Measurement of the $\gamma^{\star}\gamma^{\star} \to \eta'$ transition form factor

We study the process e+e-→e+e-η′ in the double-tag mode and measure for the first time the γ⋆γ⋆→η′ transition form factor Fη′(Q12,Q22) in the momentum-transfer range 2center-of-mass energies near 10.6 GeV.