Measuring the Higgs boson mass using event-by-event uncertainties

The thesis presents a measurement of the properties of the Higgs particle, performed by using the data collected by the ATLAS experiment in 2011 and 2012. The measurement is performed by using a three-dimensional model based on analytic functions to describe the signal produced by the Higgs boson decays into four leptons. The model includes the information provided by the uncertainty measured event-by-event on the four-lepton invariant mass. A maximum likelihood fit is used to obtain an unbiased estimate of the mass, the signal strength and the decay amplitude of the Higgs particle. The best estimation of the Higgs boson mass results to be: $124.52^{+0.48}_{-0.49}(\text{stat.})\pm0.08(\text{syst.})\text{GeV}$