Inclusive radiative J/ψ decays

Journal article

Using data taken with the CLEO-c detector at the Cornell Electron Storage Ring, we have investigated the direct-photon momentum spectrum in the decay J/ψ(1S)→γgg, via the "tagged" process: e+e-→ψ(2S); ψ(2S)→J/ψπ+π-; J/ψ→γ+X. Including contributions from two-body radiative decay processes, we find the ratio of the inclusive direct-photon branching fraction to that of the dominant three-gluon branching fraction [Rγ=B(ggγ)/B(ggg)] to be Rγ=0.137±0.001±0.016±0.004, where the errors shown are statistical, systematic, and the model-dependent uncertainty related to the extrapolation to zero photon energy. The shape of the scaled photon energy spectrum in J/ψ→ggγ is observed to be very similar to that of Υ→ggγ. The Rγ value obtained is roughly consistent with that expected by a simple quark-charge scaling [Rγ∼(qc/qb)2] of the value determined at the Υ(1S), but somewhat higher than the value expected from the running of the strong coupling constant. © 2008 The American Physical Society.

Authors: Besson, D; Pedlar, T; Cronin-Hennessy, D; Gao, K; Hietala, J

• Journal: Physical Review D
• Volume: 78
• Issue: 3
• Publication date: 2008-08-19
• DOI: 10.1103/PhysRevD.78.032012
• EISSN: 1550-2368
• ISSN: 1550-7998
• Language: English