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Production of $J/\psi$ and $\Upsilon$ mesons in $pp$ collisions at $\sqrt{s}$ = 8 TeV

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Abstract

The production of J/psi and Upsilon mesons in pp collisions at sqrt(s) = 8 TeV is studied with the LHCb detector. The J/psi and Upsilon mesons are reconstructed in the mu+mu- decay mode and the signal yields are determined with a fit to the mu+mu- invariant mass distributions. The analysis is performed in the rapidity range 2.0<y<4.5 and transverse momentum range 0<p_T<14(15) GeV/c of the J/psi(Upsilon) mesons. The J/psi and Upsilon production cross-sections and the fraction of J/psi mesons from b-hadron decays are measured as a function of the meson p_T and y.

Figures and captions

Projections of the fit result for a selected bin in $p_{\rm T}$ and $y$ for (a) the $ J/\psi$ invariant dimuon mass and (b) $t_z$. For the former, the total fitted function is shown (blue solid line) together with the signal distribution (red dotted line). In the $t_z$ projection the total fitted function is shown together with the $ J/\psi \mathrm{from} b $ component, the prompt signal, the background and the tail component due to the association of a $ J/\psi$ candidate with a wrong PV.

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Invariant mass distribution of the selected $\varUpsilon\rightarrow \mu^+\mu^-$ candidates in the range $ p_{\rm T} <15\, {\mathrm{\,GeV\!/}c} $ and $2.0<y<4.5$. The three peaks correspond to the $\varUpsilon(1S)$, $\varUpsilon(2S)$ and $\varUpsilon(3S)$ meson signals (from left to right). The superimposed curve and the signal yields (dotted) are the result of the fit described in the text.

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Differential production cross-section for (a) prompt $ J/\psi$ mesons and (b) $ J/\psi \mathrm{from} b $ as a function of $p_{\rm T}$ in bins of $y$. It is assumed that prompt $ J/\psi$ mesons are produced unpolarised. The errors are the quadratic sums of the statistical and systematic uncertainties.

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Differential production cross-section as a function of $y$ integrated over $p_{\rm T}$ , for (a) unpolarised $\mathrm{prompt} J/\psi$ mesons and (b) $ J/\psi \mathrm{from} b $ . The errors are the quadratic sums of the statistical and systematic uncertainties.

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Fraction of $ J/\psi \mathrm{from} b $ as a function of $p_{\rm T}$ , in bins of $y$.

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Double-differential cross-sections times dimuon branching fractions as a function of $p_{\rm T}$ in bins of $y$ for (a) the $\varUpsilon(1S)$, (b) $\varUpsilon(2S)$ and (c) $\varUpsilon(3S)$ mesons.

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Differential production cross-sections for $\varUpsilon(1S)$, $\varUpsilon(2S)$ and $\varUpsilon(3S)$ mesons times dimuon branching fraction (a) as a function of $ p_{\rm T} $ integrated over $y$, and (b) as a function of $y$ integrated over $ p_{\rm T} $.

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{\it } Ratio of the $\varUpsilon(2S)$ to $\varUpsilon(1S)$ and $\varUpsilon(3S)$ to $\varUpsilon(1S)$ cross-sections times dimuon branching fractions (a) as a function of $ p_{\rm T} $ integrated over $y$, and (b) as a function of $y$ integrated over $ p_{\rm T} $.

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Comparison of the differential cross-section for the production of prompt $ J/\psi$ meson (under the assumption of zero polarisation) as a function of $ p_{\rm T} $ with direct production in an NLO NRQCD model [47,48] (orange diagonal shading), an NNLO* CSM [10] (solid yellow) and an NLO CSM [7] (blue vertical shading). The points show the measurements reported in this analysis.

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Differential production cross-section for $ J/\psi \mathrm{from} b $ (a) as a function of $p_{\rm T}$ in the fiducial range $2.0<y<4.5$, and (b) as a function of $y$ in the fiducial range $ p_{\rm T} <14\, {\mathrm{\,GeV\!/}c} $. The FONLL prediction [46,50] is shown in yellow. The points show the measurements reported in this analysis.

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Predictions based on the FONLL formalism [46,50] for the production cross-section for $ J/\psi \mathrm{from} b $ in the fiducial range $0< p_{\rm T} <14\, {\mathrm{\,GeV\!/}c} $ and $2.0<y<4.5$ (yellow band). The uncertainty includes contributions from the renormalisation scale, quark masses and the choice of PDF set. The black dotted line shows the central value of the prediction. The points show the LHCb measurements at $\sqrt{s}=2.76$ [14], 7 [12], and 8$\,\mathrm{\,TeV} $.

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Comparison of the differential production cross-sections times dimuon branching fractions for (a) $\varUpsilon(1S)$, (b) $\varUpsilon(2S)$ and (c) $\varUpsilon(3S)$ mesons as a function of $ p_{\rm T} $ with direct production in an NNLO$^*$ CSM [9] (solid yellow) and an NLO CSM [7] (blue vertical shading) model. The points show the measurements reported in this analysis.

