Search for Hidden Valley dark showers with displaced muons with the CMS experiment
File(s)
Author(s)
Law, Kai Hong
Type
Thesis
Abstract
A search for signatures of a dark analog to quantum chromodynamics is performed. The analysis targets long-lived dark mesons that decay into Standard Model particles with a high branching fraction to muons. It is the first search at the Large Hadron Collider (LHC) that targets the decay of Hidden Valley dark showers into muons. A unique dataset with 10^10 B meson events is used. It was collected by the CMS experiment at the CERN LHC in 2018 using displaced muon triggers, which have high efficiency for the signal models. Resonant dimuon signatures are searched for, with both pointing and non-pointing topologies. No significant excess is observed beyond the Standard Model expectation. Upper limits on the branching ratio of the Higgs boson decays to dark partons are determined to be as low as about 10^-4, at 95% confidence level, surpassing and extending existing limits for the mean proper lifetime of less than approximately 0.1 m and for a mass as low as 2 GeV. First limits are set for extended dark shower models, probing the low-mass region down to 0.33 GeV.
Version
Open Access
Date Issued
2025-05-12
Date Awarded
01/08/2025
License URL
Advisor
Tapper, Alexander
Publisher Department
Department of Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)