with proton targets, predictions for lead targets are not sensitive to the applied running-coupling prescription, the scheme chosen to resum large transverse logarithms in the BK equation, or the infrared regulator in the evolution.

16 pages, 19 figures; v2: updated Fig. 8, matches published version

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Cited by in corpus (9)

• Global Bayesian Analysis of $\mathrm{J}/\psi$ Photoproduction on Proton and Lead Targets
• Initial condition for the Balitsky-Kovchegov equation at next-to-leading order
• The energy dependence of exclusive heavy vector meson photoproduction cross-sections and NLO BFKL evolution
• Determination of the initial condition for the Balitsky-Kovchegov equation with transformers
• Non-linear corrections to the derivative of nuclear reduced cross-section at small $x$ at a future electron-ion collider
• Observation of coherent $\varphi$(1020) meson photoproduction in ultraperipheral PbPb collisions at $\sqrt{s_{\text{NN}}}$ = 5.36 TeV
• A numerical implementation of the NLO DIS structure functions in the dipole picture
• Longitudinal Structure Function at the Limit $x=Q^2/s$
• Evaluating the ratio of the exclusive vector meson photoproduction to inclusive hadron/jet production cross section in ultraperipheral heavy ion collisions