Asymptotic gluon density within the color dipole picture in the light of HERA high-precision data

TL;DR

This paper analyzes high-precision HERA data using a color dipole model with an analytical gluon density derived from the double-logarithm approximation, successfully describing various structure functions and exclusive cross sections.

Contribution

It introduces an analytical gluon density based on the double-logarithm approximation within the color dipole formalism, effectively fitting HERA data across a wide Q^2 range.

Findings

Accurately describes the reduced cross section σ_r across a broad Q^2 range.

Provides predictions for F_2^{car{c}}, F_2^{bar{b}}, and F_L that match data.

Successfully reproduces exclusive J/ψ and ρ photoproduction cross sections.

Abstract

We present an analysis of the most precise set of HERA data within the color dipole formalism, by using an analytical gluon density, based on the double-logarithm approximation of the DGLAP equations in the asymptotic limit of the scaling variable, $\sigma=\log{(1/x)}\log{(\log{(Q^2/Q_ 0^2)})}\rightarrow \infty$. Fits to data, including charm and bottom quarks are performed and demonstrate the efficiency of the model in describing the reduced cross section, $\sigma_{r}$, in the wide range $Q^2:(1.5,500)$ GeV$^2$ for two dipole models including parton saturation effects. We also give predictions to $F_{2}^{c\bar{c}}$ , $F_{2}^{b\bar{b}}$ and $F_{L}$, all describing the data reasonably well in the range $Q^2:(2.5,120)$ GeV$^2$. Total cross sections of exclusive photoproduction of $J/\psi$ and $\rho$ are also calculated and successfully compared to HERA data and recent measurements at LHCb.