Abstract
The Upsilon (1S) meson production and polarization at high energies is studied in the framework of the k_T-factorization approach. Our consideration is based on the non-relativistic QCD formalism for a bound states formation and off-shell production amplitudes for hard partonic subprocesses. The direct production mechanism, feed-down contributions from radiative chi _b(mP) decays and contributions from Upsilon (3S) and Upsilon (2S) decays are taken into account. The transverse momentum dependent (TMD) gluon densities in a proton were derived from the Ciafaloni–Catani–Fiorani–Marchesini evolution equation and the Kimber-Martin–Ryskin prescription. Treating the non-perturbative color octet transitions in terms of multipole radiation theory, we extract the corresponding non-perturbative matrix elements for Upsilon (1S) and chi _b(1P) mesons from a combined fit to transverse momenta distributions measured at various LHC experiments. Then we apply the extracted values to investigate the polarization parameters lambda _theta , lambda _phi and lambda _{theta phi }, which determine the Upsilon (1S) spin density matrix. Our predictions have a reasonably good agreement with the currently available Tevatron and LHC data within the theoretical and experimental uncertainties.
Highlights
Our present work continues the line started in the previous studies [25,26]
We present a systematic analysis of the CMS [27,28,29], ATLAS [30] and LHCb [31–3√4] data on the Υ(1S) and χb(1P) production collected at s = 7, 8 and 13 TeV and we extract from these data non-perturbative matrix elements (NMEs) for the Υ(1S) and χb(1P) mesons
This ratio is sensitive to the color singlet (CS) and color octet (CO) production mechanisms and provides information complementary to the study of the S-wave bottomonium states
Summary
Our present work continues the line started in the previous studies [25,26]. We have considered there the inclusive production of Υ(3S), Υ(2S), χb(3P) and χb(2P) mesons and come to Υ(1S) and χb(1P) mesons. We have included in the fitting procedure the Υ(1S) transverse momentum distributions measur√ed by the CMS [27,28] and ATLAS [30] Collaborations at s = 7 and 13 TeV. Note that here we considered the color singlet wave functions of χb(1P) mesons as independent (not necessarily identical) free parameters, as it was proposed [64] to describe the LHC data on relative σ (χc2)/σ (χc1) production rate.
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