Transition from soft- to hard-Pomeron in the structure functions of hadrons at small-$x$ from holography

TL;DR

This paper uses holographic QCD to analyze nucleon and pion structure functions at small Bjorken-x, demonstrating a transition from soft to hard Pomeron behavior consistent with experimental data.

Contribution

It introduces a holographic approach to model the soft-to-hard Pomeron transition in hadron structure functions at small-x.

Findings

Reproduces experimental data for proton and pion structure functions.

Captures the Q^2 dependence of the Pomeron intercept from soft to hard regimes.

Highlights the role of AdS wave functions in Pomeron behavior.

Abstract

We study the nucleon and pion structure functions at small Bjorken-$x$ region in the framework of holographic QCD with a special emphasis on the roles of AdS space wave functions. Using the BPST kernel for the Pomeron exchange and calculating its coupling to target hadrons in the AdS space, we obtain $F_2$ structure functions at the small-$x$. Results for the proton $F^p_2$ as well as the pion $F^\pi_2$ are consistent with experimental data of the deep inelastic scattering and the forward electroproduction of a neutron. Observed $Q^2$ dependence of the Pomeron intercept is well reproduced from soft non-perturbatibve $(Q^2 \sim 0)$ to hard perturbative $(Q^2 \gg 1 GeV^2)$ region. We find the interplay between soft and hard Pomerons is closely related with behavior of AdS wave functions of hadrons and the virtual photon.