Simultaneous measurement of forward backward asymmetry and top polarization in dilepton final states from tt production at the Tevatron
We present a simultaneous measurement of the forward backward asymmetry and the top quark polarization in t (t) over bar production in dilepton final states using 9.7 fb( 1) of proton antiproton collisions at root s 1.96 TeV with the D0 detector. To reconstruct the distributions of kinematic observables we employ a matrix element technique that calculates the likelihood of the possible t (t) over bar kinematic configurations. After accounting for the presence of background events and for calibration effects, we obtain a forward backward asymmetry of A(t (t) over bar) (15.0 6.4(stat) 4.9(syst) and a top quark polarization times spin analyzing power in the beam basis of kappa P (7.2 10.5(stat) 4.2(syst) with a correlation of 56% between the measurements. If we constrain the forward backward asymmetry to its expected standard model value, we obtain a measurement of the top polarization of kappa P (11.3 9.1(stat) 1.9(syst) If we constrain the top polarization to its expected standard model value, we measure a forward backward asymmetry of A(t (t) over bar) (17.5 5.6(stat) 3.1(syst) A combination with the D0 A(t (t) over bar) measurement in the lepton jets final state yields an asymmetry of A(t (t) over bar) (11.8 2.5(stat) 1.3(syst) Within their respective uncertainties, all these results are consistent with the standard model expectations.