A search for the production of heavy partners of the top quark with charge 5/3 is performed in events with a pair of same-sign leptons. The data sample corresponds to an integrated luminosity of 19.5 fb−1 and was collected at s√=8 TeV by the CMS experiment. No significant excess is observed in the data above the expected background, and the existence of top-quark partners with masses below 800 GeV is excluded at a 95% confidence level, assuming they decay exclusively to tW. This is the first limit on these particles from the LHC, and it is significantly more restrictive than previous limits.
Stringer, Robert W., Phillip S. Baringer, Alice Bean, Gabriele Benelli, and Stephen J. Sanders. "Search for Top-Quark Partners with Charge 5/3 in the Same-Sign Dilepton Final State." Physical Review Letters 112.17 (2014). http://dx.doi.org/10.1103/PhysRevLett.112.171801