Integrating holographic vector dominance to hidden local symmetry for the nucleon form factor

Abstract

We derive a two-parameter formula for the electromagnetic form factors of the nucleon described as an instanton by "integrating out" all KK modes other than the lowest mesons from the infinite-tower of vector mesons in holographic QCD while preserving hidden local symmetry for the resultant vector fields. With only two parameters, the proton Sachs form factors can be fit surprisingly well to the available experimental data for momentum transfers $Q^2\lsim 0.5$ GeV$^2$ with $\chi^2$/dof $\lsim 2$. We interpret this agreement as indicating the importance of an infinite tower in the soliton structure of the nucleon. The prediction of the Sakai-Sugimoto holographic dual model is checked against the fit values to assess its accuracy in describing the proton structure. We find that the structure of the "core" of roughly 1/3 in the proton size indicated in experiments and commonly associated with an intrinsic quark-gluon structure in QCD is "hidden" in the infinite tower in the holographic model.