J/ψ and ψ′ total cross sections and formation times from data for charmonium suppression in pA collisions

Abstract The recent data for E866 on the x F dependence for charmonium suppression in pA collisions at 800 GeV are analyzed using a time- and energy-dependent preformed charmonium absorption cross section. For charmonium-nucleon c.m. energy 10 GeV the initially produced premeson has an absorption cross section of σ pr ≃3 mb. At the same energy but for the developed charmonium states one deduces for the total cross sections σ tot J / ψN =(2.8±0.3) mb, σ tot ψ ′ N =(10.5±3.6) mb. The date are compatible with a formation time τ 1/2 =0.6 fm/ c in the rest frame of the charmonium.