Abstract
We present a measurement of the charge asymmetry in top quark pair production using an integrated luminosity of 1.09 fb-1 collected with the CMS detector. Top quark pairs with a signature of one electron or muon and four or more jets, at least one of them b tagged, are selected. At the LHC a small charge asymmetry in the rapidity distributions of top and antitop quarks is predicted. Therein slightly broader rapidity distributions for top quarks are expected, while antitop quarks are produced more centrally and possess narrower rapidity distributions. We determine the charge asymmetry based on two different sensitive variables and the results are compared with the most precise standard model theory predictions using a dedicated unfolding technique.
Highlights
In the Standard Model (SM), a small charge asymmetry in tt production via quark-antiquark annihilation is predicted
We present a measurement of the charge asymmetry in top quark pair production using an integrated luminosity of 1.09 fb−1 collected with the Compact Muon Solenoid (CMS) detector
The analysis [13] presented here provides the measurement of the charge asymmetry in tt events using a dataset corresponding to an integrated luminosity of 1.09 fb−1
Summary
In the Standard Model (SM), a small charge asymmetry in tt production via quark-antiquark annihilation is predicted. The CDF collaboration reports an even larger asymmetry compared to the SM prediction at high tt invariant masses [6] These results have led to speculations that the large asymmetry might be generated by additional axial couplings of the gluon or by heavy particles with unequal vector and axial-vector couplings to top quarks and antiquarks. The SM [5] and prediction for ∆y2 it fisorA∆Cy|η(t|hiseoArCηy()th=eo0ry.0)1=150.±0103.60±0006.00[50]8, where the uncertainties arise from scale variations and particle density function uncertainties These values are much smaller than the SM predictions for the Tevatron, because of the large fraction of gluon-gluon induced tt production
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