Upsilon - underlying event correlations in pp collisions at ATLAS

This talk presents a new measurement studying the relationship between the production of hard and soft particles through the correlation of Upsilon meson states with the inclusive charged particle yields in 13 TeV pp collisions. These correlations, and in particular their comparison between excited and ground state Upsilons meson, lead to surprising conclusions about heavy quarkonium production and hadronization. Measurements of charged particles in events with different Upsilon states are studied in intervals of Upsilon momentum. The analysis is performed using the full-luminosity ATLAS Run-2 13 TeV pp data. This measurement benefits from novel application of statistical techniques to remove the combinatorial and pileup backgrounds leading to increased sensitivity. A description of the technical challenges associated with an inclusive hadron analysis in high-pileup pp data will be shown, as well as the results and their physics implications.