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Measurement of $\Upsilon$ production in $pp$ collisions at $\sqrt{s}$= 13 TeV

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Abstract

The production cross-sections of $\Upsilon(1S)$, $\Upsilon(2S)$ and $\Upsilon(3S)$ mesons in proton-proton collisions at $\sqrt{s}$= 13 TeV are measured with a data sample corresponding to an integrated luminosity of $277 \pm 11$ $\rm pb^{-1}$ recorded by the LHCb experiment in 2015. The $\Upsilon$ mesons are reconstructed in the decay mode $\Upsilon\to\mu^{+}\mu^{-}$. The differential production cross-sections times the dimuon branching fractions are measured as a function of the $\Upsilon$ transverse momentum, $p_{\rm T}$, and rapidity, $y$, over the range $0 < p_{\rm T}< 30$ GeV/c and $2.0 < y < 4.5$. The ratios of the cross-sections with respect to the LHCb measurement at $\sqrt{s}$= 8 TeV are also determined. The measurements are compared with theoretical predictions based on NRQCD.

Figures and captions

Dimuon invariant mass distribution of $\Upsilon$ candidates with $0< p_{\rm T} <30 {\mathrm{\,Ge\kern -0.1em V\!/}c} $ and $2.0<y<4.5$. The fit result with the Crystal Ball functions plus an exponential function is also shown. The black dots refer to the data, the blue dashed line refers to the three signals and the green dotted line refers to the background.

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Double-differential cross-sections multiplied by dimuon branching fractions as a function of $p_{\rm T}$ in intervals of $y$ for the (a) $\Upsilon{(1S)} $, (b) $\Upsilon{(2S)} $ and (c) $\Upsilon{(3S)} $ mesons. Statistical and systematic uncertainties are added in quadrature.

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Differential cross-sections multiplied by dimuon branching fractions for the $\Upsilon{(1S)} $ (black solid squares), $\Upsilon{(2S)} $ (red upward triangles) and $\Upsilon{(3S)} $ (blue downward triangles) states (top) versus $p_{\rm T}$ integrated over $y$ between 2.0 and 4.5 and (bottom) versus $y$ integrated over $p_{\rm T}$ from 0 to $15 {\mathrm{\,Ge\kern -0.1em V\!/}c} $. Statistical and systematic uncertainties are added in quadrature. Predictions from NRQCD \cite{Wang:Upsilon2015} for the $\Upsilon{(1S)} $ (black grid shading), $\Upsilon{(2S)} $ (red grid shading) and $\Upsilon{(3S)} $ (blue grid shading) states are overlaid in the top plot.

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The production cross-sections multiplied by dimuon branching fractions integrated over $0< p_{\rm T} <15 {\mathrm{\,Ge\kern -0.1em V\!/}c} $ and $2.0<y<4.5$ versus centre-of-mass energy of $pp$ collisions for the $\Upsilon{(1S)} $ (black solid squares), $\Upsilon{(2S)} $ (red upward triangles) and $\Upsilon{(3S)} $ (blue downward triangles) states. Each set of measurements is offset by a multiplicative factor $m$, which is shown on the plot. Statistical and systematic uncertainties are added in quadrature.

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Ratios of double-differential cross-sections times dimuon branching fractions for (a) $\Upsilon{(2S)} $ to $\Upsilon{(1S)} $ and (b) $\Upsilon{(3S)} $ to $\Upsilon{(1S)} $. Ratios of differential cross-sections times dimuon branching fractions (c) versus $ p_{\rm T} $ integrated over $y$ and (d) versus $y$ integrated over $ p_{\rm T} $ for $\Upsilon{(2S)} $ to $\Upsilon{(1S)} $ (black solid squares) and $\Upsilon{(3S)} $ to $\Upsilon{(1S)} $ (red upward triangles). Statistical and systematic uncertainties are added in quadrature.

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Ratios of double-differential cross-sections between 13 TeV and 8 TeV measurements versus $ p_{\rm T} $ in intervals of $y$ for the (a) $\Upsilon{(1S)} $, (b) $\Upsilon{(2S)} $ and (c) $\Upsilon{(3S)} $ states. Statistical and systematic uncertainties are added in quadrature.

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Ratios of differential cross-sections between 13 TeV and 8 TeV measurements (top) versus $ p_{\rm T} $ integrated over $y$ and (bottom) versus $y$ integrated over $ p_{\rm T} $ for the $\Upsilon{(1S)} $ (black solid squares), $\Upsilon{(2S)} $ (red upward triangles) and $\Upsilon{(3S)} $ (blue downward triangles) states. Statistical and systematic uncertainties are added in quadrature.

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Animated gif made out of all figures.

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Tables and captions

Summary of the relative systematic uncertainties (in $\%$) on the $\Upsilon$ production cross-sections times dimuon branching fractions. Some of the uncertainties are correlated between intervals. For the trigger, track reconstruction and muon identification efficiencies, the uncertainties are larger in the high rapidity region. The uncertainties on the tracking efficiency account for both the limited size of the control samples (first parenthesis) and the impact of different multiplicity between data and simulation on each track (second parenthesis).

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Created on 17 November 2018.Citation count from INSPIRE on 17 November 2018.