Simultaneous measurement of forward-backward asymmetry and top polarization in dilepton final states from t(t)over-bar production at the Tevatron
2015 (English)In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 92, no 5, 052007Article in journal (Refereed) Published
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.
Place, publisher, year, edition, pages
2015. Vol. 92, no 5, 052007
IdentifiersURN: urn:nbn:se:uu:diva-264843DOI: 10.1103/PhysRevD.92.052007ISI: 000361670200001OAI: oai:DiVA.org:uu-264843DiVA: diva2:861758
FunderSwedish Research Council