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Simultaneous measurement of forward-backward asymmetry and top polarization in dilepton final states from t(t)over-bar production at the Tevatron
Joint Nucl Res Inst, Dubna, Russia..
Univ Oklahoma, Norman, OK 73019 USA..
Tata Inst Fundamental Res, Mumbai 400005, Maharashtra, India..
Univ Illinois, Chicago, IL 60607 USA..
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2015 (English)In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 92, no 5, 052007Article in journal (Refereed) Published
Abstract [en]

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
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-264843DOI: 10.1103/PhysRevD.92.052007ISI: 000361670200001OAI: oai:DiVA.org:uu-264843DiVA: diva2:861758
Swedish Research Council
Available from: 2015-10-19 Created: 2015-10-19 Last updated: 2015-10-19Bibliographically approved

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