Search for Exotic Top Partners with the CMS Experiment

This note presents a study of searches for two exotic particles - a heavy top quark partner with a fractional charge of 5/3, $T_{5/3}$, and its partner, the heavy $B$ quark with charge -1/3. These particles decay to a top quark and a $W$ boson, leading to very busy events with multi-leptons and multi-jets. Processes where same-sign dileptons are produced are considered. The backgrounds are predominantly from $t\overline t$, QCD multi-jets, $Z$+jets, $t\overline t WW$, $t\overline t W$ and multiple-$W$+jets production. The study shows that it is possible to observe these exotic particles during the early running period of the Large Hadron Collider. Approximately $80$~pb$^{-1}$ of data at $\sqrt{s} =10$~TeV would be needed to exclude such heavy new particles up to masses of about 400~GeV and $115$~pb$^{-1}$ would be necessary for a $5\sigma$ observation at the same mass. With $340$~pb$^{-1}$ of integrated luminosity at $\sqrt{s} =10$~TeV, masses of up to 500~GeV can be excluded. At $\sqrt{s} =14$~TeV only about 150~pb$^{-1}$ would be needed for a $5\sigma$ observation at a mass of 500~GeV.