Leptonic widths of high excitations in heavy quarkonia

Agreement with the measured electronic widths of the resonances ψ(4040), ψ(4415) and ϒ(11 019) is shown to be obtained if two effects are taken into account: (i) a flattening of the confining potential at distances r ⪆ 1.2 fm, which gives a drop in the leptonic widths of high excitations of about 10–20%, but does not affect low-lying states, and (ii) switching off the gluon-exchange (GE) interaction for those nS states which have a rms radius r n ⪆ 1.4 fm. We also show that an exponential type of screening of the GE interaction barely changes the leptonic widths, Γ( nS ), for n ⩽ 5. The leptonic widths of and Γ(ψ(5 S )) ≈ 0.54 keV are predicted.