Observation of e⁺e⁻ → ωχ_{c1, 2} near √s̅ = 4.42 and 4.6 GeV



Based on data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies √s̅ > 4.4 GeV, the processes e⁺e⁻ → ωχ(c1,2) are observed for the first time. With an integrated luminosity of 1074 pb⁻¹ near √s̅ = 4.42 GeV, a significant ωχ(c2) signal is found, and the cross section is measured to be (20.9 ± 3.2 ± 2.5) pb. With 567 pb⁻¹ near √s̅ = 4.6 GeV, a clear ωχ(c1) signal is seen, and the cross section is measured to be (9.5 ± 2.1 ± 1.3) pb, while evidence is found for an ωχ(c2) signal. The first errors are statistical, and the second are systematic. Due to low luminosity or low cross section at other energies, no significant signals are observed. In the ωχ(c2) cross section, an enhancement is seen around √s̅ = 4.42 GeV. Fitting the cross section with a coherent sum of the ψ(4415) Breit-Wigner function and a phase-space term, the branching fraction B(ψ(4415) → ωχ(c2)) is obtained to be of the order of 10⁻¹.



Luminescence, Branching fractions (Nuclear physics), Uncertainty, Phase space (Statistical physics), Leptonic decays, Photons, Atomic mass


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. 11125525, No. 11235011, No. 11322544, No. 11335008, No. 11425524; Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contracts No. 11179007, No. U1232201, No. U1332201; CAS under Contracts No. KJCX2-YW-N29, No. KJCX2-YW-N45; German Research Foundation DFG under Contract No. Collaborative Research Center CRC-1044; Ministry of Development of Turkey under Contract No. DPT2006K-120470; Russian Foundation for Basic Research under Contract No. 14-07-91152; U.S. Department of Energy under Contracts No. DE-FG02-04ER41291, No. DE-FG02-05ER41374, No. DE-FG02-94ER40823, No. DESC0010118; WCU Program of National Research Foundation of Korea under Contract No. R32-2008-000-10155-0.


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