Measurement of the Electric Charge of the Top Quark in boldsymbol{tbar{t}} Events

We present a measurement of the electric charge of top quarks using $t\bar{t}$ events produced in $p\bar{p}$ collisions at the Tevatron. The analysis is based on fully reconstructed $t\bar{t}$ pairs in lepton+jets final states. Using data corresponding to 5.3 $\rm fb^{-1}$ of integrated luminosity, we exclude the hypothesis that the top quark has a charge of $Q=-4/3\,e$ at a significance greater than 5 standard deviations. We also place an upper limit of 0.46 on the fraction of such quarks that can be present in an admixture with the standard model top quarks ($Q=+2/3\,e$) at a 95\% confidence level.