The XENON detector, with its low-background cryostat, is installed in the center of a large water shield to protect the instrument against cosmic ray backgrounds. This setup enables the scientists working on the XENON experiment to greatly reduce their background noise, and more confidently discover the signals from processes they’re attempting to study. XENON is not only searching for heavy, WIMP-like dark matter, but other forms of potential dark matter and even dark energy as well. (Credit: XENON Collaboration)

XENON experiment puts the squeeze on WIMPy dark matter

With a bigger, better, and more sensitive detector than ever before, the XENON collaboration leaves little wiggle room for WIMP dark matter.

When it comes to the question of “what makes up the Universe,” the Standard Model simply doesn’t add up. When we add up all of the normal matter — stuff made up of quarks and charged leptons — we find that it’s only responsible for about 1/6th of the total “mass” that must be out there. Additionally, observations of individual galaxies, of groups and clusters of galaxies, of the cosmic microwave background, and of the large-scale structure of the Universe all paint the same picture: a Universe where 5/6ths of the mass out there isn’t made of any Standard Model particle, but rather is invisible, cold, and non-interacting except through the gravitational force.

We call this massive species of matter that must exist, but whose nature remains unknown, dark matter. This dark matter must be cold (i.e., moving slow compared to the speed of light) at even early times, teaching us that if it ever were in thermal equilibrium with the “primordial particle soup” of the hot Big Bang, it must be quite a massive species of particle. These classes of particles — that interact only very weakly but that have large…