Probing the γ γ * → η ( ′ ) transition form factors with newly derived η ( ′ ) -meson light-cone distribution amplitudes

In the present work, we analyze the properties of the transition form factors (TFFs) for the γ γ * → η ( ′ ) process, employing the η ( ′ ) -meson light-cone distribution amplitude (LCDA) derived within the light-cone sum rule framework. To this end, we adopt the quark-flavor mixing scheme for the η ( ′ ) meson, and compute the TFFs by systematically incorporating transverse-momentum corrections and contributions beyond the leading Fock state. We utilize light-cone harmonic oscillator models to parametrize the longitudinal and transverse behavior of the leading-twist light-cone wave function, for which the corresponding LCDA exhibits a unimodal profile. We further examine the potential contributions of intrinsic charm components to the scaled TFFs Q 2 F η γ ( Q 2 ) and Q 2 F η ′ γ ( Q 2 ) . Leveraging a range of values for the decay constant f η c 0 and implementing the η – η ′ – η c and η – η ′ – G − η c mixing mechanisms accordingly, together with the recently updated mixing angles, we investigate the impact of the intrinsic c c ¯ and gluonic component on these observables. In the high- Q 2 regime, Q 2 F η ′ γ ( Q 2 ) exhibits a marked increase in sensitivity to the charm quark component, whereas Q 2 F η γ ( Q 2 ) becomes notably stabilized. A detailed discussion of χ 2 / d . o . f . (chi-squared per degree of freedom) and p values