Upsilonium polarization as a touchstone in understanding the proton dynamics in QCD

In the framework of the k_t-factorization approach, the production of $Upsilon mesons at the Fermilab Tevatron and CERN LHC is considered, and the predictions on the spin alignment parameter $alpha$ are presented. We argue that measuring the polarization of quarkonium states can serve as a crucial test discriminating two competing theoretical approaches to parton dynamics in QCD.