Color-Dipole Picture versus Hard Pomeron in Deep Inelastic Scattering

TL;DR

This paper compares the Color Dipole Picture and the tensor-Pomeron model in deep inelastic scattering, showing that the CDP aligns with empirical data at high Q^2 and smoothly transitions to photoproduction at low Q^2, highlighting its predictive power.

Contribution

It demonstrates the empirical validity of the Color Dipole Picture at high Q^2 and its smooth transition to photoproduction, contrasting with the tensor-Pomeron model's parameter dependence.

Findings

CDP agrees with empirical data for Q^2 > 20 GeV^2

Predicts a specific energy dependence exponent C_2 ≈ 0.30

Provides a parameter-free transition to photoproduction at low Q^2

Abstract

For photon virtualities of $Q^2 \gsim 20 {\rm GeV}^2$, the results of the (hard Pomeron) fit in the tensor-Pomeron model in terms of the variables $Q^2$ and the virtual-photon-proton energy squared, $W^2$, provide empirical evidence for the validity of the Color Dipole Picture (CDP). Consistency of the CDP with the perturbative QCD (pQCD) improved parton model implies the prediction of $C_2 = \epsilon_0 \cong 0.30$ for the exponent $C_2$ of the energy-squared dependence in agreement with the results of the fits. For $Q^2 \lsim 20 GeV^2$, the CDP yields a parameter-free smooth transition from $Q^2 \gsim 20 {\rm GeV}^2$ to $Q^2 = 0$ photoproduction, in distinction from the tensor-Pomeron model that relies on the additional parameter quantifying the intercept of the soft-Pomeron trajectory.