11:00 am–12:00 pm ERC 401
Christian Herwig (Fermilab) "The Light Dark Matter eXperiment, LDMX"
The viable dark matter (DM) candidate mass range spans 90 orders of magnitude. The natural scenario where DM originates from thermal contact with familiar matter in the early Universe dramatically restricts this window to ~MeV to ~100 TeV. Considerable experimental efforts have sought Weakly Interacting Massive Particles in the upper end of this range (few GeV to several TeV), while the region ~MeV to ~GeV is largely unexplored. This region must be a priority as several traits converge here: In this lower range, tantalising hints for physics beyond the Standard Model appear, most stable particles of ordinary matter have masses, and the thermal origin for DM works in a simple, predictive way. Thermal-origin DM implies a light DM-ordinary matter interaction— and therefore a production mechanism in accelerator-based experiments. The most sensitive way to probe sub-GeV DM, assuming the interaction is not electron-phobic, is to search for this production using a primary electron beam to manufacture DM in fixed-target collisions. The Light Dark Matter experiment (LDMX) is a planned electron-beam fixed-target missing-momentum experiment with unique sensitivity to sub-GeV DM, as well as a broad range of additional signatures. I will provide an overview of the theoretical motivation, main experimental challenges and their solutions, and projected sensitivities relative to the landscape of other experiments.
