Hello. When you have a plot of the cross section in function of the centre of mass energy of an e+e- -> hadrons collision, you get a graph with a few peaks which are due to the resonances (ρ, ω, J/ψ...). But I don't understand why at a resonance, the cross section goes up? Or other way around: why does the cross section drop between the resonances even though there is still hadronisation? Same for when you take the ratio R= σ(e-e+ -> hadrons)/σ(e-e+ -> μ-μ+) If you graph this, you get high R peaks for the resonances, but between the peaks, R stays horizontal for increasing s? Why? I hope my question is clear? I couldn't find a clear graphic that could show my problem.