\contentsline {section}{\numberline {1}Introduction}{2}
\contentsline {section}{\numberline {2}Data and Simulation Samples}{3}
\contentsline {section}{\numberline {3}Lepton Reconstruction and Identification}{5}
\contentsline {section}{\numberline {4}Event Selection Optimization}{6}
\contentsline {subsection}{\numberline {4.1}Optimization for the four muons final state}{6}
\contentsline {subsection}{\numberline {4.2}Optimization for channels with Electrons}{8}
\contentsline {section}{\numberline {5}Event Selection}{11}
\contentsline {section}{\numberline {6}Trigger Considerations}{12}
\contentsline {section}{\numberline {7}Data based study of the lepton selection criteria}{13}
\contentsline {subsection}{\numberline {7.1}Efficiency for signal-like leptons}{13}
\contentsline {subsubsection}{\numberline {7.1.1}$Z\rightarrow ee$}{13}
\contentsline {subsubsection}{\numberline {7.1.2}$Z\rightarrow \mu \mu $}{13}
\contentsline {subsection}{\numberline {7.2}Efficiency for background-like leptons}{13}
\contentsline {subsubsection}{\numberline {7.2.1}$Z+e$}{13}
\contentsline {subsubsection}{\numberline {7.2.2}$Z+\mu $}{13}
\contentsline {section}{\numberline {8}Background Estimation}{14}
\contentsline {subsection}{\numberline {8.1}Data driven cross-checks of the $t\mathaccentV {bar}016{t}$ background}{14}
\contentsline {subsection}{\numberline {8.2}Estimate of the $Z+\mu \mu $ background}{14}
\contentsline {subsubsection}{\numberline {8.2.1}Efficiency estimation for muons in Jets}{14}
\contentsline {subsection}{\numberline {8.3}Estimate of the $Z+ee$ background}{17}
\contentsline {subsection}{\numberline {8.4}Data driven cross-checks of the QCD background}{17}
\contentsline {subsection}{\numberline {8.5}Background shapes}{17}
\contentsline {section}{\numberline {9}Results of Event Selection}{20}
\contentsline {section}{\numberline {10}Systematic Uncertainties}{21}
\contentsline {section}{\numberline {11}Exlusion limits and $p$-values}{22}
\contentsline {section}{\numberline {12}Conclusions}{23}
\contentsline {section}{Appendices}{24}