Evidence for a Mass Dependent Forward-Backward Asymmetry in Top Quark Pair Production

Understand

We present a new measurement of the inclusive forward-backward t-tbar production asymmetry and its rapidity and mass dependence.

• The measurements are performed with 5.3 fb^{-1} of p-pbar collisions at \sqrt{s} = 1.96 TeV, recorded with CDF II at the Fermilab Tevatron.
• Significant inclusive asymmetries are observed in the laboratory and t-tbar rest frame, and are consistent with CP conservation under interchange of t and tbar.
• In the t-tbar rest frame, the asymmetry increases with the t-tbar rapidity difference, \Delta(y), and with the invariant mass M_{t-tbar} of the t-tbar system.