We present analyses on nucleon structure functions at small Bjorken $x$ in the framework of holographic QCD. In this study, we improve the description of the target nucleon in the current setup of the holographic model by introducing a soft-wall AdS/QCD model, in which the anti–de Sitter geometry is smoothly cut off at the infrared boundary. Combining the improved Pomeron-nucleon coupling and the wave function of the five-dimensional U(1) vector field with the Brower-Polchinski-Strassler-Tan Pomeron exchange kernel, we obtain the structure functions. Here we focus on the nonperturbative kinematical region, where ${10}^{-6}\le x\le {10}^{-2}$ and $Q^2\le$ a few (${\mathrm{GeV}}^2$), and show that our calculations for $F_2^p$ and $F_L^p$ are consistent with experimental data of the deep inelastic scattering at HERA. Furthermore, we find that the resulting longitudinal-to-transverse ratio of the structure functions, $F_L^p/F_T^p$, depends on both $x$ and $Q^2$.

• Received 26 December 2013

DOI:https://doi.org/10.1103/PhysRevD.89.115015