Search for the production of dark Higgs in the framework of Mono-Z$^{\prime}$ portal at the FCC-ee simulated electron-positron collisions at $\sqrt{s} = 240$ GeV

We conducted a Monte Carlo search for dark Higgs particles ($h_{D}$), which is based on a model derived from the Mono-Z$^{\prime}$ portal. This model suggests the existence of $h_{D}$ and a new neutral gauge boson, denoted as Z$^{\prime}$. Our study focused on the event topology featuring two oppositely charged muons and missing transverse energy, generated from simulations of $e^+ e^-$ collisions at the Future Circular Collider (FCC-ee). This collider is set to operate with 240 GeV a center-of-mass energy ($\sqrt{s}$), and will achieve an integrated luminosity of 10.8 ab$^{-1}$. In our analysis, we estimated upper limits on the mass of the dark Higgs at a 95\% confidence level, assuming that no $h_{D}$ particles were detected.