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We extend our previous calculations of the hadronic light-by-light scattering contribution to the muon anomalous magnetic moment in holographic QCD to models with finite quark masses and a tower of massive pions. Analyzing the role of the latter in the Wess-Zumino-Witten action, we show that the Melnikov-Vainshtein short-distance constraint is satisfied solely by the summation of contributions from the infinite tower of axial-vector meson contributions. There is also an enhancement of the asymptotic behavior of pseudoscalar contributions when their infinite tower of excitations is summed, but this leads only to subleading contributions for the short-distance constraints on light-by-light scattering. We also refine our numerical evaluations, particularly in the pion and a1 sector, which corroborates our previous findings of contributions from axial-vector mesons that are significantly larger than those adopted for the effects of axials and short-distance constraints in the recent white paper on the Standard Model prediction for (g-2)μ. [ABSTRACT FROM AUTHOR]

We revisit the U (1) A anomaly in the holographic model of low-energy QCD by Witten, Sakai, and Sugimoto, presenting a new and direct derivation of the Witten-Veneziano mechanism for generating the mass of the η′ through an anomalous mixing of the Ramond-Ramond C1 field with the singlet component of the pseudoscalar mesons. The latter turns out to have a kinetic mixing with the normalizable modes of the C1 field representing pseudoscalar glueballs, yielding additional vertices for their production and their decay that dominate over those of the unmixed case considered previously in the Witten-Sakai-Sugimoto model. The leading channel is predicted to be a decay into two vector mesons, followed in importance by decay into three pseudoscalar mesons. The issue of production of pseudoscalar glueballs in radiative J/ψ decays and in double diffractive processes is also discussed briefly. [ABSTRACT FROM AUTHOR]

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 π0 form factor that have recently been extended to lower momenta by BESIII, down to 0.3 GeV². 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 π0 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 aμπ0=5.9(2)×10-10, which is about 10% lower than estimated previously by approximating these holographic predictions through simple interpolators. [ABSTRACT FROM AUTHOR]