Observation of the charmonium decay η_c→γγ in J/ψ→γη_c

2024/12/17 by BESIII Collaboration, Ablikim, M., Achasov, M. N. +662 · 1 citation
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex)

paper · doi:10.48550/arxiv.2412.12998

Abstract

Using (2712.4±14.3)×10⁶ ψ(3686) events collected with the BESIII detector at the BEPCII collider, the decay η_c→γγ in J/ψ→γη_c is observed. We determine the product branching fraction B(J/ψ→γη_c)\timesB(η_c→γγ)=(5.23±0.26_\rmstat.±0.30_\rmsyst.)×10^-6. This result is consistent with the LQCD calculation (5.34±0.16)×10^-6 from HPQCD in 2023. By using the world-average values of B(J/ψ→γη_c) and the total decay width of η_c, the partial decay width Γ(η_c→γγ) is determined to be (11.30±0.56_\rmstat.±0.66_\rmsyst.±1.14_\rmref.)~\rmkeV, which deviates from the corresponding world-average value by 3.4σ.

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