Search for squarks and gluinos in final state with jets, missing transverse momentum and boosted W bosons with the ATLAS experiment

At the time of this writing, Supersymmetry is the most discussed extension of the Standard Model. A significant part of the supersymmetric parameter space can be explored with accelerators like the Large Hadron Colider (LHC) at CERN, which provides proton collisions for the ATLAS detector. If Supersymmetry is realized at the weak scale, one of the most promising production channels at the LHC is the direct production of squark and gluino pairs. The search for such events with no lepton, large missing transverse momentum and large transverse momentum of the jets is presented in this thesis. Experimental limits on cross-sections of squark and gluino pair production are interpreted in Simplified models with various assumptions on the masses of these particles. Reconstruction of specific particles, like $W$-bosons or $\tau$-leptons, can increase the sensitivity of the analysis in two ways: as a veto in case the desired particle is not in the final state of the signal model, or as a requirement in the opposite case. A study on the $W$-boson tagging and its usage in both these cases, that lead to published results, is described in this thesis. Alternative approaches to the $W$-boson reconstruction, such as using the substructure of jets, are discussed as well. Attention is also given to the alternative fit methods of the peak in the invariant mass of the $W$.