ηc Production at the LHC Challenges Nonrelativistic QCD Factorization

We analyze the first measurement of eta(c) production, performed by the LHCb Collaboration, in the nonrelativistic QCD (NRQCD) factorization framework at next-to-leading order (NLO) in the strong-coupling constant alpha(s) and the relative velocity v of the bound quarks including the feeddown from h(c) mesons. Converting the long-distance matrix elements extracted by various groups from J/psi yield and polarization data to the eta(c) case using heavy-quark spin symmetry, we find that the resulting NLO NRQCD predictions greatly overshoot the LHCb data, while the color-singlet model provides an excellent description.