CERN Accelerating science

ATLAS Slides
Report number	ATL-PHYS-SLIDE-2025-403
Title	Hunting the dark-Higgs: A search for a dark-Higgs boson in the 4b+MET final state at $\sqrt{s}=13$ TeV with the ATLAS detector
Author(s)	Dingley, Thomas Benjamin (University of Oxford (GB))
Corporate author(s)	The ATLAS collaboration
Collaboration	ATLAS Collaboration
Submitted to	The 32nd International Symposium on Lepton Photon Interactions at High Energies (Lepton Photon 2025), Madison, Wisconsin, Us, 25 - 29 Aug 2025
Submitted by	thomas.dingley@cern.ch on 28 Aug 2025
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN LHC ; ATLAS
Free keywords	SUSY ; EXOTICS
Abstract	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.