Search for new T′ particles in final states with large jet multiplicities and missing transverse energy in pp̄ collisions at √s=1.96TeV

We present a search for a new particle T' decaying to a top quark via T' = t + X, where X goes undetected. We use a data sample corresponding to 5.7 fb-1 of integrated luminosity of pp collisions with √s = 1.96 TeV, collected at Fermilab Tevatron by the CDF II detector. Our search for pair production of T' is focused on the hadronic decay channel, pp = T'T' = tt+XX=bqqbqq + XX. We interpret our results in terms of a model where T' is an exotic fourth generation quark and X is a dark matter particle. The data are consistent with standard model expectations. We set a limit on the generic production of T'T' = tt =+ XX, excluding the fourth generation exotic quarks T' at 95% confidence level up to mT` = 400 GeV/c2 for mX ≤ 70 GeV/c2.