This thesis presents two production cross-section measurements of pairs of massive bosons using ï¬nal states with leptons, made with the ATLAS detector at the Large Hadron Collider. The ï¬rst measurement, performed using data collected in 2012 at center-of-mass energy ' s = 8 TeV, is the ï¬rst ï¬ducial and diï¬erential cross-section measurement of the production of the Higgs Boson when it decays to four charged leptons (electrons or muons). The second measurement is the ï¬rst ï¬ducial and inclusive production cross-section measurement of WZ pairs at center-of-mass energy ' s = 13 TeV using ï¬nal states with three charged leptons. A signiï¬cant portion of the thesis focuses on the methods used to identify electrons from massive boson decay-important for many ï¬agship measurements-and on assessing the eï¬ciency of these particle identiï¬cation techniques. The chapter discussing the WZ pair cross-section measurement provides a detailed example of an estimate of lepton background in the context of an analysis with three leptons in the ï¬nal state. | Physics With Electrons In The Atlas Detector by Kurt Brendlinger, Hardcover | Indigo Chapters