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Animated gif made out of all figures.

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Tables and captions

Selection criteria for the $ J/\psi$ and $\varUpsilon$ meson analyses. Criteria common to both analyses are displayed between the two columns.

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Relative systematic uncertainties (in %) on the $ J/\psi$ and $\varUpsilon$ cross-section results and on the fraction of $ J/\psi \mathrm{from} b $ .

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Differential production cross-section ${\rm d}\sigma/{\rm d}y$ in nb for $\mathrm{prompt} J/\psi$ mesons (assumed unpolarised) and for $ J/\psi \mathrm{from} b $ , integrated over $p_{\rm T}$ . The first uncertainty is statistical, the second (third) is the part of the systematic uncertainty that is uncorrelated (correlated) between bins.

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Double-differential cross-section $\frac{{\rm d}^2\sigma}{{\rm d}p_{\rm T}{\rm d}y}$ in nb/( $ {\mathrm{\,GeV\!/}c}$ ) for prompt $ J/\psi$ meson production in bins of of $p_{\rm T}$ and $y$, with the assumption of no polarisation. The first error is statistical, the second is the component of the systematic uncertainty that is uncorrelated between bins and the third is the correlated component.

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Double-differential cross-section $\frac{{\rm d}^2\sigma}{{\rm d}p_{\rm T}{\rm d}y}$ in nb/( $ {\mathrm{\,GeV\!/}c}$ ) for the production of $ J/\psi \mathrm{from} b $ in bins of $p_{\rm T}$ and $y$. The first error is statistical, the second is the component of the systematic uncertainty that is uncorrelated between bins and the third is the correlated component.

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Fraction of $ J/\psi \mathrm{from} b $ (in %) in bins of of $p_{\rm T}$ and $y$. The first uncertainty is statistical and the second systematic (uncorrelated between bins).

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Double-differential production cross-sections $\frac{{\rm d}^2\sigma}{{\rm d}p_{\rm T}{\rm d}y}\times \mathcal{B}^{1S}$ in pb/( $ {\mathrm{\,GeV\!/}c}$ ) for the $\varUpsilon(1S)$ meson in bins of transverse momentum and rapidity, assuming no polarisation. The first error is statistical, the second is the component of the systematic uncertainty that is uncorrelated between bins and the third is the correlated component.

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Double-differential production cross-sections $\frac{{\rm d}^2\sigma}{{\rm d}p_{\rm T}{\rm d}y}\times \mathcal{B}^{2S}$ in pb/( $ {\mathrm{\,GeV\!/}c}$ ) for the $\varUpsilon(2S)$ meson in bins of transverse momentum and rapidity, assuming no polarisation. The first error is statistical, the second is the component of the systematic uncertainty that is uncorrelated between bins and the third is the correlated component. Regions where the number of events was not large enough to perform a measurement are indicated with a dash.

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Double-differential production cross-sections $\frac{{\rm d}^2\sigma}{{\rm d}p_{\rm T}{\rm d}y}\times \mathcal{B}^{3S}$ in pb/( $ {\mathrm{\,GeV\!/}c}$ ) for the $\varUpsilon(3S)$ meson in bins of transverse momentum and rapidity, assuming no polarisation. The first error is statistical, the second is the component of the systematic uncertainty that is uncorrelated between bins and the third is the correlated component. Regions where the number of events was not large enough to perform a measurement are indicated with a dash.

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Ratios of cross-sections $\varUpsilon(2S)\rightarrow\mu^+\mu^-$ and $\varUpsilon(3S)\rightarrow\mu^+\mu^-$ with respect to {$\varUpsilon(1S)\rightarrow\mu^+\mu^-$} as a function of $ p_{\rm T} $ in the range $2.0<y<4.0$, assuming no polarisation. The first error is statistical, the second is the component of the systematic uncertainty that is uncorrelated between bins and the third is the correlated component.

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Ratios of cross-sections $\varUpsilon(2S)\rightarrow\mu^+\mu^-$ and $\varUpsilon(3S)\rightarrow\mu^+\mu^-$ with respect to {$\varUpsilon(1S)\rightarrow\mu^+\mu^-$} as a function of $y$ in the range $2.0<y<4.0$, assuming no polarisation. The first error is statistical, the second is the component of the systematic uncertainty that is uncorrelated between bins and the third is the correlated component.

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Supplementary Material [file]

This ZIP file contains supplemetary material for the publication LHCb-PAPER-2013-016. The files are the three formats of the Figure 13, whose description is below. Fig.13: Comparison of the differential cross-section for the production of prompt J/psi as a function of y with direct production in a NLO NRQCD model

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Created on 09 December 2018.Citation count from INSPIRE on 09 December 2018.