We present a measurement of the electric charge of the top quark using $p\overline{p}$ collisions corresponding to an integrated luminosity of $2.7{\mathrm{fb}}^{-1}$ at the CDF II detector. We reconstruct $t\overline{t}$ events in the $\mathrm{\text{lepton}}+\mathrm{\text{jets}}$ final state. We use soft lepton taggers to determine the flavor of the $b$ jets, which we use to reconstruct the top quark’s electric charge and exclude an exotic top quark with $-4/3$ charge at 95% confidence level. This is the strongest exclusion of the exotic charge scenario and the first to use soft leptons for this purpose.

• Received 24 June 2010

DOI:https://doi.org/10.1103/PhysRevLett.105.101801