Search for Production of Heavy Particles Decaying to Top Quarks and Invisible Particles in pp[over-bar] Collisions at [sqrt]s=1.96 TeV

Abstract

We present a search for a new particle T′ decaying to top quark via T′-->t+X, where X is an invisible particle. In a data sample with 4.8 fb[superscript -1] of integrated luminosity collected by the CDF II detector at Fermilab in pp[over-bar] collisions with [sqrt]s=1.96 TeV, we search for pair production of T′ in the lepton+jets channel, pp[over-bar] -->tt[over-bar] +X+X-->ℓνbqq′b+X+X. We interpret our results primarily in terms of a model where T′ are exotic fourth generation quarks and X are dark matter particles. Current direct and indirect bounds on such exotic quarks restrict their masses to be between 300 and 600 GeV/c[superscript 2], the dark matter particle mass being anywhere below mT′. The data are consistent with standard model expectations, and we set 95% confidence level limits on the generic production of T′T[over-bar] ′-->tt[over-bar] +X+X. For the dark matter model we exclude T′ at 95% confidence level up to mT′=360 GeV/c[superscript 2] for mX[less than or equal to]100 GeV/c[superscript 2].