Recherche d'un nouveau boson massif $W$' se désintégrant en un quark top et un quark $b$ avec le détecteur ATLAS au LHC

The main goal of this thesis is the search for new charged massive gauge bosons, $W$' that decay to a top quark and a bottom quark leading to a final state with a charged lepton, neutrino, and two $b$ quarks. The search is performed with the ATLAS detector at the LHC using data collected in proton–proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV and corresponding to an integrated luminosity of 36.1 fb$^{-1}$. This analysis covers resonance masses between 0.5 and 5.0 TeV and considers right-handed $W$' bosons, $W$'$_{R}$. No significant deviation from the Standard Model expectation is observed and upper limits are set on the cross section times branching ratio and the $W$' boson effective couplings as a function of the $W$' boson mass. $W$'_R bosons with coupling equal to the Standard Model weak coupling constant. Masses below 3.15 TeV are excluded at the 95% confidence level. This search is also combined with that for $W$'->tb in the fully hadronic final state. Using the combined searches, right-handed W' bosons with masses below 3.25 TeV are excluded at the 95% confidence level. This thesis includes also the work carried out to integrate into the ATLAS simulation code the signal processing of the hadronic Calorimeter (TileCal) front-end readout called FATALIC. FATALIC was developed at Laboratoire de Physique de Clermont-Ferrand (LPC) and proposed for the High Luminosity (HL) phase LHC upgrade. Taking into account the expected electronic noise, the performances obtained on the energy measurement are presented for two relevant cells and for different values of pileup noise.