ηc Hadroproduction at Large Hadron Collider Challenges NRQCD Factorization
II. Institut für Theoretische Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
Published online: 22 March 2017
We report on our analysis  of prompt ηc 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 αs and the relative velocity v of the bound heavy quarks. We thereby convert various sets of J/ψ and χc,J long-distance matrix elements (LDMEs), determined by different groups in J/ψ and χc,J yield and polarization fits, to ηc and hc production LDMEs making use of the NRQCD heavy quark spin symmetry. The resulting predictions for ηc 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.
© The Authors, published by EDP Sciences, 2017
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