Research Papers in Physics and Astronomy


Date of this Version



PHYSICAL REVIEW D 84, 052005 (2011)


Copyright 2011 American Physical Society; DOI: 10.1103/PhysRevD.84.052005


We present a direct measurement of the mass difference between top and antitop quarks (∆m) in lepton + jets tt final states using the ‘‘matrix element’’ method. The purity of the lepton + jets sample is enhanced for tt events by identifying at least one of the jets as originating from a b quark. The analyzed data correspond to 3.6 fb-1 of pp collisions at √s = 1.96 TeV acquired by D0 in Run II of the Fermilab Tevatron Collider. The combination of the e + jets and µ + jets channels yields ∆m =0.8 ± 1,8 stat ± 0.5(syst) GeV, which is in agreement with the standard model expectation of no mass difference.

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