Summary of the Precision Measurements of the Electroweak Mixing Angle in the Region of the Z pole

Abstract: This contribution presents a overview of a recent CMS-based determination of the effective leptonic weak mixing angle, $\sin^2θ^\ell_{\mathrm{eff}}$, derived from forward-backward asymmetry measurements in Drell-Yan events at 13 TeV. Although the CMS analysis achieved a major reduction in uncertainties, its overall precision is ultimately limited by residual parton distribution function (PDF) uncertainties. This proceeding highlights the role of complementary CMS observables, which probe distinct parton-density combinations and provide additional constraints beyond those obtained from the original asymmetry measurement alone. The improved analysis yields a substantially reduced total uncertainty, resulting in $\sin^2θ^\ell_{\mathrm{eff}} = 0.23156\pm0.00024$. This result is consistent with the Standard Model prediction and represents the highest precision achieved so far in an individual determination of this parameter.