Measurement of the forward-backward asymmetry of electron and muon pair-production in pp collisions at $\sqrt {S}$=7 TeV with the ATLAS detector

This talk presents measurements from the ATLAS experiment of the forward-backward asymmetry in the reaction pp $\it \rightarrow Z/\gamma \rightarrow l^{+} l{-}$ (with being electrons or muons) and the extraction of the effective weak mixing angle. The results are based on the full set of data collected in 2011 in $\it pp$ collisions at the LHC at $\sqrt {s} = 7 TeV$, corresponding to an integrated luminosity of 4.8 $fb^{-1}$. The measured asymmetry values are found to be in agreement with the corresponding Standard Model predictions. The combination of the muon and electron channels yields a value of the effective weak mixing angle of $sin^{2} \theta _{eff}^{lept} $ -0.2308 $\pm 0.0005$(stat.) $\pm 0.0006$(syst.) $\pm 0.0009$(PDF). This result agrees with the current world average from the Particle Data Group fit. An estimate for the asymmetry parameter $\it A_{\mu}$ is also presented