Probing QCD with heavy quarkonia

Abstract

The sensitivity of the charmonium and bottomonium spectroscopy to the short distance part of the interquark potential is critically re-examined using the latest data. We confirm that the data cannot accomodate a QCD scale parameter\(\left( {\Lambda _{\overline {MS} } } \right)\) smaller than about 150 MeV, whereas we find no constraint on larger values for the scale parameter, contrary to a previous analysis. The effect of dynamical heavy quark masses in the loop correction to the perturbative potential is studied in detail and the effective four quark theory with a massive charmed quark is found to give an accurate description of the perturbative potential for quarkonia of mass up to about 200 GeV. It is argued that the experimental determination of the mass ande+e− decay width of the 1S and 2S toponium resonances (of mass round 80 GeV) with the accuracy anticipated at the forthcominge+e− colliders should enable the QCD scale parameter to be determined to within ±100 MeV.