Observation of ${\ensuremath{\chi}}_{c1}$ Decays into Vector Meson Pairs $\ensuremath{\phi}\ensuremath{\phi}$, $\ensuremath{\omega}\ensuremath{\omega}$, and $\ensuremath{\omega}\ensuremath{\phi}$

Observation of $χ_{c 1}$ Decays into Vector Meson Pairs $ϕ ϕ$ , $ω ω$ , and $ω ϕ$

M. Ablikim et al. (BESIII Collaboration)

Phys. Rev. Lett. 107, 092001 – Published 22 August 2011

Abstract

Using $(106 \pm 4) \times 10^{6}$ $ψ (3686)$ events accumulated with the BESIII detector at the BEPCII $e^{+} e^{-}$ collider, we present the first measurement of decays of $χ_{c 1}$ to vector meson pairs $ϕ ϕ$ , $ω ω$ , and $ω ϕ$ . The branching fractions are measured to be $(4.4 \pm 0.3 \pm 0.5) \times 10^{- 4}$ , $(6.0 \pm 0.3 \pm 0.7) \times 10^{- 4}$ , and $(2.2 \pm 0.6 \pm 0.2) \times 10^{- 5}$ , for $χ_{c 1} \to ϕ ϕ$ , $ω ω$ , and $ω ϕ$ , respectively, which indicates that the hadron helicity selection rule is significantly violated in $χ_{cJ}$ decays. In addition, the measurement of $χ_{cJ} \to ω ϕ$ provides the first indication of the rate of doubly OZI-suppressed $χ_{cJ}$ decay. Finally, we present improved measurements for the branching fractions of $χ_{c 0}$ and $χ_{c 2}$ to vector meson pairs.