We study the detection of the $t^{\prime }$ of a fourth family during the early running of LHC with 7 TeV collision energy and $1{\mathrm{fb}}^{-1}$ integrated luminosity. By the use of a neural network we show that it is feasible to search for the $t^{\prime }$ 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 $10{\mathrm{fb}}^{-1}$. In both cases the search for a fourth family quark doublet can be significantly enhanced if one incorporates the contribution that the $b^{\prime }$ can make to a $t^{\prime }$-like signal. Thus, the bound on the mass of a degenerate quark doublet should be stronger than the bounds obtained by treating $t^{\prime }$ and $b^{\prime }$ in isolation.

• Received 8 March 2011

DOI:https://doi.org/10.1103/PhysRevD.83.114031