This dissertation presents the development, calibration, and application of a newly developed double b-tagger for use in the context of exotic Higgs decays. After the discovery of the Higgs boson at the Large Hadron Collider, an effort to measure its properties in detail has ensued. Current measurements only constrain non- Standard Model or “exotic” Higgs decays to about < 26%. Allowing the Higgs to decay into new particles could remedy some outstanding problems in the Standard Model like dark matter or the matter/anti-matter asymmetry in the universe. Thus, an exciting window of opportunity exists for new physics.
The exotic Higgs decays investigated in this work have the Higgs decay into a new spin-zero particle, a. The a-boson then decays into a pair of b-quarks. For low a masses, the b-quarks from the same parent a tend to be collimated. This results in signatures that previous ATLAS reconstruction techniques could not efficiently find. With a newly developed tagger, the H → 2a → 4b search in the low mass regime was able to be performed
