Observation of $\chi_{c1}$ decays into vector meson pairs $\phi\phi$, $\omega\omega$, and $\omega\phi$

摘要

Decays of $\chi_{c1}$ to vector meson pairs $\phi\phi$, $\omega\omega$ and$\omega\phi$ are observed for the first time using $(106\pm4)\times 10^6$$\psip$ events accumulated at the BESIII detector at the BEPCII $e^+e^-$collider. The branching fractions are measured to be $(4.4\pm 0.3\pm 0.5)\times10^{-4}$, $(6.0\pm 0.3\pm 0.7)\times 10^{-4}$, and $(2.2\pm 0.6\pm 0.2)\times10^{-5}$, for $\chi_{c1}\to \phi\phi$, $\omega\omega$, and $\omega\phi$,respectively. The observation of $\chi_{c1}$ decays into a pair of vectormesons $\phi\phi$, $\omega\omega$ and $\omega\phi$ indicates that the hadronhelicity selection rule is significantly violated in $\chi_{cJ}$ decays. Inaddition, the measurement of $\chi_{cJ}\to \omega\phi$ gives the rate of doublyOZI-suppressed decay. Branching fractions for $\chi_{c0}$ and $\chi_{c2}$decays into other vector meson pairs are also measured with improved precision.