Measurement of the multiplicity dependence of Υ production ratios in pp collisions at √s = 13 TeV

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A bstract The Υ (2 S ) and Υ (3 S ) production cross-sections are measured relative to that of the Υ (1 S ) meson, as a function of charged-particle multiplicity in proton-proton collisions at a centre-of-mass energy of 13 TeV. The measurement uses data collected by the LHCb experiment in 2018 corresponding to an integrated luminosity of 2 fb − 1 . Both the Υ (2 S )-to- Υ (1 S ) and Υ (3 S )-to- Υ (1 S ) cross-section ratios are found to decrease significantly as a function of event multiplicity, with the Υ (3 S )-to- Υ (1 S ) ratio showing a steeper decline towards high multiplicity. This hierarchy is qualitatively consistent with the comover model predictions, indicating that final-state interactions play an important role in bottomonia production in high-multiplicity events.