Searches for fourth generation top quark in dilepton channel at ATLAS

A fourth generation of quarks is a natural and powerful extension to the Standard Model. It supports heavier Higgs models, provides additional CP Violation for $B_s$ decays, and addresses numerous other theoretical and experimental questions. We present a search for pair-produced heavy up-type fourth generation quarks, $t'\bar{t'} \to W^+ W^- b\bar{b}$, with the ATLAS detector at the LHC. We examine events where both $W$ bosons decay leptonically, and we reconstruct the $t'$ invariant mass using a collinear approximation to deduce the missing neutrino information from the lepton directions and $E_{\mathrm{T}}^{\mathrm{miss}}$ of each event. Our search encompasses a total recorded luminosity of 38 $pb^{-1}$ of pp collisions at center-of-mass energy of $\sqrt{s} = 7$ TeV.