Higgs couplings to light quarks
IDPASC Portugal - PHD Programme 2019
2019 / 2020
Experimental Particle Physics
Instituto Superior Técnico
Laboratório de Instrumentação e Física Experimental de Partículas
The couplings of the Higgs boson to the third fermion family have been recently detected. During 2018, ATLAS and CMS have reported the observation of the couplings to the heaviest fermions, the top and bottom quarks. The important step that follows is then to investigate the couplings to the lighter quarks. This goal is nonetheless challenging, for two reasons: as the Higgs couples in proportion to the particle’s mass, the relevant processes are rarer; also, there are backgrounds (QCD) that result in quark-pair production considerably more abundantly than Higgs decays to quark pairs. There is an alternative approach, however. The quark-antiquark pairs originating from the Higgs decay may bind together (thus forming a meson state). Experimentally, this gives rise to a striking, clean signature: an energetic photon back-to-back to a dilepton resonance. In this thesis project the student will investigate such exclusive decays of the Higgs boson using data just collected by CMS during LHC Run2. The motivation for the work is two-fold: experimentally constrain the Higgs-quark couplings and detect the effects of potential new physics that may be revealed in these sensitive processes.