| Early measurements of a large forward-background asymmetry at the CDF [1, 2, 3, 4] and Dempty [5, 6] experiments at Fermilab have generated much recent interest, but were hampered by large uncertainties. We present here a new measurement of the corrected forward-backward asymmetry of pair-produced top quarks, using a high-statistics sample with much improved precision. We study the rapidity, ytop, of the top quark production angle with respect to the incoming parton momentum in both the lab and tt¯ rest frames. We find the corrected forward-backward asymmetries to be Appfb=0.150+/- 0.050stat+/-0.024syst Attfb=0.158+/-0 .072stat+/-0.024syst These results should be compared with the small lab pp¯ frame charge asymmetry expected in QCD at NLO, Afb = 0.050 +/- 0.015 [7, 8, 9, 10]. Additionally, we introduce a measurement of the A fb rapidity dependence dAfbd Dy . We find this to be Attfb Dy1.0=0.6 11+/-0.210stat+/-0.246syst which we compare with model predictions 0.039 +/- 0.006 and 0.123 +/- 0.018 for the inner and outer rapidities, respectively. |
