2024/11/15 by Josef Leutgeb, Jonas Mager, Leutgeb, Josef +3 · 2 citations
Physics and Astronomy · #Particle physics theoretical and experimental studies #High-Energy Particle Collisions Research #Dark Matter and Cosmic Phenomena
paper · pdf · doi:10.48550/arxiv.2411.10432
In this paper, we consider hard-wall AdS/QCD models extended by a string-theory inspired Chern-Simons action in terms of a superconnection involving a bi-fundamental scalar field which corresponds to the open-string tachyon of brane-antibrane configurations and which is naturally identified with the holographic dual of the quark condensate in chiral symmetry breaking. This realizes both the axial and chiral anomalies of QCD with a Witten-Veneziano mechanism for the η' mass in addition to current quark masses, but somewhat differently than in the Katz-Schwartz AdS/QCD model used previously by us to evaluate pseudoscalar and axial vector transition form factors and their contribution to the HLBL piece of the muon g-2. Compared to the Katz-Schwartz model, we obtain a significantly more realistic description of axial-vector mesons with regard to f1-f1' mixing and equivalent photon rates. Moreover, predictions of the f1→ e+e- branching ratios are found to be in line with a recent phenomenological study. However, pseudoscalar transition form factors compare less well with experiment; in particular the π0 transition form factor turns out to be overestimated at moderate non-zero virtuality. For the combined HLBL contribution to the muon g-2 from the towers of axial vector mesons and excited pseudoscalars we obtain, however, a result very close to that of the Katz-Schwartz model.