Light Dark Matter eXperiment: The Search for Visible Decays

The particle nature of dark matter is still unknown, yet there are dark particle candidates spanning a large mass range. One of the simplest possibilities of dark matter's origin is one in which dark matter arose as a thermal relic from the hot early universe. In this case, its mass range is expected to be between 1 MeV to 100 TeV. Below 1GeV is not readily available to direct-detection experiments and is therefore largely unexplored in dark matter experiments. LDMX (Light Dark Matter Experiment) allows us to search for these dark particles. It will use the fact that the thermal freeze-out scenario requires that there be an interaction between dark matter and ordinary matter. If such an interaction exists, an electron beam might produce a dark photon through a fixed target collision. A significant loss of beam energy with no other observable particles could signal the production of one such dark particle. However, the dark photon can also decay back into a visible pair of particles: an event that would go unflagged in the current LDMX design. We investigate how well we could detect these visible events with slight modifications to the LDMX trigger and analysis strategy.