ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2011, vol. 107, p. -
Observation of χc1 decays into Vector Meson Pairs ÏÏ, ωω, and ωï
Using (106±4)×106 ψ(3686) events accumulated with the BESIII detector at the BEPCII e+e- collider, we present the first measurement of decays of χc1 to vector meson pairs ÏÏ, ωω, and ωÏ. The branching fractions are measured to be (4.4±0.3±0.5)×10-4, (6.0±0.3±0.7)×10-4, and (2.2±0.6±0. 2)×10-5, for χc1→Ï Ï, ωω, and ωÏ, respectively, which indicates that the hadron helicity selection rule is significantly violated in χcJ decays. In addition, the measurement of χcJ→ωÏ provides the first indication of the rate of doubly OZI-suppressed χcJ decay. Finally, we present improved measurements for the branching fractions of χc0 and χc2 to vector meson pairs. © 2011 American Physical Society.