This article reports on the inclusive production cross section of several quarkonium states, $\mathrm{J}/\psi$, $\psi {\rm (2S)}$, $\Upsilon\rm(1S)$, $\Upsilon\rm(2S)$, and $\Upsilon\rm(3S)$, 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 ($p_{\rm T}$) and rapidity ($y$) differential cross sections for $\mathrm{J}/\psi$, $\psi {\rm (2S)}$, $\Upsilon\rm(1S)$, and the $\psi {\rm (2S)}$-to-$\mathrm{J}/\psi$ cross section ratios are presented. The integrated cross sections, assuming unpolarized quarkonia, are: $\sigma_{\mathrm{J}/\psi}$($p_{\rm T}<~20$ GeV/c) = 5.88 $\pm$ 0.03 $\pm$ 0.34 $\mu$b, $\sigma_{\psi {\rm (2S)}}$($p_{\rm T}<~12$ GeV/c) = 0.87 $\pm$ 0.06 $\pm$ 0.10 $\mu$b, $\sigma_{\Upsilon\rm(1S)}$($p_{\rm T}<~15$ GeV/c) = 45.5 $\pm$ 3.9 $\pm$ 3.5 nb, $\sigma_{\Upsilon\rm(2S)}$($p_{\rm T}<~15$ GeV/c) = 22.4 $\pm$ 3.2 $\pm$ 2.7 nb, and $\sigma_{\Upsilon\rm(3S)}$($p_{\rm T}<~15$ GeV/c) = 4.9 $\pm$ 2.2 $\pm$ 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 $\psi {\rm (2S)}$ one as a function of $p_{\rm T}$ and $y$, are measured at $\sqrt{s} = 5.02$ TeV at forward rapidity. These measurements also significantly extend the $\mathrm{J}/\psi$ $p_{\rm T}$ 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.
Eur. Phys. J. C 83 (2023) 61
e-Print: arXiv:2109.15240 | PDF | inSPIRE
CERN-EP-2021-197
Figure group
Figure 1
Examples of fit to the OS dimuon invariant mass distribution in the mass region $2 < m_{\mu^{+}\mu^{-}} < 5$ GeV/$c^{2}$ for $\pt < 20$ \GeVc (left), and $7< m_{\mu^{+}\mu^{-}} < 13$ GeV/$c^{2}$ for $\pt < 15$ \GeVc (right). The \jpsi, $\psi$(2S) and $\Upsilon$(nS) signals are modelled with extended Crystal Ball functions, while the background is described by a pseudo Gaussian with a width increasing linearly with the invariant mass. The fit is performed on the full data sample. The widths of the \psitwos, \upstwos and \upsthrees, for these examples, are fixed to 73 \MeVc, 156 \MeVc and 161 \MeVc, respectively. |   |
Figure 5
The left and right panels show the \pt dependence for the inclusive \psitwos production cross section in \pp collisions at $\s = 5.02$ TeV. The results are compared with the theory predictions based on NRQCD (left) and CEM (right) models. The calculation of the non-prompt contribution from FONLL calculations are also shown separately. See text for details. |   |
Figure 9
Transverse momentum dependence of the inclusive \jpsi cross section, at forward \rapidity, measured in pp collisions at $\sqrt{s} = 5.02$, 7 , 8 , and 13 TeV (top panels), and ratio of the measurements at 5.02, 7, and 8 TeV to the 13 TeV data (bottom panels). The data are compared with the NRQCD theoretical calculations from Butenschön \etal + FONLL (left panels) and with theoretical calculations from ICEM + FONLL (right panels) . |   |
Figure 10
Rapidity dependence of the inclusive \jpsi (left) and \psitwos (right) cross section, at forward \rapidity, measured in pp collisions at $\s = 5.02$, 7 , 8 , and 13 TeV (top panels), and ratio of the measurements at 5.02, 7, and 8 TeV to the 13 TeV data (bottom panels). The data are compared with theoretical calculations from ICEM + FONLL . |   |
Figure 11
Transverse momentum dependence of the inclusive \psitwos cross section, at forward \rapidity, measured in pp collisions at $\s = 5.02$, 7 , 8 , and 13 TeV (top panels), and ratio of the measurements at 5.02, 7, 8 TeV to the 13 TeV data (bottom panels). The data are compared with the NRQCD theoretical calculations from Butenschön \etal + FONLL (left panels) and with theoretical calculations from ICEM + FONLL (right panels) . |   |
Figure 12
Inclusive \psitwos-to-\jpsi cross section ratio as a function of \pt, at forward \rapidity, in pp collisions at $\s = 5.02$, 7 , 8 , and 13 TeV (left panel). The data at $\s = 5.02$ TeV are compared with NRQCD theoretical calculations from Butenschön \etal + FONLL and with theoretical calculations from ICEM + FONLL (right panel). |   |
Figure 14
Inclusive \psitwos-to-\jpsi cross section ratio (left) and \jpsi, \psitwos, \upsones, \upstwos, and \upsthrees \pt-integrated cross section per unit of rapidity (right) as a function of the collision energy in pp collisions . In the left panel, the systematic boxes include the BR uncertainties from both resonances, on top of the MC input and signal extraction systematic uncertainties. The 13 TeV data point is computed from the published individual \jpsi and \psitwos \pt-integrated cross sections. The statistical and systematic uncertainties are assumed to be uncorrelated between the resonances when computing the ratio. In the right panel, the luminosity and branching ratio uncertainties are included in the systematic boxes. The data are compared with theoretical calculations from ICEM + FONLL . |   |
Figure A.1
Inclusive \psitwos-to-\jpsi cross section ratio as a function of \pt, at forward \rapidity, in pp collisions at $\s$ = 7 (top left), 8 (top right), and 13 TeV (bottom left). The data are compared with NRQCD theoretical calculations from Butenschön \etal + FONLL and with theoretical calculations from ICEM + FONLL . |    |