Dark matter searches in two-lepton final states with missing transverse energy using ATLAS open data

While the Standard Model of particle physics encompasses our current understanding of fundamental particles and interactions, it leaves several open questions, including the nature of dark matter. This thesis presents searches for dark matter candidates using ATLAS Open Data for education with two theoretical frameworks: supersymmetric chargino-neutralino production, and semi-dark Higgs boson decays, both focusing on two-lepton final states and missing transverse energy. The analyses are performed using proton-proton collision data collected by the ATLAS detector at 13 TeV corresponding to 36 fb−1. Event selection criteria and statistical methods are applied to distinguish potential signals from the Standard Model background. No statistically significant excess above the expected background is observed, and the results are consistent with Standard Model expectations. The supersymmetric search sets 95% confidence level upper limit on chargino-neutralino production, excluding masses up to approximately 580 GeV for a massless neutralino and a 95% confidence level upper limit of 0.12 fb on the visible cross section. For the semi-dark Higgs boson decay search, a 95% confidence level upper limit of 3.26 fb is set on the visible cross section. Additionally, this work develops complementary educational Jupyter notebooks designed to bridge the gap between particle physics research and outreach. These notebooks guide users through key aspects of the analyses, enabling students to reproduce select results. By combining research analyses with educational materials, this thesis contributes to both ongoing dark matter searches and outreach and education in particle physics.