Abstract
We present a measurement of the charge asymmetry in top-antitop production using data corresponding to an integrated luminosity of 0.70 fb-1 of proton-proton collisions at √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 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: AC = (N(|ΔY| > 0) − N(|ΔY| < 0)) / (N(|ΔY| > 0) + N(|ΔY| < 0)). To allow comparisons with theory calculations, a Bayesian unfolding technique is applied to correct the measured |ΔY| distributions for acceptance and detector effects. The top charge asymmetry in both channels (e and mu) after correction is measured to be: AC = -0.009 ± 0.023(stat) ± 0.032(syst) (e+jets channel) and AC = -0.028 ± 0.019(stat) ± 0.022(syst) (μ+jets channel) giving a combined result of : AC = -0.024 ± 0:016(stat) ± 0.023(syst). These results are compatible with the Standard Model predictions of AC = 0.006.
Highlights
Background determinationThe estimation of the background is done by using a datadriven technique
This paper presents the measurement of the charge asymmetry AC using ttevents decaying semi-leptonically to either an electron or muon and at least four jets using data corresponding to an integrated luminosity of 0.7 f b−1 [3]
The method used for evaluating the Quantum ChromoDynamics (QCD) multijet background with fake and non-prompt leptons in both the electron and muon channels is the so called ’ Matrix Method’, which relies on defining loose and tight event samples and measuring the efficiencies of real and fake ( f ake) loose leptons to be selected as tight leptons
Summary
The method used for evaluating the QCD multijet background with fake and non-prompt leptons in both the electron and muon channels is the so called ’ Matrix Method’, which relies on defining loose and tight event samples and measuring the efficiencies of real ( real) and fake ( f ake) loose leptons to be selected as tight leptons. In addition to the backgrounds mentioned previousely, there are small background contributions (the single top production, Z + jets and diboson events) which are evaluated using MC normalized to the event (N)NLO cross sections
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
