Search for decays of the Higgs Boson into a Z Boson and a light hadronically decaying resonance

Wu, Chonghao (2024). Search for decays of the Higgs Boson into a Z Boson and a light hadronically decaying resonance. University of Birmingham. Ph.D.

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Abstract

The work for this thesis was conducted within the ATLAS experiment. Initially, a noise study of the trigger system of ATLAS experiment was undertaken. This included the searching for noisy trigger towers and adjusting the noise thresholds for the new trigger component eFEX.
Subsequently, a search for Higgs boson decays to a Z boson and a light resonance a is performed, using 140~fb^{-1} \sqrt{s}=13 TeV pp collision data collected by the ATLAS experiment. a is considered to be a beyond standard model particle or a standard model charmonium state. The mass of a is less than 4 GeV and it is required to decay to quarks or gluons, while Z boson decays to two leptons. No significant excess above the expected background is observed. The observed 95% confidence-level upper limits are set on the branching ratio of Higgs boson decays to a Z boson and the a resonance, with values starting from 13.9% for a decays to gluons, and from 9.2% for a decays to a pair of quarks for different a masses.
The search also considers the axion-like particle models. 95% confidence-level upper limits are set on the strength of the effective coupling C_{Zh}^{eff} with 2.0 TeV^{-1} for 0.5 GeV axion-like particle a, and 0.9 TeV^{-1} for 1.0 GeV a.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):