Measurement of the exclusive $\Upsilon$ production cross-section in $pp$ collisions at $\sqrt{s}=$7 TeV and 8 TeV

TL;DR

This paper measures the production cross-sections of $$Upsilon(nS)$$ states in proton-proton collisions at 7 and 8 TeV, providing experimental data that aligns well with Standard Model predictions and setting limits on the $$Upsilon(3S)$$ state.

Contribution

First measurement of exclusive $$Upsilon production cross-sections at 7 and 8 TeV in the specified rapidity range, with results consistent with theoretical expectations.

Findings

Measured $$Upsilon(1S)$$ and $$Upsilon(2S)$$ cross-sections with statistical and systematic uncertainties.

Found good agreement between $$Upsilon(1S)$$ cross-section and Standard Model predictions.

Set an upper limit on $$Upsilon(3S)$$ production cross-section at 3.4 pb (95 ext{ }% CL).

Abstract

A study is presented of central exclusive production of $\Upsilon(nS)$ states, where the $\Upsilon(nS)$ resonances decay to the $\mu^+\mu^-$ final state, using $pp$ collision data recorded by the LHCb experiment. The cross-section is measured in the rapidity range $2<y(\Upsilon)<4.5$ where the muons are reconstructed in the pseudorapidity range $2<\eta(\mu^\pm)<4.5$. The data sample corresponds to an integrated luminosity of 2.9 fb$^{-1}$ and was collected at centre-of-mass energies of $7$ TeV and $8$ TeV. The measured $\Upsilon(1S)$ and $\Upsilon(2S)$ production cross-sections are \begin{eqnarray} \sigma(pp \to p\Upsilon(1S)p) &=& 9.0 \pm 2.1 \pm 1.7\textrm{ pb and}\nonumber\\ \sigma(pp \to p\Upsilon(2S)p) &=& 1.3 \pm 0.8 \pm 0.3\textrm{ pb},\nonumber \end{eqnarray} where the first uncertainties are statistical and the second are systematic. The $\Upsilon(1S)$ cross-section is also measured as a function of rapidity and is found to be in good agreement with Standard Model predictions. An upper limit is set at 3.4 pb at the 95\% confidence level for the exclusive $\Upsilon(3S)$ production cross-section, including possible contamination from $\chi_b(3P)\to\Upsilon(3S)\gamma$ decays.