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arXiv · 1411.5287

$η_c$ production at the LHC challenges nonrelativistic-QCD factorization

Mathias Butenschoen·Zhi-Guo He·Bernd A. Kniehl
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Abstract

We analyze the first measurement of $η_c$ production, performed by the LHCb Collaboration, in the nonrelativistic-QCD (NRQCD) factorization framework at next-to-leading order (NLO) in the strong-coupling constant $α_s$ and the relative velocity $v$ of the bound quarks including the feeddown from $h_c$ mesons. Converting the long-distance matrix elements (LDMEs) extracted by various groups from $J/ψ$ yield and polarization data to the $η_c$ 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.

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Mathias Butenschoen, Zhi-Guo He, Bernd A. Kniehl. 2015-01-18. $η_c$ production at the LHC challenges nonrelativistic-QCD factorization. https://doi.org/10.1103/physrevlett.114.092004

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