Some hadronic parameters of charmonia in $\boldsymbol{N_{\text{f}}=2}$ lattice QCD
The phenomenology of leptonic decays of quarkonia holds many interesting features: for instance, it can establish constraints on scenarios beyond the Standard Model with the Higgs sector enriched by a light CP-odd state. In the following paper, we report on a two-flavor lattice QCD study of the $\eta_c$ and $J/\psi$ decay constants, $f_{\eta_c}$ and $f_{J\psi}$. We also examine some properties of the first radial excitation $\eta_c(2S)$ and $\psi(2S)$.