Helicity amplitude analysis of χ cJ → ϕϕ

Using (447.9 ± 2.3) million ψ(3686) events collected with the BESIII detector, the decays of χ cJ → ϕϕ (J = 0, 1, 2) have been studied via the decay ψ(3686) → γχ cJ . The branching fractions of the decays χ cJ → ϕϕ (J = 0, 1, 2) are determined to be (8.59 ± 0.27 ± 0.20) × 10 −4, (4.26 ± 0.13 ± 0.15) × 10 −4, and (12.67 ± 0.28 ± 0.33) × 10 −4, respectively, which are the most precise measurements to date. From a helicity amplitude analysis of the process ψ(3686) → γχ cJ , χ cJ → ϕϕ, ϕ → K + K − , the polarization parameters of the χ cJ → ϕϕ decays are determined for the first time.