Observation of $\chi_{c2}\to\eta'\eta'$ and $\chi_{c0,2}\to\eta\eta'$

Abstract

Using a sample of 447.9×106ψ(3686) events collected with the BESIII detector in 2009 and 2012, we study the decays χc0,2→ η′η′ and ηη′. The decays χc2→η′η′, χc0→ηη′, and χc2→ηη′ are observed for the first time with statistical significances of 9.6σ, 13.4σ, and 7.5σ respectively. The branching fractions are determined to be B(χc0→η′η′)=(2.19±0.03±0.14)×10−3, B(χc2→η′η′)=(4.76±0.56±0.38)×10−5, B(χc0→ηη′)=(8.92±0.84±0.65)×10−5, B(χc2→ηη′)=(2.27±0.43±0.25)×10−5, where the first uncertainties are statistical and the second systematic. The precision for the measurement of B(χc0→η′η′) is significantly improved compared to previous measurements. Based on the measured branching fractions, the role played by the doubly and singly Okubo-Zweig-Iizuka disconnected transition amplitudes for χc0,2 decays into pseudoscalar meson pairs can be clarified.