Investigation of the difference in the angular distributions of $Z\to \ell^{+}\ell^{-}$ events produced in quark-antiquark, quark-gluon and gluon-gluon collisions
Measurements of the angular distributions of Z boson-decay leptons at the Large Hadron Collider (LHC) are of interest in QCD studies and precision electroweak measurements. Z boson production at the LHC is dominated by quark-gluon processes and the quark-antiquark process accounts for only 40\% of the cross section. We investigate the theoretical predictions (using the POWHEG-minnlops event generator) for the difference in the angular distributions of $ pp \to γ^{*}/Z \to \ell^+\ell^-$ ($ μ^+μ^-$ or $e^{+}e^{-}$) events produced via quark-antiquark, quark-gluon , and gluon-gluon processes. The study is done for proton-proton collisions at the Large Hadron Collider (LHC) at $\sqrt{s} = 13$ TeV. We investigate the angular coefficients $A_0$ and $A_2$ (for $θ_{CS}$ and $ϕ_{CS}$ distributions in the Collins-Soper frame) for the different processes as a function of the Z boson rapidity, transverse momentum and final state jet multiplicity, and propose how these can be investigated experimentally at the LHC.