New tools to measure the top quark Yukawa coupling and explore non-standard Higgs models
IDPASC Portugal - PHD Programme 2016
2016 / 2017
Theoretical Particle Physics | Experimental Particle Physics
Faculdade de Ciências - Universidade de Lisboa
Laboratório de Instrumentação e Física Experimental de Partículas
The Higgs coupling to top quarks is expected to be the largest Yukawa coupling in the Standard Model (SM) of particle physics. Its measurement is a priority of the ATLAS Higgs programme for the LHC run 2. The most promising production channel allowing a direct measurement of this coupling is the associated Higgs production with a top-quark pair, ttH. The goal of the proposed project is twofold, encompassing both experimental and phenomenological studies. On the experimental side, the goal is to observe ttH production in proton-proton collisions recorded by the ATLAS experiment during run 2 of the LHC. This is a very challenging analysis; to make it possible we propose to use a new analysis technique being developed by the supervisors and other collaborators. This technique exploits differences in angular correlations found in ttH and in the dominant irreducible background, ttbb, which arise from the different spins of the Higgs boson and the gluon. The proposed technique has the potential to be extended to other channels and most notably to provide sensitivity to the Higgs CP quantum numbers. The further development and extension of the technique will constitute the phenomenological part of the project. With these tools, the student will contribute to the understanding of crucial properties of the Higgs boson, which will have a strong impact on exploring models of new physics such as the two-Higgs doublet model.