Observation of η′ → ωe⁺e⁻

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Abstract

Based on a sample of η′ mesons produced in the radiative decay J/ψ → γη′ in 1.31 x 10⁹ J/ψ events collected with the BESIII detector, the decay η′ → ωe⁺e⁻ is observed for the first time, with a statistical significance of 8σ. The branching fraction is measured to be ℬ(η′ → ωe⁺e⁻) = (1.97 ± 0.34(stat) ± 0.17(syst)) x 10⁻⁴, which is in agreement with theoretical predictions. The branching fraction of η′ → ωγ is also measured to be (2.55 ± 0.03(stat) ± 0.16(syst)) x 10⁻², which is the most precise measurement to date, and the relative branching fraction 𝓑(η′ → ωe⁺e⁻) / 𝓑(η′ → ωγ) is determined to be (7.71 ± 1.34(stat) ± 0.54(syst)) x 10⁻³.

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Keywords

Branching fractions (Nuclear physics), Atomic mass, Uncertainty, Photons, J/ψ (J/psi) meson

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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, and No. 11175189; Youth Science Foundation of China under Contract No. Y5118T005C; Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contracts No. 11179007, No. U1232201, and No. U1332201; CAS under Contracts No. KJCX2-YW-N29 and No. KJCX2-YW-N45; German Research Foundation DFG under Collaborative Research Center Contract No. 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, and No. DESC0010118; WCU Program of National Research Foundation of Korea under Contract No. R32-2008-000-10155-0.

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©2015 American Physical Society

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