Reconciling J/psi production at HERA, RHIC, Tevatron, and LHC with NRQCD factorization at next-to-leading order

TL;DR

This paper performs a comprehensive NLO calculation of J/psi production within NRQCD, fitting experimental data from multiple colliders to validate the factorization approach and highlight the importance of color-octet processes.

Contribution

It provides the first rigorous NLO test of NRQCD factorization across different collider experiments with a combined fit of color-octet matrix elements.

Findings

Successful description of p_T distributions at Tevatron, HERA, RHIC, and LHC

Color-octet processes are essential in all experimental fits

First NLO validation of NRQCD factorization across multiple experiments

Abstract

We calculate the cross section of inclusive direct J/psi hadroproduction at next-to-leading order (NLO) within the factorization formalism of nonrelativistic quantum chromodynamics (NRQCD), including the full relativistic corrections due to the intermediate 1S_0^[8], 3S_1^[8], and 3P_J^[8] color-octet states. We perform a combined fit of the color-octet (CO) long-distance matrix elements to the transverse-momentum (p_T) distributions measured by CDF at the Fermilab Tevatron and H1 at DESY HERA and demonstrate that they also successfully describe the p_T distributions from PHENIX at BNL RHIC and CMS at the CERN LHC as well as the photon-proton c.m. energy and (with worse agreement) the inelasticity distributions from H1. This provides a first rigorous test of NRQCD factorization at NLO. In all experiments, the CO processes are shown to be indispensable.