A search for invisible decays of the Higgs boson as well as searches for dark matter candidates, produced together with a leptonically decaying Z boson, are presented. The analysis is performed using proton−proton collisions at a centre-of-mass energy of 13 TeV, delivered by the LHC, corresponding to an integrated luminosity of 139 fb−1 and recorded by the ATLAS experiment. Assuming Standard Model cross-sections for ZH production, the observed (expected) upper limit on the branching ratio of the Higgs boson to invisible particles is found to be 19% (19%) at the 95% confidence level. Exclusion limits are also set for simplified dark matter models and two-Higgs-doublet models with an additional pseudoscalar mediator.

Aad, G., Abbott, B., Abbott, D.C., Abed Abud, A., Abeling, K., Abhayasinghe, D.K., et al. (2022). Search for associated production of a Z boson with an invisibly decaying Higgs boson or dark matter candidates at s=13 TeV with the ATLAS detector. PHYSICS LETTERS. SECTION B, 829, 137066 [10.1016/j.physletb.2022.137066].

Search for associated production of a Z boson with an invisibly decaying Higgs boson or dark matter candidates at s=13 TeV with the ATLAS detector

I. Bashta;M. T. Camerlingo;V. D'Amico;B. Di Micco;R. Di Nardo;D. Orestano;F. Petrucci;G. Salamanna;