Radiative corrections to the η(′) Dalitz decays

We provide the complete set of radiative corrections to the Dalitz decays eta(()'()) -> l(+)l(-)gamma beyond the softphoton approximation, i. e., over the whole range of the Dalitz plot and with no restrictions on the energy of a radiative photon. The corrections inevitably depend on the eta(()'()) -> gamma*gamma(*) transition form factors. For the singly virtual transition form factor appearing, e.g., in the bremsstrahlung correction, recent dispersive calculations are used. For the one-photon-irreducible contribution at the one-loop level (for the doubly virtual form factor), we use a vector-meson-dominance-inspired model while taking into account the eta-eta' mixing.