Comparative study of the scalar- and tensor-meson production in the reaction γγ^* (Q²)→ ηπ⁰

The cross section for the reaction γγ^* (Q²)→ ηπ⁰ was predicted on the basis of a simultaneous analysis of data from the Belle detector (Japan) on the reaction γγ → ηπ⁰ and data the KLOE detector (Italy) on the decay process ϕ → ηπ⁰γ. The production of a₀(980) scalar and a₂(1320) tensor mesons was studied in detail. It is shown that the QCD-predicted asymptotic behavior of the cross section for the process γ^*(Q²)γ → a₂(1320) → ηπ⁰ can be reproduced only upon taking into account the compensation of the contributions of ρ(770) and ω(782) mesons in the leading order by the contributions of their radial excitations in the Q² channel. It is expected that, at large Q², the cross section is dominated by the a₂(1320) contribution, but that, at Q² = 0, the a₂(1320) contribution is commensurate with the scalarmeson contribution.