Gravitational form factors of the proton in the improved holographic QCD model

Abstract

We compute the gluonic contribution to the gravitational form factors of the proton using the improved holographic QCD model, in which the proton is described in terms of bulk Dirac fermions. Model parameters are constrained using lattice and phenomenological input, allowing us to obtain estimates for the gravitational form factors and to compare them with results from other approaches. The resulting gluonic contribution to the $\mathcal{D}(t)$ form factor is found to exhibit an infrared pole in our framework. Using the extracted form factors, we analyze mechanical properties of the proton, including pressure and shear distributions. We obtain estimates of $\rho_{\text{mech}} = 0.95$ fm and $\rho_{\text{mass}} = 0.61$ fm for the mechanical and the mass radii of the proton, respectively, which are similar to other nonperturbative studies.