Guimaraes da Costa, JoaoSpearman, William2014-10-212014-10-212014Spearman, William R. 2014. Measurement of the mass and natural width of the Higgs boson in the H to ZZ to 4l decay channel with the ATLAS detector. Doctoral dissertation, Harvard University.http://dissertations.umi.com/gsas.harvard.inactive:11773http://nrs.harvard.edu/urn-3:HUL.InstRepos:13070058This thesis presents a measurement of the mass, natural width, and signal strength, defined as the yield normalized to the Standard Model prediction, of the Higgs boson in the \(H \rightarrow ZZ^{(*)} \rightarrow 4l\) decay channel using an approach which utilizes event-by-event detector response information. The measurement is performed on p-p collision data recorded by the ATLAS experiment at the CERN Large Hadron Collider. The data corresponds to an integrated luminosity of \(25 fb^{-1}\) with center-of-mass energies of 7 TeV and 8 TeV. The measured mass of the Higgs boson is \(m_H = 124.57_{-0.43}^{+0.48} GeV\). The signal strength was estimated at \(\mu = 1.76_{-0.37}^{+0.46}\). Finally, the natural width of the Higgs was determined to be < 2.6 GeV with 95% confidence. The event-by-event approach used in this analysis involves the parameterization of the behavior of single leptons in the ATLAS detector and the convolution of a mass response with the Higgs truth distribution to derive the reconstruction level signal model.en-USPhysicsParticle physicsATLASCERNHiggs bosonHiggs massHiggs widthParticle physicsThesis or Dissertation2014-10-21