PhD defence by Lars Egholm Pedersen – University of Copenhagen

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PhD defence by Lars Egholm Pedersen

Abstract:

A series of studies are presented of the Higgs-like resonance that was discovered in July of 2012.

Alternative spin and parity models are compared to the Standard Model Higgs mainly through the ZZ*->4l decay channel.

Spin-2 models are described as graviton-like particles where several assumptions on the boson coupling to the QCD sector are tested.
The Standard Model is found to be favoured over all alternative models and
notably the spin-2 universal couplings model is assigned a CLs value of 0.0009.
The spin-0 boson coupling to the heavy vector bosons is described in an effective field theory approach with three components, the Standard Model and a CP-even BSM and CP-odd sector. Assuming only one coupling to be present at a time, the Standard Model is tested against the CP-even BSM and CP-odd model. The Standard Model is favoured in data and the two alternate models are assigned CLs values of 0.10 (CP-even) and 0.054 (CP-odd).

The analysis is extended by allowing a mixture of the three spin-0 components, first assuming only one BSM coupling to be present at a time. Discriminative power between models is obtained in a Matrix-Element Observable approach. The H->ZZ*->4l channel is combined with the H->WW*->enumunu analysis. The effective BSM cross section contributions to the resonance is found to be limited to the ranges:
-0.16 < f_g2 < 0.12 -0.41 < f_g4  < 0.090 at 95% confidence level.