Production of Υ(nS) mesons in Pb+Pb and pp collisions at 5.02 TeV

A measurement of the production of vector bottomonium states, Υ(1S), Υ(2S), and Υ(3S), in Pb+Pb and pp collisions at a center-of-mass energy per nucleon pair of 5.02 TeV is presented. The data correspond to integrated luminosities of 1.38~nb⁻¹ of Pb+Pb data collected in 2018, 0.44 nb⁻¹ of Pb+Pb data collected in 2015, and 0.26 fb⁻¹ of pp data collected in 2017 by the ATLAS detector at the Large Hadron Collider. The measurements are performed in the dimuon decay channel for transverse momentum p^μμ_T<30~ GeV, absolute rapidity |y^μμ|<1.5, and Pb+Pb event centrality 0-80%. The production rates of the three bottomonium states in Pb+Pb collisions are compared with those in pp collisions to extract the nuclear modification factors as functions of event centrality, p^μμ_T, and |y^μμ|. In addition, the suppression of the excited states relative to the ground state is studied. The results are compared with theoretical model calculations.