Simulation of dark scalar particle sensitivity in η rare decay channels at HIAF

Abstract The search for dark portal particles is a prominent topic at the frontier of particle physics. We present a simulation study of an experiment suitable for searching for scalar portal particles at the Huizhou η factory. The high-intensity proton beam from HIAF and a high event-rate spectrometer are suggested to conduct this experiment, both of which are well-suited for the discovery of new physics. Under a conservative estimation, η events could be produced during a one-month operation of the experiment. The hadronic production of η mesons ( ) was simulated at a beam energy of 1.8 GeV using the GiBUU event generator. We searched for light dark scalar particles through rare decay channels, namely and . The detection efficiencies of the channels and the spectrometer resolutions were studied in the simulation. We also present the projected upper limits of the decay branching ratios of the dark scalar particle and the projected sensitivities to the model parameters.