A Surprising Result in the Search for Dark Matter in an Extended Energy Window of LZ

by Matthew Szydagis (University at Albany)

Monday 19 Oct 2026, 12:45 → 13:45 America/New_York

D-122 (P. Grannis Seminar Room)

For many decades, the tantalizing possibility of vast amounts of unseen matter in the universe that interacts rarely with baryons and leptons has been an enduring mystery in particle physics, astronomy, and cosmology, which together provide evidence this so-called dark matter is 25% of the total mass-energy content (85% of just the matter) of the cosmos. The Weakly Interacting Massive Particle or WIMP is a popular dark matter candidate, well motivated by theoretical physics through supersymmetry and other theories and within cosmology through the concept of a thermal relic. Experiments like LUX-ZEPLIN (LZ) are attempts to directly detect a WIMP. LZ utilizes a ~5.5 tonne fiducial volume of liquid Xenon, an element with many advantages in the search for WIMPs. Recently, the LZ collaboration reported on the results from an exposure of 220 live-days with the LZ detector in a nuclear recoil energy window extending up to 270 keV, instead of a traditional value smaller by an order of magnitude. The larger window is motivated by lack of discovery at lower energies, but more importantly by effective field theory (EFT) and inelastic models where high-energy recoils account for a larger fraction of the predicted recoil spectrum compared to the standard WIMP paradigm. We observed one event with characteristics consistent with a nuclear recoil of 248 ± 23(stat.) ± 23(sys.) keV, in a region of parameter space where no known background was likely to produce even a single count. This result is in tension with the background-only hypothesis at a global significance of 2.6σ.

2026stonyBrookSeminarSzydagis.pdf