Form factors of ηc in light-front quark model

We study the form factors of the ηc meson in the light-front quark model. We explicitly show that the transition form factor of ηc → γ*γ as a function of the momentum transfer is consistent with the experimental data by the BaBar collaboration, while the decay constant of ηc is found to be fηc = 230.5+52.2-61.0 and 303.6+115.2-116.4 MeV for ηc ∝ c anti c by using two ηc → γγ decay widths of 5.3 ± 0.5 and 7.2 ± 2.1 keV, given by Particle Data Group and Lattice QCD calculation, respectively. (orig.)