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Two-photon width of eta_c and eta'_c from Heavy-Quark Spin Symmetry

J. P. Lansberg·T. N. Pham
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Abstract

We evaluate the two-photon width of the pseudoscalar charmonia, Gamma(eta_c -> gamma gamma) and Gamma(eta'_c -> gamma gamma), within a Heavy-Quark Spin-Symmetry setting and show that whereas the former agrees with experiment, the latter is more than twice larger than the recent measurement by CLEO. When binding-energy effects are included in the eta'_c case, the discrepancy is worse, pointing out at a possible anomaly in the eta'_c decay.

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J. P. Lansberg, T. N. Pham. 2006-07-13. Two-photon width of eta_c and eta'_c from Heavy-Quark Spin Symmetry. https://doi.org/10.1103/physrevd.74.034001

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