Mixing of the f₀ and a₀ scalar mesons in threshold photoproduction

We examine the photoproduction of the light scalar mesons f₀-a₀(980) with emphasis on isospin-violating f₀ and a₀ mixing due to the mass difference between neutral and charged kaons. General forms for the invariant amplitude for scalar meson photoproduction are derived, which yield expressions for the invariant mass distribution of the final meson pairs. A final state interaction form factor is obtained which incorporates f₀ and a₀ mesons, KK̅ threshold effects, and f₀-a₀ mixing. This form factor is applied to predict the effective mass distribution of the ππ and KK̅ pairs in the vicinity of the KK̅ threshold. An estimate of the role of isospin mixing near threshold is provided. The potential role of polarized photons and protons is also discussed.