Bottomonia production and polarization in the NRQCD with kt-factorization. II: Upsilon (2S) and chib (2P) mesonsстатья
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Дата последнего поиска статьи во внешних источниках: 7 июля 2020 г.
Аннотация:The Y(2S) 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 direct production mechanism, feed-down contributions from radiative chib(3P) and chib(2P) decays and contributions from Y(3S) decays are taken into account. The transverse momentum dependent gluon densities in a proton were derived from the Ciafaloni–Catani–Fiorani–Marchesini evolution equation, Kimber-Martin-Ryskin prescription and Parton Branching method. Treating the non-perturbative color octet transitions in terms of the mulitpole radiation theory, we extract the corresponding non-perturbative matrix elements for Y(2S) and chib(2P) mesons from a combined fit to Y(2S) transverse momenta distributions measured by the CMS and ATLAS Collaborations at the LHC energies 7 and 13 TeV and from the relative production rate measured by the LHCb Collaboration at 7 and 8 TeV. Then we apply the extracted values to investigate the polarization parameters, which determine the Y(2S) spin density matrix. Our predictions have a good agreement with the currently available data within the theoretical and experimental uncertainties.