Abstract
The LHC quarkonium production data reveal a startling observation: the J/ψ, ψ(2S), χc1, χc2 and ϒ(nS)pT-differential cross sections in the central rapidity region are compatible with one universal momentum scaling pattern. Considering also the absence of strong polarizations of directly and indirectly produced S-wave mesons, we conclude that there is currently no evidence of a dependence of the partonic production mechanisms on the quantum numbers and mass of the final state. The experimental observations supporting this universal production scenario are remarkably significant, as shown by a new analysis approach, unbiased by specific theoretical calculations of partonic cross sections, which are only considered a posteriori, in comparisons with the data-driven results.
Highlights
The LHC quarkonium production measurements reveal a startling observation: the J/ψ, ψ(2S), χc1,2 and Υ(nS) pT-differential cross sections are compatible with one universal momentum scaling pattern
In a previous publication [2], we showed how easy it is to create puzzles when conducting global fits of quarkonium production data in the framework of non-relativistic quantum chromodynamics (NRQCD)
We describe the details of our original data-fitting approach, where the individual physical contributions to quarkonium production are exclusively discriminated by their characteristic polarizations, while the pT distributions and relative normalizations are parametrized by a flexible, empirical function
Summary
When presented as pT/M distributions, where M is the mass of the quarkonium state, the prompt J/ψ, χc, χc2, ψ(2S) and Υ(nS) production cross sections are all compatible with a single kinematic dependence, at least for mid-rapidity (|y| 1) and for not-too-small pT/M. This observation confirms, with higherpT data, a trend first noticed in Ref. The kinematic dependence of the partonic cross section of a given process is invariant by simultaneous rescaling of all energy-related variables This translates to an invariance by pT/M rescaling, if the longitudinal momentum components can be neglected: such scaling is not expected to be valid in the low pT/M and high-rapidity region of the LHCb data We discuss how the current models of quarkonium production relate to this observation
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