Doctoral Dissertation Open Access

Global Interpretation of ττ Events in the Context of the Standard Model and Beyond

Gottmann, Artur

Thesis supervisor(s)

Wolf, Roger; Quast, Günter

The nature of interactions between elementary particles nowadays is successfully described by the Standard Model of particle physics (SM), with predictions covering a wide range of observed phenomena, including the existence of the Higgs boson, discovered by two independent experiments, ATLAS and CMS. Measurements of its properties are compatible with the SM, however, there is strong belief to consider it as part of an extended Higgs sector, motivating searches for additional heavy Higgs bosons.
Until now, measurements of properties of the observed Higgs boson, and their interpretation in models beyond the Standard Model (BSM) in the framework of effective field theories, are performed independently from searches for additional heavy Higgs bosons. The main topic of this thesis is to perform a unification of the two analysis approaches on the example of the H→ττ decay channel into one, consistent, global interpretation of ττ events, based on Run 2 CMS data at a centre of mass energy of 13 TeV and comprising 137 fb-1.
At first, a measurement of signal strengths of the observed Higgs boson results in an observed (expected) significance of  6.1 (5.0)σ for gluon fusion and 1.9 (3.8)σ for vector boson fusion production channels of the Higgs boson to ensure a good expected sensitivity to the observed Higgs boson. Then, a classic search for additional heavy Higgs bosons is performed, superseeding the current CMS results based on data collected in 2016. In the last step, the two analyses are combined into a consistent interpretation of ττ events in the framework of BSM benchmark scenarios to demonstrate an increased sensitivity to deviations in scenario predictions for the BSM Higgs boson to be compatible with the observed Higgs boson, leading to an increased exclusion power on BSM benchmark scenarios.

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