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

Abstract

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.