Measurement of the Drell–Yan forward-backward asymmetry and of the effective leptonic weak mixing angle in proton-proton collisions at s=13TeV

The forward-backward asymmetry in Drell–Yan production and the effective leptonic electroweak mixing angle are measured in proton-proton collisions at $\sqrt{s}=13$ TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 138${\text{fb}}^{-1}$. The measurement uses both dimuon and dielectron events, and is performed as a function of the dilepton mass and rapidity. The unfolded angular coefficient $A_4$ is also extracted, as a function of the dilepton mass and rapidity. Using the CT18Z set of parton distribution functions, we obtain ${\sin }^2{\theta }_{\text{eff}}^{\ell }=0.23152\pm 0.00031$, where the uncertainty includes the experimental and theoretical contributions. The measured value agrees with the standard model fit result to global experimental data. This is the most precise ${\sin }^2{\theta }_{\text{eff}}^{\ell }$ measurement at a hadron collider, with a precision comparable to the results obtained at LEP and SLD.