Correlation of Y meson production with the underlying event in pp collisions measured by the ATLAS experiment

The multiplicity and distributions of kinematic variables of charged particles produced in association with an $\Upsilon$ meson are measured in proton-proton collisions using the data collected by the ATLAS experiment at the LHC. The analysis uses a full Run 2 data set at $\sqrt{s}=13$ TeV, corresponding to the integrated luminosity of 139 fb$^{-1}$. The measurement is performed separately for the first three $\Upsilon\left(n\mathrm{S}\right)$ states in several intervals of $\Upsilon$ transverse momenta. At $\Upsilon$ transverse momentum close to zero, the associated charged-particle multiplicity is measured to be smaller by $12\pm1$\% in collisions where $\Upsilon\left(2\mathrm{S}\right)$ is observed compared to the collisions with $\Upsilon\left(1\mathrm{S}\right)$. For $\Upsilon\left(3\mathrm{S}\right)$ this difference is $17\pm4$\%. These differences decrease with increasing transverse momentum of the $\Upsilon$ states.