Measurement of $\Upsilon$ production in $pp$ collisions at $\sqrt{s}=5 \ \rm{TeV}$

Abstract

The production cross-sections of $\Upsilon$ mesons, namely $\Upsilon(1S)$, $\Upsilon(2S)$ and $\Upsilon(3S)$, in $pp$ collisions at $\sqrt{s}=5 \ \rm{TeV}$ are measured with a data sample corresponding to an integrated luminosity of $9.13\pm{0.18} \ \rm{pb}^{-1}$ collected by the LHCb detector. The $\Upsilon$ mesons are reconstructed in the decay mode $\Upsilon \to {\mu}^+ {\mu}^-$. Double differential cross-sections times branching fractions, as functions of the transverse momentum $p_{\rm{T}}$ and the rapidity $y$ of the $\Upsilon$ mesons, are measured in the range $p_{\rm{T}} < 20 \ \rm{GeV}/c$ and $2.0<y<4.5$. The results integrated over these $p_{\rm{T}}$ and $y$ ranges are $\sigma(\Upsilon(1S)) \times\mathcal{B}(\Upsilon(1S)\to {\mu}^+ {\mu}^-) = 2101\pm33\pm83 \ \rm{pb},$ $\sigma(\Upsilon(2S)) \times\mathcal{B}(\Upsilon(2S)\to {\mu}^+ {\mu}^-) = 526\pm20\pm21 \ \rm{pb},$ $\sigma(\Upsilon(3S)) \times\mathcal{B}(\Upsilon(3S)\to {\mu}^+ {\mu}^-) = 242\pm16\pm10 \ \rm{pb},$ where the first uncertainties are statistical and the second are systematic. The ratios of cross-sections between measurements of two different $\Upsilon$ states and between measurements at different center-of-mass energies are determined. The nuclear modification factor of $\Upsilon(1S)$ at $\sqrt{s}=5 \ \rm{TeV}$ is updated as well using the directly measured cross-section results from this analysis.