Karlsruhe 2011 – scientific programme

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T: Fachverband Teilchenphysik

T 41: Top-Quarks: Eigenschaften I

T 41.5: Talk

Thursday, March 31, 2011, 17:45–18:00, 30.41: 005

Direct Measurement of the Mass Difference Between Top and Antitop Quarks — •Oleg Brandt, Carsten Hensel, Jason Mansour, Jörg Meyer, Arnulf Quadt, and Elizaveta Shabalina — II. Physikalisches Institut, U. Göttingen

We present a direct measurement of the mass difference between top and antitop quarks (Δ M) in lepton+jets tt final states using the “Matrix Element” method developed at the D0 experiment. The purity of the lepton+jets sample is enhanced for tt events by applying a neural-network-based b-jet identification technique. 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 Δ M=x.x± x.x (stat)± x.x (syst) GeV, which is in agreement with the standard model prediction of no mass difference.