Heavy-quarkonium theory in the LHC era

Abstract

We report on recent progress in testing the factorization fo rmalism of nonrelativistic quantum chromodynamics (NRQCD) at next-to-leading order (NLO) for J/ψ yield and polarization. We demonstrate that it is possible to unambiguously determine the leading color-octet long-distance matrix elements (LDMEs) in compliance with the velocity scaling rules through a global fit to experimental data of unpolarized J/ψ production in pp, pp, ep, γγ, and e + e − collisions. Three data sets not included in the fit, from hadroproduction and from ph otoproduction in the fixed-target and colliding-beam modes, are nicely reproduced. The polarization observables measured in different frames at DESY HERA and CERN LHC reasonably agree with NLO NRQ CD predictions obtained using the LDMEs extracted from the global fit, while me asurements at the FNAL Tevatron exhibit severe disagreement. We demonstrate that alternat ive LDME sets recently obtained, with different philosophies, in two other NLO NRQCD analyses of J/ψ yield and polarization also fail to reconcile the Tevatron polarization data with the ot her available world data.