Higher-Order Effects on Inelastic J/psi Photoproduction

TL;DR

This paper incorporates higher-order effects in inelastic J/psi photoproduction, leading to a revised extraction of color-octet matrix elements that reconcile Tevatron and HERA measurements within NRQCD.

Contribution

It introduces a method to account for higher-order effects in J/psi production, refining the extraction of nonperturbative matrix elements within NRQCD.

Findings

Reduced color-octet matrix elements for J/psi formation.

Reconciliation of Tevatron and HERA J/psi production data.

Improved agreement between theory and experiment.

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. We find that the matrix elements which describe the formation of J/psi mesons from colour-octet c c-bar pairs in the angular-momentum states (2S+1)^L_J = 1^S_0 and 3^P_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. As a consequence, the Tevatron and HERA measurements of inclusive J/psi production are reconciled in the NRQCD framework.