Beyond the Standard Model Higgs sectors

Thesis

Although the experimentally detected 125 GeV spin-0 resonance has properties very close to the one predicted by the Standard Model, it is still possible that the Higgs sector in nature is not SM-like. In this work we will discuss two projects investigating the experimental validity of THDM (Two Higgs Doublet Model) and THDM+S models.

In the first project we demonstrate that the peak (2.3 σ) at 95 GeV as recently seen by CMS collaboration in the di-photon final state can be explained within the type-I THDM by means of fermiophobic CP-even Higgs boson H. In this context we discuss the other Higgs anomalies such as LEP excess in Higgsstrahlung and observation of enhanced rates in tt¯h at the LHC, showing that parameters capable of explaining the CMS di-photon excess can address these deviations as well while at the same time being compatible with LHC Run-I Higgs signal strength measurements.

In the second project we investigate experimental bounds on the exotic Higgs decays into the pair of light pseudoscalars devoting special attention to the mass regions of [3,4] GeV and [9,11] GeV where the pseudoscalar can mix with the QCD bound states η_c and η_b respectively. We find that mixing effects can modify the total decay width of the pseudoscalar and therefore have an impact on the derived bounds. We present exclusion limits on μ_hBR(h → aa) and μ_h BR(h → aZ) at a 95% C.L. in the framework of THDM+S model in order to facilitate the comparison with the recent results by the CMS collaboration.

Authors: Malinauskas, A

• DOI: 10.5287/ora-2rqgyjvvg
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: standard model; two higgs doublet model; BSM; THDM
• Subjects: Higgs bosons; Beyond the Standard Model