Experimental study of the properties of the Higgs boson

Mudd, Richard David (2016). Experimental study of the properties of the Higgs boson. University of Birmingham. Ph.D.

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Abstract

Measurements of Higgs boson production and decay rates are presented using the proton-proton collision data collected by the ATLAS experiment during LHC Run I, corresponding to 4.5 fb\(^-\)\(^1\) at 7 TeV and 20.3 fb\(^-\)\(^1\) at 8 TeV. Under certain assumptions, the coupling strengths of the Higgs boson to Standard Model particles are also probed.

The H -> ZZ\(^(\)\(^*\)\(^)\)\(_-\)\(_>\) 4I final state, where I = e, mu, is discussed, and is observed with a significance corresponding to 8.1 standard deviations. The Higgs boson production rate, relative to the Standard Model prediction, is measured to be mu = 1.44\(^+\)\(^0\)\(^.\)\(^4\)\(^0\)\(_-\)\(_0\)\(_.\)\(_3\)\(_3\) at the ATLAS best-fit value for the measurement of the Higgs boson mass, m\(_H\) = 125.36 GeV.

The various Higgs boson production and decay modes studied by the ATLAS experiment are also combined. The couplings of the Higgs boson are probed in a number of benchmark models, where a good agreement with the Standard Model prediction is observed for each model considered. The Higgs boson coupling measurements are also used to place constraints on a number of beyond the Standard Model theories, and are combined with direct searches for invisible Higgs boson decays to place a limit on the Higgs boson branching ratio to invisible final states.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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