Inclusive quarkonium production in pp collisions at √s = 5.02 TeV

Abstract

This article reports on the inclusive production cross section of several quarkonium states, $\textrm{J}/\psi$, $\psi \mathrm{(2S)}$, $\Upsilon \mathrm (1S)$, $\Upsilon \mathrm{(2S)}$, and $\Upsilon \mathrm{(3S)}$, measured with the ALICE detector at the LHC, in pp collisions at $\sqrt{s} = 5.02$ TeV. The analysis is performed in the dimuon decay channel at forward rapidity ($2.5< y < 4$). The integrated cross sections and transverse-momentum ($p_{\textrm{T}}$) and rapidity ($y$) differential cross sections for $\textrm{J}/\psi$, $\psi \mathrm{(2S)}$, $\Upsilon \mathrm (1S)$, and the $\psi \mathrm{(2S)}$-to-$\textrm{J}/\psi$ cross section ratios are presented. The integrated cross sections, assuming unpolarized quarkonia, are: $\sigma _{\textrm{J}/\psi }$ ($p_{\textrm{T}} <20$ GeV/c) = 5.88 ± 0.03 ± 0.34$~\mu$b, $\sigma _{\psi \mathrm{(2S)}}$ ($p_{\textrm{T}} <12$ GeV/c) = 0.87 ± 0.06 ± 0.10$~\mu$b, $\sigma _{\Upsilon \mathrm (1S)}$ ($p_{\textrm{T}} <15$ GeV/c) = 45.5 ± 3.9 ± 3.5 nb, $\sigma _{\Upsilon \mathrm{(2S)}}$ ($p_{\textrm{T}} <15$ GeV/c) = 22.4 ± 3.2 ± 2.7 nb, and $\sigma _{\Upsilon \mathrm{(3S)}}$ ($p_{\textrm{T}} <15$ GeV/c) = 4.9 ± 2.2 ± 1.0 nb, where the first (second) uncertainty is the statistical (systematic) one. For the first time, the cross sections of the three $\Upsilon$ states, as well as the $\psi \mathrm{(2S)}$ one as a function of $p_{\textrm{T}}$ and $y$, are measured at $\sqrt{s} = 5.02$ TeV at forward rapidity. These measurements also significantly extend the $\textrm{J}/\psi$ $p_{\textrm{T}}$ reach and supersede previously published results. A comparison with ALICE measurements in pp collisions at $\sqrt{s} = 2.76$, 7, 8, and 13 TeV is presented and the energy dependence of quarkonium production cross sections is discussed. Finally, the results are compared with the predictions from several production models.publishedVersio