Searching for SM-like heavy new quarks at the LHC

This thesis describes the search performed with the ATLAS detector for heavy quarks (denoted as Q) in the Q\={Q} $\rightarrow$ WqWq channel where one W boson decays leptonically and the other hadronically. Final state of this processes is four jets, one lepton and missing transverse energy. %In this search,final state jets are forced to be light jets. The analysis is based on an integrated luminosity of $20fb^{-1}$ data collected during the 2012 from proton-proton collisions at a centre-of-mass energy of 8 TeV. No significant excess of events above the Standard Model expectation is observed and lower limit on the Q quark mass has been set at 519 GeV with 95\% confidence level.