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Author ORCID Identifier


Open Access Dissertation

Document Type


Degree Name

Doctor of Philosophy (PhD)

Degree Program


Year Degree Awarded


Month Degree Awarded


First Advisor

Benjamin Brau

Subject Categories

Elementary Particles and Fields and String Theory


A search is performed for long-lived neutral particles using 33 fb−1 of 13 TeV proton-proton collision data produced by the LHC and collected by the ATLAS detector during 2016. This search focuses on the topology in which pairs of displaced hadronic jets are produced, with one in the inner detector and the other in the muon spectrometer. Special techniques are used to reconstruct the displaced decays. One event is found passing the full signal selection, which is consistent with the back- ground estimation. Limits are set at a 95% upper confidence level on the BR × σ for a SM Higgs, or scalar boson Φ of mass 200 to 1000 GeV, to decay to long-lived hidden sector particles of masses 8 to 400 GeV. The limits placed on the branching ratio of the Higgs boson and the BR × σ of a 200 GeV Φ to several long-lived neutral scalars extend existing exclusion limits between long-lived particle lifetimes from 5 cm to 1 m.