Light meson spectroscopy from Dalitz plot analyses of η꜀ decays to η′K⁺K⁻, η′π⁺π⁻, and ηπ⁺π⁻ produced in two-photon interactions

Abstract

We study the processes γγ → η꜀ → η′K⁺K⁻, η′π⁺π⁻, and ηπ⁺π⁻ using a data sample of 519 fb⁻¹ recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e⁺e⁻ collider at center-of-mass energies at and near the Υ(nS) (n=2, 3, 4) resonances. This is the first observation of the decay η꜀ → η′K⁺K⁻ and we measure the branching fraction Γ(η꜀ → η′K⁺K⁻)/(Γ(η꜀ → η′π⁺π⁻) = 0.644 ± 0.039_(stat) ± 0.032_(sys). Significant interference is observed between γγ → ꜀ → ηπ⁺π⁻ and the nonresonant two-photon process γγ → ηπ⁺π⁻. A Dalitz plot analysis is performed of η꜀ decays to η′K⁺K⁻, η′π⁺π⁻, and ηπ⁺π⁻. Combined with our previous analysis of η꜀ → KK̅π, we measure the K₀^∗ (1430) parameters and the ratio between its η′K and πK couplings. The decay η꜀ → η′π⁺π⁻ is dominated by η꜀ → ηπ⁺π⁻ channel. We also compare η꜀ decays to η and η′ final states in association with scalar mesons as they relate to the identification of the scalar glueball.

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