Measurement of the top quark forward-backward production asymmetry and its dependence on event kinematic properties

Abstract

We present new measurements of the inclusive forward-backward tt̅ production asymmetry, A[subscript FB], and its dependence on several properties of the tt̅ system. The measurements are performed with the full Tevatron data set recorded with the CDF II detector during pp̅ collisions at √s=1.96 TeV, corresponding to an integrated luminosity of 9.4 fb[superscript -1]. We measure the asymmetry using the rapidity difference Δy=y[subscript t]-y[subscript t̅]. Parton-level results are derived, yielding an inclusive asymmetry of 0.164±0.047(stat+syst). We establish an approximately linear dependence of A[subscript FB] on the top-quark pair mass M[subscript tt̅] and the rapidity difference |Δy| at detector and parton levels. Assuming the standard model, the probabilities to observe the measured values or larger for the detector-level dependencies are 7.4×10[superscript -3] and 2.2×10[superscript -3] for M[subscript tt̅] and |Δy| respectively. Lastly, we study the dependence of the asymmetry on the transverse momentum of the tt̅ system at the detector level. These results are consistent with previous lower-precision measurements and provide additional quantification of the functional dependencies of the asymmetry.