https://doi.org/10.1140/epjc/s10052-019-6968-0
Letter
NRQCD colour-octet expansion vs. LHC quarkonium production: signs of a hierarchy puzzle?
1
LIP, Lisbon, Portugal
2
CERN, Geneva, Switzerland
* e-mail: Pietro.Faccioli@cern.ch
** e-mail: carlos.lourenco@cern.ch
Received:
27
April
2019
Accepted:
20
May
2019
Published online:
30
May
2019
The observation of unpolarized quarkonium production in high energy pp collisions, at mid rapidity, implies a significant violation of the non-relativistic QCD (NRQCD) velocity scaling rules. A precise experimental confirmation of this picture could definitely rule out the current formulation of the factorization expansion. This conclusion relies on current perturbative determinations of the short-distance kinematic factors and may be reverted if improved calculations would modify, in a very specific way, their transverse momentum dependences. That solution would result, however, in a full degeneracy in the presently assumed basis of 
Fock states. Therefore, whatever the outcome, improved polarization measurements will challenge and improve our fundamental understanding of quarkonium production.
© The Author(s), 2019
