Longitudinal structure function from the parton parameterization

We present a certain theoretical model to describe data based on the DGLAP evolution equations at low values of x. This model is based on a hard-pomeron exchange in the next-to-next-to-leading order of the perturbative theory. The behavior of the DIS cross section ratio $$R(x,Q^{2})$$ and $$F_{L}(x,Q^{2})/F_{2}(x,Q^{2})$$ is studied and compared with the experimental data. These behaviors are controlled by the color dipole model bound. These results show good agreement with the DIS experimental data throughout the low values of x. The results can be applied to the LHeC region for analyses of ultra-high-energy processes