Measurement of the charge asymmetry in top quark pair production in pp collisions at $\sqrt{s}=7$ TeV using the ATLAS detector

Abstract

We present a measurement of the charge asymmetry in top-antitop production using data corresponding to an integrated luminosity of $0.70f{b}^{-1}$ of proton-proton collisions at $\sqrt{s}=7$ TeV collected by the ATLAS detector. The top pair events decaying semileptonically (lepton+jets channel) to either an electron or muon, missing transverse energy and at least four jets are selected. The reconstruction of the $t\bar{t}$ events was performed using a kinematic likelihood approach. The difference of absolute values of top and antitop rapidities is used to define the charge asymmetry: $A_C=(N(|\Delta Y|>0)-N(|\Delta Y|<0))/(N(|\Delta Y>0)+N(|\Delta Y|<0))$. To allow comparisons with theory calculations, a Bayesian unfolding technique is applied to correct the measured $|\Delta Y|$ distributions for acceptance and detector effects. The top charge asymmetry in both channels (e and mu) after correction is measured to be: $A_C=-0.009\pm 0.023(stat)\pm 0.032(syst)$ (e+jets channel) and $A_C=-0.028\pm 0.019(stat)\pm 0.022(syst)$ ($\mu$+jets channel) giving a combined result of : $A_C=-0.024\pm 0.016(stat)\pm 0.023(syst)$. These results are compatible with the Standard Model predictions of $A_C=0.006$.

Presented at the 2011 Hadron Collider Physics symposium (HCP-2011), Paris, France, November 14-18 2011, 3 pages, 4 figures

References in corpus (1)

• Top Quarks, Axigluons and Charge Asymmetries at Hadron Colliders

Cited by in corpus (1)

• Improving top quark induced charge asymmetries at the LHC using ttbar transverse momentum