Evidence of ϒ(1S) -> J/ψ + χc1 and search for double-charmonium production in ϒ(1S) and ϒ(2S) decays
Abstract
Using data samples of 102 x 106 ϒð1SÞ and 158 x 106 ϒð2SÞ events collected with the Belle detector, a first experimental search has been made for double-charmonium production in the exclusive decays ϒð1S; 2SÞ RIGHTWARDS ARROW J=ψðψ0Þ þ X, where X 1/4 ηc, χcJðJ 1/4 0; 1; 2Þ, ηcð2SÞ, Xð3940Þ, and Xð4160Þ. No significant signal is observed in the spectra of the mass recoiling against the reconstructed J=ψ or ψ0 except for the evidence of χc1 production with a significance of 4.6σ for ϒð1SÞ RIGHTWARDS ARROW J=ψ þ χc1.
The measured branching fraction Bðϒð1SÞ RIGHTWARDS ARROW J=ψ þ χc1 Þ is 1/23.90 1.21ðstatÞ 0.23ðsystÞ x 10MINUS SIGN 6. The 90% C.L. upper limits on the branching fractions of the other modes having a significance of less than 3σ are determined.
These results are consistent with theoretical calculations using the nonrelativistic QCD factorization approach.