Using 4.48×108 ψ(3686) events collected with the BESIII detector, we search for the decays χcJ→μ+μ-J/ψ through the radiative decays ψ(3686)→γχcJ, where J=0, 1, 2. The decays χc1,2→μ+μ-J/ψ are observed, and the corresponding branching fractions are measured to be B(χc1→μ+μ-J/ψ)=(2.51±0.18±0.20)×10-4 and B(χc2→μ+μ-J/ψ)=(2.33±0.18±0.29)×10-4, where the first uncertainty is statistical and the second one systematic. No significant χc0→μ+μ-J/ψ decay is observed, and the upper limit on the branching fraction is determined to be 2.0×10-5 at 90% confidence level. Also, we present a study of dimuon invariant mass dependent transition form factor for the decays χc1,2→μ+μ-J/ψ.
Bibliographical noteFunding Information:
The BESIII collaboration thanks the staff of BEPCII and the IHEP computing center for their strong support. This work is supported in part by National Key Basic Research Program of China under Contract No. 2015CB856700; National Natural Science Foundation of China (NSFC) under Contracts No. 11847028, No. 11335008, No. 11425524, No. 11625523, No. 11635010, No. 11735014, No. 11505034, No. 11521505, No. 11575198, and No. U1732105; the Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; the CAS Center for Excellence in Particle Physics (CCEPP); Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contracts No. U1532257, No. U1532258, No. U1732263; CAS Key Research Program of Frontier Sciences under Contracts No. QYZDJ-SSW-SLH003, No. QYZDJ-SSW-SLH040; 100 Talents Program of CAS; INPAC and Shanghai Key Laboratory for Particle Physics and Cosmology; Foundation of Henan Educational Committee (No. 19A140015); Nanhu Scholars Program for Young Scholars of Xinyang Normal University; German Research Foundation DFG under Contract No. Collaborative Research Center CRC 1044; Istituto Nazionale di Fisica Nucleare, Italy; Koninklijke Nederlandse Akademie van Wetenschappen (KNAW) under Contract No. 530-4CDP03; Ministry of Development of Turkey under Contract No. DPT2006K-120470; National Science and Technology fund; The Swedish Research Council; U.S. Department of Energy under Contracts No. DE-FG02-05ER41374, No. DE-SC-0010118, No. DE-SC-0010504, No. DE-SC-0012069; University of Groningen (RuG) and the Helmholtzzentrum fuer Schwerionenforschung GmbH (GSI), Darmstadt.
© 2019 authors. Published by the American Physical Society.