Observation of $\ddot{I}{‡}_{c1}$ decays into vector meson pairs $\ddot{I}•\ddot{I}•$, $\ddot{I}‰\ddot{I}‰$, and $\ddot{I}‰\ddot{I}•$

Abstract

Decays of $\ddot{I}{‡}_{c1}$ to vector meson pairs $\ddot{I}•\ddot{I}•$, $\ddot{I}‰\ddot{I}‰$ and $\ddot{I}‰\ddot{I}•$ are observed for the first time using $(106\pm 4)\times 10^6$ $\psip$ events accumulated at the BESIII detector at the BEPCII $e^{+}{e}^{-}$ collider. The branching fractions are measured to be $(4.4\pm 0.3\pm 0.5)\times 10^{-4}$, $(6.0\pm 0.3\pm 0.7)\times 10^{-4}$, and $(2.2\pm 0.6\pm 0.2)\times 10^{-5}$, for $\ddot{I}{‡}_{c1}\to \ddot{I}•\ddot{I}•$, $\ddot{I}‰\ddot{I}‰$, and $\ddot{I}‰\ddot{I}•$, respectively. The observation of $\ddot{I}{‡}_{c1}$ decays into a pair of vector mesons $\ddot{I}•\ddot{I}•$, $\ddot{I}‰\ddot{I}‰$ and $\ddot{I}‰\ddot{I}•$ indicates that the hadron helicity selection rule is significantly violated in $\ddot{I}{‡}_{cJ}$ decays. In addition, the measurement of $\ddot{I}{‡}_{cJ}\to \ddot{I}‰\ddot{I}•$ gives the rate of doubly OZI-suppressed decay. Branching fractions for $\ddot{I}{‡}_{c0}$ and $\ddot{I}{‡}_{c2}$ decays into other vector meson pairs are also measured with improved precision.

4 pages, 2 figures