Searching for long-lived dark sector particles with the SpinQuest Experiment at Fermilab

Searching for light, weakly-coupled dark sector particles is of vital importance in worldwide dark matter searches. Long-lived dark mediators may be generated through interactions between proton beam and fixed target at the SpinQuest experiment (E1039) at Fermilab. These hypothetical long-lived particles will travel several meters before decaying into SM particles and can be tracked by the dedicated spectrometer. We developed a new dimuon trigger system to improve the efficiency of displaced signals. A further upgrade will add an electromagnetic calorimeter to the current detector to extend the detection capability to electron, photon, and hadronic final states. With this dedicated effort, we can perform new world-leading searches within the next few years. In the summer of 2024, we received the first 120 GeV proton beam and successfully completed beam commissioning. We will continue to collect the physics data in the next two years to achieve the target luminosity of 10^18 proton on target. In this presentation, I will discuss the current status and plans of our dark sector particle search.