Searches for the $t^\prime$ of a fourth family

TL;DR

This paper demonstrates the feasibility of detecting a hypothetical fourth-family top quark ($t'$) at LHC and Tevatron using neural networks, suggesting improved search strategies and stronger mass bounds.

Contribution

It introduces a neural network-based method for $t'$ detection and shows how considering $b'$ contributions enhances search sensitivity and mass bounds.

Findings

Feasibility of $t'$ detection near 500-600 GeV at LHC and Tevatron.

Neural networks improve search sensitivity for fourth-family quarks.

Incorporating $b'$ contributions strengthens mass bounds on degenerate quark doublets.

Abstract

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 fb$^{-1}$ integrated luminosity. By use of a neural network we show that it is feasible to search for the $t'$ 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 $10 \,\, \textrm{fb}^{-1}$. In both cases the search for a fourth family quark doublet can be significantly enhanced if one incorporates the contribution that the $b'$ can make to a $t'$-like signal. Thus the bound on the mass of a degenerate quark doublet should be stronger than the bounds obtained by treating $t'$ and $b'$ in isolation.