We present an analysis of the process ψ(3686)→ω-ω¯+ (ω-→K-Λ, ω¯+→K+Λ¯, Λ→pπ-, Λ¯→p¯π+) based on a dataset of 448×106 ψ(3686) decays collected with the BESIII detector at the BEPCII electron-positron collider. The helicity amplitudes for the process ψ(3686)→ω-ω¯+ and the decay parameters of the subsequent decay ω-→K-Λ (ω¯+→K+Λ¯) are measured for the first time by a fit to the angular distribution of the complete decay chain, and the spin of the ω- is determined to be 3/2 for the first time since its discovery more than 50 years ago.
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The BESIII Collaboration thanks the staff of BEPCII and the IHEP computing center for their strong support. The authors thank Professor Zuotang Liang, Professor Yukun Song, Professor Xiaogang He, and Dr. Jusak Tandean for useful discussions. This work is supported in part by National Key Basic Research Program of China under Contract No. 2020YFA0406300; National Natural Science Foundation of China (NSFC) under Contracts No. 11625523, No. 11635010, No. 11735014, No. 11822506, No. 11835012, No. 11935015, No. 11935016, No. 11935018, and No. 11961141012; the Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contracts No. U1732263 and No. U1832207; CAS Key Research Program of Frontier Sciences under Contracts No. QYZDJ-SSW-SLH003 and No. QYZDJ-SSW-SLH040; 100 Talents Program of CAS; Institute of Nuclear and Particle Physics (INPAC) and Shanghai Key Laboratory for Particle Physics and Cosmology; ERC under Contract No. 758462; German Research Foundation DFG under Contracts No. 443159800, Collaborative Research Center CRC 1044, FOR 2359, and GRK 214; Istituto Nazionale di Fisica Nucleare, Italy; Ministry of Development of Turkey under Contract No. DPT2006K-120470; National Science and Technology fund; Olle Engkvist Foundation under Contract No. 200-0605; STFC (United Kingdom); The Knut and Alice Wallenberg Foundation (Sweden) under Contract No. 2016.0157; The Royal Society, United Kingdom under Contracts No. DH140054 and No. DH160214; The Swedish Research Council; and U.S. Department of Energy under Contracts No. DE-FG02-05ER41374 and No. DE-SC-0012069.
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