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Author ORCID Identifier

0000-0002-4690-0528

AccessType

Open Access Dissertation

Document Type

dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Physics

Year Degree Awarded

2021

Month Degree Awarded

September

First Advisor

Ben Brau

Second Advisor

Carlo Dallapiccola

Third Advisor

Jordy de Vries

Fourth Advisor

Alexandra Pope

Subject Categories

Elementary Particles and Fields and String Theory

Abstract

A novel search for exotic decays of the Higgs boson to pairs of long-lived neutral particles, each decaying to a bottom quark pair, is performed using 139 fb-1 of sqrt{s} = 13 TeV proton-proton collision data collected with the ATLAS detector at the LHC. Events consistent with the production of a Higgs boson in association with a leptonically-decaying Z boson are analyzed. Long-lived particle (LLP) decays are reconstructed from inner detector tracks as displaced vertices with high mass and track multiplicity relative to Standard Model processes. The analysis selection requires the presence of at least two displaced vertices, effectively suppressing Standard Model backgrounds. The residual background contribution is estimated using a data driven technique. No excess over Standard Model predictions is observed, therefore upper limits are set on the branching ratio of the Higgs boson to LLPs. Branching ratios of 10% are excluded for LLP mean proper lifetimes as small as 4 mm and as large as 110 mm. For LLP masses below 40 GeV, these results represent the most stringent constraint in this lifetime regime.

DOI

https://doi.org/10.7275/24060127

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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