Revisiting radiative decays of 1^+- heavy quarkonia in the covariant light-front approach

We revisit the calculation of the width for the radiative decay of a 1^+- heavy Q anti Q meson via the channel 1^+- → 0^-++γ in the covariant light-front quark model. We carry out the reduction of the light-front amplitude in the non-relativistic limit, explicitly computing the leading and next-to-leading order relativistic corrections. This shows the consistency of the light-front approach with the non-relativistic formula for this electric dipole transition. Furthermore, the theoretical uncertainty in the predicted width is studied as a function of the inputs for the heavy-quark mass and wave function structure parameter. We analyze the specific decays h_c(1P) → η_c(1S) + γ and h_b(1P) → η_b(1S) + γ. We compare our results with experimental data and with other theoretical predictions from calculations based on non-relativistic models and their extensions to include relativistic effects, finding reasonable agreement. (orig.)