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Associated production of prompt $J/\psi$ and $\mathit{\Upsilon}$ mesons in $pp$ collisions at $\sqrt{s}=13 \mathrm{TeV}$

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Abstract

The associated production of prompt $J/\psi$ and $\mathit{\mathit{\Upsilon}}$ mesons in $pp$ collisions at a centre-of-mass energy of $\sqrt{s}=13 \mathrm{TeV}$ is studied using LHCb data, corresponding to an integrated luminosity of $4 \mathrm{fb}^{-1}$. The measurement is performed for $J/\psi$ ($\mathit{\Upsilon}$) mesons with a transverse momentum $p_{\mathrm{T}}<10 (30) \mathrm{GeV}/c$ in the rapidity range $2.0<y<4.5$. In this kinematic range, the cross-section of the associated production of prompt $J/\psi$ and $\mathit{\Upsilon}(1S)$ mesons is measured to be $133 \pm 22 \pm 7 \pm 3 \mathrm{pb}$, with a significance of $7.9 \sigma$, and that of prompt $J/\psi$ and $\mathit{\Upsilon}(2S)$ mesons to be $76\pm 21 \pm 4 \pm 7 \mathrm{pb}$, with a significance of $4.9 \sigma$. The first uncertainty is statistical, the second systematic, and the third due to uncertainties on the used branching fractions. This is the first observation of the associated production of $J/\psi$ and $\mathit{\Upsilon}(1S)$ in proton-proton collisions. Differential cross-sections are measured as functions of variables that are sensitive to kinematic correlations between the $J/\psi$ and $\mathit{\Upsilon}(1S)$ mesons. The effective cross-sections of the associated production of prompt $J/\psi$ and $\mathit{\Upsilon}$ mesons are obtained and found to be compatible with measurements using other particle productions.

Figures and captions

Representative Feynman diagrams of the (left) SPS and the (right) DPS process with colour-singlet LDMEs.

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Two-dimensional invariant mass distribution of the $ { J \mskip -3mu/\mskip -2mu\psi } $--$\Upsilon$ candidates projected on (left) the $ { J \mskip -3mu/\mskip -2mu\psi }$ invariant mass $m( { J \mskip -3mu/\mskip -2mu\psi } )$ and (right) the $\Upsilon$ invariant mass $m(\Upsilon)$. The black points with error bars represent the data. The blue solid line represents the result of the fit to the data sample. The red shaded area represents the signal component. The black (dotted) and violet (dashed) lines represent the background where one dimuon candidate is a true meson decay and the other is combinatorial background. The green shaded area indicates the background where both the $ { J \mskip -3mu/\mskip -2mu\psi }$ and $\Upsilon$ candidates are combinatorial background.

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Effective cross-sections measured in different particle production by various experiments. For the LHCb measurements of $ { J \mskip -3mu/\mskip -2mu\psi } \text{--}\Upsilon (1S)$ and $ { J \mskip -3mu/\mskip -2mu\psi } \text{--}\Upsilon (2S)$ effective cross-sections, the error bars (grey boxes) represent the experimental (total) uncertainties. The result for $ { J \mskip -3mu/\mskip -2mu\psi } $--$ { J \mskip -3mu/\mskip -2mu\psi } $ production at LHCb is given as a range covering several model-dependent measurements [46]. Results from other analyses are reproduced from Refs. [1,38].

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Distributions of (top left) invariant mass $m( { J \mskip -3mu/\mskip -2mu\psi } \text{--}\Upsilon (1S))$, (top right) transverse momentum $ p_{\mathrm{T}} ( { J \mskip -3mu/\mskip -2mu\psi } \text{--}\Upsilon (1S))$, (middle left) azimuthal angle difference $|\Delta \phi|$, (middle right) rapidity difference $|\Delta y|$ of $ { J \mskip -3mu/\mskip -2mu\psi } $--${\Y1S} $, and (bottom) $ p_{\mathrm{T}} $ of the $ { J \mskip -3mu/\mskip -2mu\psi }$ and {\Y1S} mesons for data and the pseudodata modelled from previous measurements [74,77]. Black points with error bars represent the data distributions with statistical uncertainties. Red solid lines represent distributions of the DPS pseudodata. Green dashed lines and blue dotted lines represent the DPS distribution together with the lower limit and the upper limit of the SPS distributions, respectively.

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Animated gif made out of all figures.

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Tables and captions

Raw yields from the fit, the efficiency-corrected yields ($N_\mathrm{cor}$) and the signal significances.

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Relative systematic uncertainties on the measurement of the $ { J \mskip -3mu/\mskip -2mu\psi } $--$\Upsilon(1S)$ and $ { J \mskip -3mu/\mskip -2mu\psi } $--${\Y2S} $ cross-sections.

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Created on 26 April 2024.