Abstract
We report on our analysis [1] 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.
Highlights
Despite great efforts from both experimental and theoretical sides ever since the J/ψ meson was discovered in 1974, the genuine mechanism describing the production of heavy quarkonium states, i.e. heavy quark-antiquark pairs QQ = cc, bb, has remained mysterious
We report on our analysis [1] of prompt ηc meson production, measured by the LHCb Collaboration at the Large Hadron Collider, within the framework of nonrelativistic 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 investigate the consequences for the universality of the long-distance matrix elements (LDMEs), and show how the observed tensions remain in follow-up works by other groups
Summary
The non-relativistic QCD (NRQCD) factorization formalism [2], which is built on the non-relativistic field theory [3], is arguably the most probable candidate theory in town. In this approach the production of heavy quarkonium factorizes into short-distance coefficients (SDCs), which are process dependent and can be calculated perturbatively as expansions of the QCD coupling constant αs, and long-distance matrix elements (LDMEs), which are supposed to be universal, and can be obtained through fitting to experimental data. It is of great interest to do a fully-fledged NRQCD analysis of prompt ηc production at NLO in αs and subleading order in v2
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