25-30 September 2011
Sant Feliu de Guixols, Spain
Europe/Madrid timezone

The measurement of the top quark charge in the ATLAS experiment

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Sant Feliu de Guixols, Spain

Sant Feliu de Guixols, Spain


Pavol Federic (Bratislava University)


We present a measurement of the electric charge of the top quark in the lepton+jets final states using 0.70/fb of data accumulated in the ATLAS experiment at a center of mass energy of 7 TeV. The top quark charge measurement is based on reconstructing the charges of the top quark decay products. While we determined the charge of the W boson through its leptonic decay, the b-quark charge is not directly measurable. However we use two methods to determine b-quark charge. The first is based on a correlation between the charge of the b-quark and a weighted sum of the charges of the hadrons produced in the b-quark hadronisation process (track charge weighting technique). The second method uses semileptonic B-hadrons decays. In this case the sign of the lepton arising from the semileptonic decay defines the sign of the b-quark (soft lepton technique). The results were compared with expectations for the Standard Model top quark and for a "top-like" quark with an exotic charge of -4/3e. The exotic scenario is excluded at more than five standard deviations confidence level using both methods of determining the b-jet charge.

Primary authors

Pavol Federic (Bratislava University) Zdenek Dolezal (Charles University (CZ))

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