# Measurement of $\Upsilon$ production in $pp$ collisions at $\sqrt{s} = 7$ TeV

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## Abstract

The production of Upsilon(1S), Upsilon(2S) and Upsilon(3S) mesons in proton-proton collisions at the centre-of-mass energy of sqrt(s)=7 TeV is studied with the LHCb detector. The analysis is based on a data sample of 25 pb-1 collected at the Large Hadron Collider. The Upsilon mesons are reconstructed in the decay mode Upsilon -> mu+ mu- and the signal yields are extracted from a fit to the mu+ mu- invariant mass distributions. The differential production cross-sections times dimuon branching fractions are measured as a function of the Upsilon transverse momentum pT and rapidity y, over the range pT < 15 GeV/c and 2.0 < y < 4.5. The cross-sections times branching fractions, integrated over these kinematic ranges, are measured to be sigma(pp -> Upsilon(1S) X) x B(Upsilon(1S)->mu+ mu-) = 2.29 {\pm} 0.01 {\pm} 0.10 -0.37 +0.19 nb, sigma(pp -> Upsilon(2S) X) x B(Upsilon(2S)->mu+ mu-) = 0.562 {\pm} 0.007 {\pm} 0.023 -0.092 +0.048 nb, sigma(pp -> Upsilon(3S) X) x B(Upsilon(3S)->mu+ mu-) = 0.283 {\pm} 0.005 {\pm} 0.012 -0.048 +0.025 nb, where the first uncertainty is statistical, the second systematic and the third is due to the unknown polarisation of the three Upsilon states.

 Invariant mass distribution of the selected $\varUpsilon\rightarrow \mu^+\mu^-$ candidates in the range $p_{\rm T} <15 {\mathrm{\,GeV\!/}c}$ and $2.0 ## Tables and captions  Summary of the relative systematic uncertainties on the cross-section measurements. Ranges indicate variations depending on the ($ p_{\rm T} ,y$) bin and the$\varUpsilon$state. All uncertainties are fully correlated among the bins. Table_1.pdf [34 KiB] HiDef png [82 KiB] Thumbnail [12 KiB] tex code Double differential cross-section$\varUpsilon(1S)\rightarrow\mu^+\mu^-$as a function of rapidity and transverse momentum, in pb/($ {\mathrm{\,GeV\!/}c}$). The first uncertainty is statistical, the second is systematic, and the third is due to the unknown polarisation of the$\varUpsilon(1S)$. Table_2.pdf [67 KiB] HiDef png [146 KiB] Thumbnail [23 KiB] tex code Double differential cross-section$\varUpsilon(2S)\rightarrow\mu^+\mu^-$as a function of rapidity and transverse momentum, in pb/($ {\mathrm{\,GeV\!/}c}$). The first uncertainty is statistical, the second is systematic, and the third is due to the unknown polarisation of the$\varUpsilon(2S)$. Regions where the number of events was not sufficient to perform a measurement are indicated with a dash. Table_3.pdf [67 KiB] HiDef png [133 KiB] Thumbnail [22 KiB] tex code Double differential cross-section$\varUpsilon(3S)\rightarrow\mu^+\mu^-$as a function of rapidity and transverse momentum, in pb/($ {\mathrm{\,GeV\!/}c}$). The first uncertainty is statistical, the second is systematic, and the third is due to the unknown polarisation of the$\varUpsilon(3S)$. Regions where the number of events was not sufficient to perform a measurement are indicated with a dash. Table_4.pdf [66 KiB] HiDef png [130 KiB] Thumbnail [22 KiB] tex code Ratios of cross-sections$\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

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