| Popis: |
Using 4.479 × 108 ψð3686Þ events collected with the BESIII detector, we search for the decays ψð3686Þ → eþe−χcJ and χcJ → eþe−J=ψ, where J ¼ 0, 1, 2. The decays ψð3686Þ → eþe−χcJ and χcJ → eþe−J=ψ are observed for the first time. The measured branching fractions are B(ψð3686Þ → eþe−χcJ) ¼ ð11.7 2.5 1.0Þ × 10−4, ð8.6 0.3 0.6Þ × 10−4, ð6.9 0.5 0.6Þ × 10−4 for J ¼ 0, 1, 2, and BðχcJ →eþe−J=ψÞ¼ð1.510.300.13Þ×10−4, ð3.730.090.25Þ×10−3, ð2.480.080.16Þ×10−3 for J ¼ 0, 1, 2, respectively. The ratios of the branching fractions B(ψð3686Þ → eþe−χcJ)=B(ψð3686Þ → γχcJ) and B(χcJ → eþe−J=ψ)=B(χcJ → γJ=ψ) are also reported. Also, the α values of helicity angular distributions of the eþe− pair are determined for ψð3686Þ → eþe−χc1;2 and χc1;2 → eþe−J=ψ. |
