Using Z-hadron correlations to probe the medium response in PbPb and pp collisions at √ˢNN = 5.02 TeV

Abstract

The first measurement of Z-hadron two-particle correlation function are reported in PbPb collisions at √ˢNN = 5.02 TeV, using the PbPb collision data taken in 2018. The integrated luminosity of the PbPb data is 1.67 ±0.03 nb⁻¹ which made the analysis possible for the first time. Collision data with at at least one Z boson with 40 <pT <200 GeV/c are analyzed. The azimuthal angle distributions with respect to the Z bosons, whih are sensitive to modification of in-medium parton shower and medium recoils, are measured in central PbPb collisions. A significant modification of the two particle correlation in pseudorapidity difference and azimuthal angle difference is observed with respect to the reference measured in pp collisions. Those results are compared to phenomenological models that include medium-recoil, medium response and thermalization of the QGP wakes.