Exclusion of an Exotic Top Quark with -4/3 Electric Charge Using Soft Lepton Tagging

Abstract

We present a measurement of the electric charge of the top quark using $\ppbar$ collisions corresponding to an integrated luminosity of 2.7~fb${}^{-1}$ at the CDF II detector. We reconstruct $\ttbar$ events in the lepton+jets final state and use kinematic information to determine which $b$-jet is associated with the leptonically- or hadronically-decaying $t$-quark. Soft lepton taggers are used to determine the $b$-jet flavor. Along with the charge of the $W$ boson decay lepton, this information permits the reconstruction of the top quark's electric charge. Out of 45 reconstructed events with $2.4\pm 0.8$ expected background events, 29 are reconstructed as $\ttbar$ with the standard model $+$2/3 charge, whereas 16 are reconstructed as $\ttbar$ with an exotic $-4/3$ charge. This is consistent with the standard model and excludes the exotic scenario at 95\% confidence level. This is the strongest exclusion of the exotic charge scenario and the first to use soft leptons for this purpose.

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• Exclusion of exotic top-like quarks with -4/3 electric charge using jet-charge tagging in single-lepton ttbar events at CDF
• Precision measurements of the top quark mass from the Tevatron in the pre-LHC era
• Top Quark Physics at the Tevatron
• Observation of Single Top Quark Production
• Neutral meson mixing induced by box diagrams in the 3-3-1 model with heavy leptons
• Top Quark Physics at the Tevatron
• A Model with Chiral Quarks of Electric Charges -4/3 and 5/3