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HK: Fachverband Hadronen und Kerne
HK 35: Hadron Structure and Spectroscopy II
HK 35.4: Talk
Tuesday, March 17, 2009, 17:45–18:00, H-ZO 30
J/ψ→3γ as an ideal system to study high order QCD corrections — •Jorge Segovia, David R. Entem, and Francisco Fernandez — Universidad de Salamanca, E-37008 Salamanca, Spain
CLEO collaboration has recently measured the branching ratio of the J/ψ→3γ. A signal of 6σ significance was found with branching fraction B3γ=(1.2±0.3±0.2)×10−5 [1].
A thorough study of the 1– resonances in the constituent quark model has been done in Ref [2]. In this work not only the meson masses, but electromagnetic, leptonic and strong width decays are succesfully reproduced. Using the model wave function for the J/ψ we obtain B3γ=3.4×10−5, almost three times the experimental value.
One loop QCD corrections include five diagrams which take into account vertex, self-energy and ladder, corrections and can be casted in the form A(αs/π). Using the value of αs(mc) provided by the model, this correction almost cancel the zeroth order approximation giving a theoretical prediction compatible with zero. Two loop corrections are more involved to handle. We made a naive estimation of the contribution at order αs2 obtaining a theoretical value of B3γ=0.6×10−5.
Our result shows that the precise mesure of the J/ψ→3γ decay is very important to understand the role of the higher order QCD corrections although more theoretical work has to be done to obtain more accurate results.
[1] CLEO collaboration G. S. Adams et al, arXiv:0806.0671[hep-ex].
[2] J. Segovia, D. R. Entem, and F. Fernandez, accepted for publication in Phys. Rev. D.