The 3γ decay of positronium (the bound state of e+e−) has a width that in QED is predicted to be Γ(3γ) = 2(π2 − 9)α6mec2/9π, where α is the fine structure constant.
(a) If the hadronic decay of the c c bound state J/ψ (3,100) proceeds via an analogous mechanism, but involving three gluons, use the experimental hadronic width (fragmentation into hadrons occurring with probability unity) Γ(3g) = 80 keV to estimate the effective strong interaction coupling constant αs.
(b) Determine αs from the radiative width Γ(ggγ) = 0.16 keV of the b b bound state γ (9,460)
