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

We study the processes γ γ → η c → η ′ K + K - , η ′ π + π - , and η π + 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 ( n S ) ( n = 2 , 3, 4) resonances. This is the first observation of the decay η c → η ′ K + K - and we measure the branching fraction Γ ( η c → η ′ K + K - ) / ( Γ ( η c → η ′ π + π - ) = 0.644 ± 0.03 9 stat ± 0.03 2 sys . Significant interference is observed between γ γ → η c → η π + π - and the nonresonant two-photon process γ γ → η π + π - . A Dalitz plot analysis is performed of η c decays to η ′ K + K - , η ′ π + π - , and η π + π - . Combined with our previous analysis of η c → K K ¯ π , we measure the K 0 * ( 1430 ) parameters and the ratio between its η ′ K and π K couplings. The decay η c → η ′ π + π - is dominated by the f 0 ( 2100 ) resonance, also observed in J / ψ radiative decays. A new a 0 ( 1700 ) → η π resonance is observed in the η c → η π + π - channel. We also compare η c decays to η and η ′ final states in association with scalar mesons as they relate to the identification of the scalar glueball.