Determine the dipole–proton cross section from QCD

Determine the dipole–proton interaction cross section for large dipole transverse sizes from first-principles QCD, including its possible low-x saturation behavior.

Background

In the dipole formulation, the virtual photon fluctuates into a quark–antiquark dipole, while the strong-interaction dynamics are encoded in the dipole–proton cross section. At small dipole sizes this cross section can be treated perturbatively, but at larger sizes it becomes sensitive to non-perturbative dynamics and possible saturation of the proton’s parton densities.

The paper notes that phenomenological dipole parametrizations and Color Glass Condensate-inspired models are used to describe the data, but the large-size cross section is not known from first principles. Establishing it would improve the theoretical interpretation of inclusive and exclusive low-x processes.