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# Experimental study of the properties of the Higgs boson

Mudd, Richard David (2016)
Ph.D. thesis, University of Birmingham.

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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: Ph.D. thesis. Nikolopoulos, Konstantinos and Newman, Paul Colleges (2008 onwards) > College of Engineering & Physical Sciences School of Physics and Astronomy, Particle Physics Group QC Physics University of Birmingham 6761
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