Search for beyond Standard Model physics with high-pt leptons

This thesis covers four different topics related to the physics analysis in the ATLAS experiment that uses proton-proton collisions data provided by the Large Hadron Collider. The first topic is focused on the numerical simulation of the Transition Radiation Tracker which is one of the ATLAS tracking detectors. The implementation of the alternative Argon based gas mixtures used in the drift tubes is described. A performance study with focus on the hit and track parameters with respect to the gas mixture is discussed as well. The second topic is related to the ATLAS luminosity monitor called LUCID. A number of studies are presented from the design phase of the detector and of its calibration system as well as detector operation, the performance and luminosity measurements. The two last topics are analyses that searches for beyond Standard Model physics with the ATLAS detector. The first search presented in the thesis is done in a final state with same-sign electron pairs using the data collected at a center of mass energy of √s = 8 TeV. No significant excess above the predictions of the Standard Model is observed. Limits on the fiducial cross section for new physics as a function of the invariant mass of electron pairs have been set as well as mass limits for doubly charged Higgs models. The second analysis is focused on a search for a new heavy charged gauge boson in the final state with one lepton and missing transverse momentum at √s = 13 TeV. Since no significant deviation from the Standard Model is observed, limits on a new heavy charged gauge boson-mass are set.