TEVATRON-HERA Colour-Octet Charmonium Anomaly Versus Higher-Order QCD Effects

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Abstract
Approximately taking into account the higher-order effects due to multiple-gluon initial-state radiation, we extract from the latest Tevatron data of prompt J/psi hadroproduction the leading colour-octet matrix elements within the nonrelativistic-QCD (NRQCD) factorization formalism proposed by Bodwin, Braaten, and Lepage. We find that the matrix elements which describe the formation of J/psi mesons from colour-octet cc-bar pairs in the angular-momentum states ^{2S+1}L_J = ^1S_0 and ^3P_J, with J = 0,1,2, which are responsible for the excess of the predicted cross section of inelastic J/psi photoproduction over the existing HERA data at high values of the inelasticity variable z, are significantly reduced. We conclude that it is premature to proclaim a discrepancy between the Tevatron and HERA measurements of inclusive J/psi production in the NRQCD framework. We also consider J/psi mesons originating from the radiative feed down of promptly produced chi_{cJ} mesons.

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