Measurement of the Inclusive $Z \to ee$ Production Cross Section in Proton-Proton Collisions at $\sqrt{s}$ = 7TeV and $Z \to ee$ Decays as Standard Candles for Luminosity at the Large Hadron Collider

This thesis comprises a precision cross section measurement of inclusive $Z \to ee$ production in proton-proton collisions provided by the Large Hadron Collider (LHC) at a center-of-mass energy of $\sqrt{s}$=7TeV. The data was collected by the Compact Muon Solenoid (CMS) detector near Geneva, Switzerland during the year of 2010 and corresponds to an integrated luminosity of $\intmathcal{L}dt = 35.9pb^{-1}$. Electronic decays of $Z$ bosons provide one of the first electroweak measurements at the LHC, making this analysis a benchmark of physics performance after the first year of CMS detector and LHC machine operations. It is the first data-driven, systematic uncertainty limited, inclusive $Z \to ee$ production cross section measurement performed at $\sqrt{s}$=7TeV. \\begin{equation} \\sigma(pp \\to Z+X) \\times \\mathcal{B}( Z \\to ee ) = 997 pm 11 \\mathrm{(stat)} pm 19 \\mathrm{(syst)} pm 40 \\mathrm{(lumi)} \\textrm{ pb} \\end{equation} which agrees with the theoretical prediction of: \\begin{equation} \\sigma(pp \\to Z+X) \\times \\mathcal{B}( Z \\to ee )_{ \\textrm{scriptsize{NNLO Theory}}} = 970 pm 40 \\textrm{ pb} \\end{equation} calculated to next-to-next-to-leading-order in QCD using recent parton distribution functions. Leveraging $Z \\to ee$ decays as ``standard candles'' for measuring the luminosity at the LHC is examined; they are produced copiously at the LHC, are well understood, and have clean detector signatures. Thus the consistency of the measurement with the theoretical prediction suggests inverting the result to instead use the $Z \\to ee$ signal yield to calibrate the luminosity.