Doubly Charged Higgs Signal with Same-Sign Tau-inclusive Dilepton Final States

Abstract: Abstract The current Standard Model of particle physics contains few interactions resulting in a final state with two leptons with the same charge. Any observation of an excess of such same-sign dileptons would be an indication of new physics processes, making it a useful channel when searching for exotic physics. This thesis presents three projects conducted within the ATLAS Same-Sign Dilepton group for extending their previous same-sign dilepton analysis to include \tau-leptons. Including the heaviest lepton in the analysis gives access to more statistics from the available data and allows probing of theories with mass-dependent lepton coupling to, for example, the doubly charged Higgs particle. To this end, Monte Carlo signal samples with pair production of doubly charged Higgs decaying into two same-sign dileptons was requested, and the resulting signal samples and the method for generating them will be presented. A filter able to generate a specific \tau-lepton final state in event generation was created, and validation of its function is shown. Finally, a small proof-of-concept study of \tau-lepton charge flip estimation using a data-driven likelihood method will be presented.