Abstract

The forward-backward asymmetry in Drell–Yan production and the effective leptonic electroweak mixing angle are measured in proton-proton collisions at s=13 TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 138fb−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 A4 is also extracted, as a function of the dilepton mass and rapidity. Using the CT18Z set of parton distribution functions, we obtain sin2⁡θeffℓ=0.23152±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 sin2⁡θeffℓ measurement at a hadron collider, with a precision comparable to the results obtained at LEP and SLD. © 2025 CERN for the benefit of the CMS Collaboration