Study of transition form factors of the lightest pseudoscalars

Abstract In this paper, we study the transition form factors (TFFs) of the lightest pseudoscalar mesons, π 0 , η , and η ′ , within the framework of resonance chiral theory. Our analysis is performed based on the data of time-like and space-like singly-virtual and space-like doubly-virtual form factors, as well as the relevant cross sections and latest invariant mass spectra of e + e − pair for the process of P → γ e + e − . The TFFs of these pseudoscalars are obtained. Also, we evaluate their contributions to the light-by-light part of the anomalous magnetic moment of the muon. Our two fits give similar results, where the better fit (Fit-A) gives a μ π 0 = ( 61.6 ± 1.8 ) × 10 − 11 , a μ η = ( 15.2 ± 1.7 ) × 10 − 11 , a μ η ′ = ( 16.0 ± 1.2 ) × 10 − 11 , and the total contribution of neutral pseudoscalar meson poles is a μ π 0 + η + η ′ =