Speakers
Description
The Standard Model of particle physics, while remarkably successful in describing most phenomena related to the fundamental interactions and particles, notably lacks a mechanism to account for dark matter, prompting a wealth of beyond the Standard Model (BSM) theories that propose various candidates and interactions. One such theory is the dark Higgs boson model. This model introduces three additional states: the dark matter candidate; a dark Higgs boson responsible for giving mass to the dark matter candidate; and a heavy spin-1 mediator ($Z'$). It is able to reproduce the observed relic density naturally. A search for a di-Higgs resonance will be presented, with each Higgs decaying to two b-jets, paired with significant missing transverse momentum (MET), in 140/fb of $pp$ collision data recorded by the ATLAS experiment at $\sqrt(s)=13$ TeV. This signature provides the first sensitivity for the process where the $Z'$ radiates a dark Higgs, the $Z'$ decays to two dark matter particles, and the dark Higgs into two Higgs bosons, likely for a sufficient dark Higgs mass. A specialised neural network approach is used, decorrelated with the di-Higgs mass (a proxy for the dark Higgs mass), to enhance the sensitivity of our search, enabling the analysis to probe the previously unexplored parameter space of high $Z'$ and dark-Higgs masses.
