Pseudoscalar transition form factors and the hadronic light-by-light contribution to the anomalous magnetic moment of the muon from holographic QCD

摘要

We revisit the predictions for the pseudoscalar-photon transition form factors in bottom-up and top-down holographic QCD models which only use the pion decay constant and the ρ meson mass as input. We find remarkable agreement with the available experimental data for the single-virtual π~0 form factor that have recently been extended to lower momenta by BESIII, down to 0.3 GeV~2. The bottom-up models moreover turn out to be roughly consistent with recent experimental results obtained by BABAR for the double-virtual η' form factor at large momenta as well as with dispersion theory results and a recent lattice extrapolation for the double-virtual π~0 form factor. Calculating the pion pole contribution to the hadronic light-by-light scattering in the anomalous magnetic moment of the muon, we find that the bottom-up models in question span the range a_μ~(π~0) =5.9(2)×10~(-10), which is about 10% lower than estimated previously by approximating these holographic predictions through simple interpolators.