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Simultaneous measurement of forward-backward asymmetry and top polarization in dilepton final states from t¯t production at the Tevatron
Baringer, Philip S. Bean, Alice Wilson, Graham Wallace D0 Collaboration
Baringer, Philip S.
Bean, Alice
Wilson, Graham Wallace
D0 Collaboration
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Abstract
We present a simultaneous measurement of the forward-backward asymmetry and the top-quark polarization in tt¯ production in dilepton final states using 9.7 fb−1 of proton-antiproton collisions at 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 tt¯ kinematic configurations. After accounting for the presence of background events and for calibration effects, we obtain a forward-backward asymmetry of Att¯=(15.0±6.4(stat)±4.9(syst))% and a top-quark polarization times spin analyzing power in the beam basis of κP=(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 κP=(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 Att¯=(17.5±5.6(stat)±3.1(syst))%. A combination with the D0 Att¯ measurement in the lepton+jets final state yields an asymmetry of Att¯=(11.8±2.5(stat)±1.3(syst))%. Within their respective uncertainties, all these results are consistent with the standard model expectations.
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2015-09-22
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American Physical Society
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BeanAlice_2015.pdf
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Abazov, V. M., Abbott, B., Acharya, B. S., Adams, M., Adams, T., Agnew, J. P., … Askew, A. (2015). Simultaneous measurement of forward-backward asymmetry and top polarization in dilepton final states from t t ¯ production at the Tevatron . Phys. Rev. D, 92(5). doi:10.1103/physrevd.92.052007