Searches for beyond Standard Model physics with same-sign dileptons

An introduction into the theory and experimental background of particle physics and the ATLAS detector is given. The transition radiation tracker (TRT) which is vital to the particle tracking and identification is then described giving particular creedence to the calibration. The automation of this calibration is explained. The second half of this thesis and the central part dwells on the analyses searching for beyond Standard model physics at the ATLAS detector using same-sign dilepton pairs (e±e±, e±μ±, μ±μ±) during both the 7 TeV and 8 TeV data taking periods at the Large Hadron Collider (LHC). In both searches no significant excess from the standard model (SM) was seen. Limits were set on the fiducial cross-section for new physics as a function of invariant mass. Exclusion limits are also derived for a specific model of doubly charged higgs boson production and are seen to improve from the 7 TeV analysis to the 8 TeV analysis.