arXiv : Observation of $\chi_{c2}\to\eta'\eta'$ and $\chi_{c0,2}\to\eta\eta'$
arXiv : Observation of $\chi_{c2}\to\eta'\eta'$ and $\chi_{c0,2}\to\eta\eta'$
Using a sample of 448.1×106 ψ(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 …