Searches for thet′of a fourth family

Abstract

We study the detection of the ${t}^{\ensuremath{'}}$ of a fourth family during the early running of LHC with 7 TeV collision energy and $1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ integrated luminosity. By the use of a neural network we show that it is feasible to search for the ${t}^{\ensuremath{'}}$ even with a mass close to the unitarity upper bound, which is in the 500 to 600 GeV range. We also present results for the Tevatron with $10\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. In both cases the search for a fourth family quark doublet can be significantly enhanced if one incorporates the contribution that the ${b}^{\ensuremath{'}}$ can make to a ${t}^{\ensuremath{'}}$-like signal. Thus, the bound on the mass of a degenerate quark doublet should be stronger than the bounds obtained by treating ${t}^{\ensuremath{'}}$ and ${b}^{\ensuremath{'}}$ in isolation.