A Search for Resonant Cascades to Neutral Standard Model Bosons and pTmiss and Selected Stories of the CMS Hadron Calorimeter Phase 1 Upgrade

Direct decays of proposed heavy force mediator particles to standard model (SM) leptons have been excluded to high masses, but more complex scenarios remain unexplored. This thesis presents a search for a leptophobic Z’ decaying via anomalons in proton-proton collisions at a center of mass energy of 13 TeV with the Compact Muon Solenoid (CMS) Experiment. A leptophobic Z’ can decay via a pair of anomalons, new beyond the standard model (BSM) fermions introduced to cancel the gauge anomalies arising from the leptophobic condition. These heavy intermediate particles decay in turn to neutral SM bosons and lighter, stable anomalons. The stable anomalons can serve as a dark matter candidate. This analysis targets the ZH → μμ̄bb— p ⃗ T miss final state in a total integrated luminosity of 137.6 fb −1 corresponding to the 2016-2018 data set. To search for the resonant Z’ production, this analysis employs Recursive Jigsaw Reconstruction (RJR), an iterative framework to reconstruct mass estimators in systems with invisible particles in the final state. This thesis presents the expected sensitivity of this novel model and observable in a CMS search. Additionally, the assembly, installation, and commissioning of CMS Hadron Calorimeter Phase 1 upgrade is discussed.