Mono-Higgs signature in a singlet fermionic dark matter model
We investigate mono-Higgs production as a probe of singlet fermionic dark matter (SFDM) at the LHC. In this framework, a Standard Model (SM) gauge-singlet Dirac fermion serves as the dark matter candidate, interacting with the visible sector through a real scalar mediator that mixes with the SM Higgs boson. Focusing on the light dark matter regime with masses at or below the GeV scale, we analyze the viable parameter space under constraints from relic density, Higgs decay properties, invisible decay bounds, rare $B$-meson decays, and direct detection experiments. We compute the mono-Higgs production cross sections at $\sqrt{s}=13~\mathrm{TeV}$ and compare the predicted event yields with current ATLAS and CMS results. We find that the dominant contribution arises from di-Higgs production followed by the invisible decay of one Higgs boson, with the rate largely controlled by the scalar trilinear coupling. For representative benchmark points consistent with all current constraints, the predicted signal remains below existing experimental limits. Despite the current non-observation, the mono-Higgs channel provides a complementary probe of Higgs-portal dark matter scenarios, particularly in the low-mass mediator regime. Our results indicate that future high-luminosity LHC data may enable significant exploration of the viable SFDM parameter space.