Bottomonia production and polarization in the NRQCD with kt-factorization. I: Υ(3S) and χb(3P) mesonsстатья
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Дата последнего поиска статьи во внешних источниках: 11 ноября 2019 г.
Аннотация:The Υ(3S) production and polarization at high energies is studied in the framework of kT-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 χb(3P) decays, we extract the corresponding non-perturbative matrix elements for Υ(3S) and χb(3P) mesons from a combined fit to Υ(3S) transverse momenta distributions measured by the CMS and ATLAS Collaborations at the LHC energies s√=7 and 13 TeV and central rapidities. Then we apply the extracted values to describe the CDF and LHCb data on Υ(3S) production and to investigate the polarization parameters λθ, λϕ and λθϕ, which determine the Υ(3S) spin density matrix. Our predictions have a good agreement with the currently available data within the theoretical and experimental uncertainties.