Exclusion limits at 95% CL on the pp → b′ anti-b′ production cross-section (σ). The solid line represents the observed limits, while the dotted line represents the limits expected for the available data, assuming the presence of Standard Model processes alone. A comparison with the production cross-sections excludes b′ masses Mb′ < 611 GeV/c2 at 95% CL for a 100% b′ → tW decay branching fraction.
Results are presented from a search for heavy bottom-like quarks, produced in pairs in pp collisions at √s = 7 TeV, undertaken with the CMS experiment at the LHC. The b′ quarks are assumed to decay exclusively to a top quark and a W boson (tW). The b′ anti-b′ to t W+ anti-t W− process can be identified by its distinctive signatures of three leptons or two leptons of same charge, and at least one b-quark jet. Using a data sample corresponding to an integrated luminosity of 4.9 fb−1 (inverse femtobarns), observed events are compared to the Standard Model background predictions, and the existence of b′ quarks having masses below 611 GeV/c2 is excluded at 95% confidence level.