Search for Dark Matter produced in association with a dark Higgs boson decaying to two b-quarks using full Run-2 datasets recorded with the ATLAS detector

A hypothetical dark Higgs boson was proposed in a dark matter (DM) model to explain the origin of mass in the dark sector as well as to open up a new annihilation channel relaxing the DM relic density constraint from cosmological observation. The search focusing on Majorana DM produced with a low mass dark Higgs boson decaying to two b quarks is performed using the 139 fb^-1 of proton-proton collision data collected with ATLAS detector at √s =13 TeV.

The event selection and categorization are optimized based on the varying dark Higgs mass. Full systematics are considered in this analysis, and advanced jet clustering and boosted tagging techniques are applied to reach better sensitivity. Besides the benchmark interpretation on low mass dark Higgs, two additional interpretations will be presented by considering the constraint from freeze-out relic density and new parameter space.