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

TL;DR

This paper reports on the measurement of the forward-backward asymmetry in Z/gamma* production in proton-proton collisions at 7 TeV using the ATLAS detector, and extracts the effective weak mixing angle, confirming Standard Model predictions.

Contribution

First measurement of forward-backward asymmetry in $pp$ collisions at 7 TeV with ATLAS, providing a precise determination of the effective weak mixing angle.

Findings

Asymmetry measurements agree with Standard Model predictions.

Effective weak mixing angle determined as 0.2308 ± 0.0012.

Results consistent with world average from Particle Data Group.

Abstract

This paper presents measurements from the ATLAS experiment of the forward-backward asymmetry in the reaction $pp\rightarrow Z/\gamma^{*}\rightarrow l^{+}l^{-}$, with $l$ 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 $pp$ 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 $0.2308 \pm 0.0005 \mathrm{(stat.)} \pm 0.0006 \mathrm{(syst.)} \pm 0.0009\mathrm{(PDF)}$, where the first uncertainty corresponds to data statistics,the second to systematic effects and the third to knowledge of the parton density functions. This result agrees with the current world average from the Particle Data Group fit.