Abstract
The Upsilon (3S) production and polarization at high energies is studied in the framework of k_T-factorization approach. Our consideration is based on the non-relativistic QCD formalism for bound states formation and off-shell production amplitudes for hard partonic subprocesses. The transverse momentum dependent (TMD, or unintegrated) gluon densities in a proton were derived from the Ciafaloni-Catani-Fiorani-Marchesini (CCFM) evolution equation as well as from the Kimber–Martin–Ryskin (KMR) prescription. Treating the non-perturbative color octet transitions in terms of the multipole radiation theory and taking into account feed-down contributions from radiative chi _b(3P) decays, we extract the corresponding non-perturbative matrix elements for Upsilon (3S) and chi _b(3P) mesons from a combined fit to Upsilon (3S) transverse momenta distributions measured by the CMS and ATLAS Collaborations at the LHC energies sqrt{s} = 7 and 13 TeV and central rapidities. Then we apply the extracted values to describe the CDF and LHCb data on Upsilon (3S) production and to investigate the polarization parameters lambda _theta , lambda _phi and lambda _{theta phi }, which determine the Upsilon (3S) spin density matrix. Our predictions have a good agreement with the currently available data within the theoretical and experimental uncertainties.
Highlights
Fock state 2S+1L (a) J with spinS, orbital angular momentum L, total angular momentum J and color representation a from long-distance non-perturbative matrix elements (NMEs), which describe the transition of that intermediate Q Qstate into a physical quarkonium via soft gluon radiation.The NMEs are assumed to be universal, not dependent on the quarkonium momentum and obeying certain hierarchy in powers of the relative heavy quark velocity vQ ∼ log−1 m Q/ QCD with m Q being the heavy quark mass
We have considered the Υ(3S) production at the Tevatron and LHC in the framework of kT -factorization approach
Our consideration was based on the off-shell production amplitudes for hard partonic subprocesses, non-relativistic QCD (NRQCD) formalism for the formation of bound states and TMD gluon densities in a proton
Summary
S, orbital angular momentum L, total angular momentum J and color representation a from long-distance non-perturbative matrix elements (NMEs), which describe the transition of that intermediate Q Qstate into a physical quarkonium via soft gluon radiation. The fits involving low- pT data result in the conclusion that the ψ and J/ψ production at large transverse momenta is dominated by color-octet 3 S1(8) contributions with strong transverse polarization, that contradicts to the unpolarized production seen at the Tevatron and LHC. A possible solution to the problem above has been proposed recently [21] in the framework of a model that interprets the soft final state gluon radiation (which transforms an unbound Q Qpair into a physical quarkonium state) as a series of color-electric dipole transitions In this way the NMEs are represented in an explicit form inspired by the classical multipole radiation theory, that has dramatic consequences for the polarization of the final state mesons since the spin structure of the transition amplitudes is specified.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
