Prof. Eric Dahl and his group build particle detectors for the direct detection of dark matter. There is ample evidence that dark matter exists – its signature is seen on scales from single galaxies to the entire visible universe and across time from the cosmic microwave background (a snapshot of the universe at 400,000 years old) to the present day. These gravitational effects, however, tell us little about the nature of dark matter itself. We know only that it is 5x more abundant than the protons, neutrons, and electrons that make up normal matter, and that it cannot be composed of any particle we’ve identified in the lab so far.
Direct detection experiments look for interactions between the dark matter that surrounds us and the normal matter in specially designed detectors here on earth. Professor Dahl’s group works specifically on searches for WIMPs (Weakly Interacting Massive Particles), a leading dark matter candidate that would interact with normal matter by scattering elastically off atomic nuclei, resulting in a ~10-keV nuclear recoil. Unambiguously identifying this rare signal amid the copious backgrounds produced by natural radioactivity is the crux of the WIMP detection problem. The Dahl group specializes in developing background discrimination techniques in large liquid-based detection technologies capable of the ton-year exposures needed to further explore the WIMP parameter space.