QCD radiative corrections to χcJ production at hadron colliders
Ma, Yan-Qing · Wang, Kai · Chao, Kuang-Ta
Original · EN
To clarify the outstanding problem in charmonium production that existing theories cannot explain the observed cross sections of χcJ (J=0,1,2) and ratio Rᵪc=σᵪc₂/σᵪc₁≈ 0.75 (in contrast to the spin counting value 5/3) at the Tevatron, we study the complete next-to-leading order radiative corrections in nonrelativistic QCD, and find next-to-leading order contributions of ³Pⱼ[¹] are more important than leading order at high pₜ, and ³P₁[¹] decreases slower than ³P₂[¹], implying a natural explanation for the Rᵪc puzzle. By fitting Rᵪc, the predicted cross sections of χcJ are found to agree with data. The result indicates color-octet contribution is crucially needed, thus providing a unique test for heavy quarkonium production mechanisms. Feed-down contributions of χcJ to prompt J/ψ production are estimated to be substantial, about 30-40% at pₜ=20 GeV. Production of χcJ (J=0,1,2) at the LHC is also predicted.
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