The $$\eta $$ η transition form factor from space- and time-like experimental data

The [Formula: see text] transition form factor is analyzed for the first time in both space- and time-like regions at low and intermediate energies in a model-independent approach through the use of rational approximants. The [Formula: see text] experimental data provided by the A2 Collaboration in the very low-energy region of the dielectron invariant mass distribution allows for the extraction of the most precise up-to-date slope and curvature parameters of the form factors as well as their values at zero and infinity. The impact of these new results on the mixing parameters of the [Formula: see text]-[Formula: see text] system, together with the role played by renormalization dependent effects, and on the determination of the [Formula: see text] couplings from [Formula: see text] and [Formula: see text] radiative decays is also discussed.