Anomalous form factor of the neutral pion in an extended AdS/QCD model with Chern-Simons term

We propose an extension of the hard-wall AdS/QCD model by including the Chern-Simons term required to reproduce the chiral anomaly of QCD. In the framework of this holographic model, we study the vertex function F-pi gamma*gamma*(Q(1)(2),Q(2)(2)) which accumulates information about the coupling of the pion to two (in general virtual) photons. We calculate the slope of the form factor with one real and one slightly virtual photon and show that it is close to experimental findings. We analyze the formal limit of large virtualities and establish that predictions of the holographic model analytically (including nontrivial dependence on the ratio of photon virtualities) coincide with those of perturbative QCD calculated for the asymptotic form of the pion distribution amplitude. We also investigate the generalized vector-meson-dominance structure of F-pi gamma*gamma*(Q(1)(2),Q(2)(2)) in the extended AdS/QCD model.