DECAYS ETA(C)-]GAMMA-GAMMA ETA(B)-]GAMMA-GAMMA - A TEST FOR POTENTIAL MODELS

We use a simple perturbation theory argument and measurements of charmonium leptonic widths Γ(ψNS→e+e-) to estimate the ratio R0Ψηc1S(0)2/Ψψ1S(0)2 in the general context of nonrelativistic potential models. We obtain R0=1.4±0.1. We then apply well known potential model formulas, which include lowest order QCD corrections, to find Γ(ηc→γγ)/Γ(ψ1S→e+e-)2.2±0.2. The central value for Γ(ψ1S→e+e-) in the 1992 Particle Data Group Tables then leads to a (nonrelativistic) prediction Γ(ηc→γγ)>11.8±0.8 keV. This prediction is in good agreement with a recent measurement by the ARGUS Collaboration, is consistent with a recent measurement by the L3 Collaboration, but is significantly higher than several other measurements and previous theoretical estimates, which usually assume R0=1. The correction to R0=1 is estimated to be smaller but non-negligible for the bb̄ system. Using the current central measurement for Γ(Υ1S→e+e-) we find Γ(ηb→γγ)>0.58±0.03 keV. A rough estimate of relativistic corrections reduces the expected two photon rates to about 8.8 and 0.52 keV for the ηc and ηb mesons, respectively. Such corrections, however, are not expected to significantly affect our estimates of R0. An estimate of Γ(ηc(2S)→γγ) is given as well. © 1995 The American Physical Society.