ηc Hadroproduction at Large Hadron Collider Challenges NRQCD Factorization

We report on our analysis [1] of prompt eta(c) meson production, measured by the LHCb Collaboration at the Large Hadron Collider, within the framework of non-relativistic QCD (NRQCD) factorization up to the sub-leading order in both the QCD coupling constant alpha(s) and the relative velocity upsilon of the bound heavy quarks. We thereby convert various sets of J/psi and X-c,X-J long-distance matrix elements (LDMEs), determined by different groups in J/psi and X-c,X-J yield and polarization fits, to eta(c) and h(c) production LDMEs making use of the NRQCD heavy quark spin symmetry. The resulting predictions for eta(c) hadroproduction in all cases greatly overshoot the LHCb data, while the color-singlet model contributions alone would indeed be sufficient. We investigate the consequences for the universality of the LDMEs, and show how the observed tensions remain in follow-up works by other groups.