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

Abstract

We present a new measurement of the inclusive forward-backward tt production asymmetry and its rapidity and mass dependence. The measurements are performed with data corresponding to an integrated luminosity of 5:3 fb1 of pp collisions at ffisffiffi p ¼ 1:96 TeV, recorded with the CDF-II Detector at the Fermilab Tevatron. Significant inclusive asymmetries are observed in both the laboratory frame and the tt rest frame, and in both cases are found to be consistent with CP conservation under interchange of t and t. In the tt rest frame, the asymmetry is observed to increase with the tt rapidity difference, y, and with the invariant mass Mtt of the tt system. Fully corrected parton-level asymmetries are derived in two