A search for neutral high-mass Higgs bosons decaying into pairs of hadronically decaying tau leptons in 13 TeV collisions recorded by the ATLAS detector

Thesis

This thesis outlines the search for neutral Higgs bosons in a mass range of m_H/A = 200 GeV − 1.2 TeV, decaying to a pair of hadronically decaying tau leptons. The search is performed using √s = 13 TeV proton-proton collision data, corresponding to an integrated luminosity of 3.21 fb⁻¹, recorded by the ATLAS detector. No excess over the predicted Standard Model background is observed and upper limits are placed on the production cross section times branching fraction as a function of the mass of the scalar resonance. When combined with the results of the analysis where one of the tau leptons decays to either a muon or electron, the 95% confidence level upper limit on the cross section times branching fraction ranges from 1.4 pb at m_H/A = 200 GeV to 0.025 pb at m_H/A = 1.2 TeV for a scalar boson produced via gluon-gluon fusion, and 1.6 pb at m_H/A = 200 GeV to 0.028 pb at m_H/A = 1.2 TeV for a scalar boson produced via b-associated production. The results are interpreted in the Minimal Supersymmetric extension to the Standard Model (MSSM) as a limit on the value of tanβ, as a function of the mass of the neutral CP-odd MSSM Higgs boson. In the mmod+ scenario, the 95% confidence level upper limit is tanβ < 7.6 for m_A = 200 GeV, and tanβ < 47 for m_A = 1 TeV. For the mass range m_A > 500 GeV, the upper limit on tanβ is improved in comparison to previous ATLAS searches.

Authors: Pickering, M

• DOI: 10.5287/ora-mqe2pnqxr
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: tau lepton; The ATLAS experiment; Higgs boson; Large Hadron Collider; supersymmetry; physics; particle physics
• Subjects: Particles (Nuclear physics)