Two-loop Correction to the Leptonic Decay of Quarkonium


Applying asymptotic expansions at threshold, we compute the two-loop QCD correction to the short-distance coefficient that governs the leptonic decay ψ → l+l− of a S-wave quarkonium state and discuss its impact on the relation between the quarkonium non-relativistic wave function at the origin and the quarkonium decay constant in full QCD. PACS Nos.: 13.20… (More)


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