September 4, 2025
The DAMIC-M darkish matter detector sits beneath the Alps beneath 5,000 toes of rock to guard it from cosmic rays and different sources of noise. The Milky Way and nearly all different galaxies are held collectively by darkish matter, although scientists have but to straight observe the mysterious substance.iStock
When scientists observe the cosmos, they see stars whizzing round their galaxies sooner than the legal guidelines of physics ought to enable and clusters of galaxies attracting one another too strongly. They theorize that one thing should be producing extra gravity than all of the seen matter in existence may clarify — however regardless of the substance is, it’s invisible. Dark matter is, successfully, a placeholder: A well-documented gap in our understanding of the universe.
Researchers have floated numerous theories to elucidate what darkish matter is likely to be, however so far, no experiment has turned up compelling proof to help any of them. An worldwide group of physicists is now engaged on a brand new form of darkish matter detector with the aim of capturing the primary direct statement of the puzzling materials. Results from the detector’s prototype have already dominated out one of many main theories of how darkish matter originated.
The new research was published August 13 in Physical Review Letters.
“DAMIC-M may be our best shot to answer the dark matter question in the coming years,” mentioned Alvaro Chavarria, a University of Washington affiliate professor of physics and detector lead for the DAMIC-M (DArk Matter In CCDs at Modane) worldwide collaboration, which carried out this research.
A DAMIC-M detector module with silicon CCDs. The module is enclosed in a high-purity copper body for set up within the detector prototype.DAMIC-M Collaboration
Most physicists assume that darkish matter is fabricated from particles, identical to all different matter within the universe. For causes unknown, this class of particles doesn’t work together a lot with standard matter or with photons of sunshine. But it may work together simply sufficient to be noticed by a extremely delicate instrument because the darkish matter particles zip by way of the Earth.
“We know how much dark matter there is in the universe, but we don’t know whether it’s made of many light particles, or fewer, heavier ones,” Chavarria mentioned. “The game is to rule out all possible hypotheses until we find something.”
For years, the main candidate for darkish matter was a heavy theoretical particle recognized cheekily because the WIMP, or Weakly Interacting Massive Particle. But experiments haven’t revealed a single WIMP, so many researchers have pivoted their search to lighter candidates referred to as “hidden-sector” particles. Lighter particles could be that a lot tougher to measure, so to satisfy the problem, Chavarria and the DAMIC-M group developed a brand new class of detector.
The new gadget works a bit like a digital digicam, which makes use of a silicon sensor referred to as a CCD fabricated from tens of millions of pixels. The sensor detects photons and turns them into a picture. The darkish matter detector is made of comparable — although way more delicate — CCDs that may choose up tiny and uncommon particle interactions.
Chavarria and his group assembled and examined the CCD modules of their UW clear room lab. They then despatched the gadget straight to the Laboratoire Souterrain de Modane, a facility situated beneath 5,000 toes of rock within the French Alps. There, it was encased in result in shield it from radioactive parts within the surrounding rock, and introduced on-line. All of this was finished to conduct the experiment with pristine equipment.
“We’re looking for very rare signals in the detector — maybe on the order of one signal in a year,” Chavarria mentioned. “You need to remove all types of interference from other forms of radiation.”
Researchers set up the copper field containing the detector modules. Surrounding the field is shielding fabricated from lead from historical Rome — the group selected lead so outdated that any radioactive contaminants inside it could have already decayed.DAMIC-M Collaboration
As superior because the instrument is, it’s only a prototype. The DAMIC-M group is constructing a a lot bigger, extra delicate detector proper now; they plan to carry it on-line early subsequent yr. Still, the prototype has confirmed helpful. For two and half months, it captured a number of thousand “photographs,” which the group scoured for proof of darkish matter collisions. It discovered none.
But within the sport of darkish matter detection, the absence of a discovering is a discovering in itself.
Historically, scientists have weighed two doable situations for the way hidden-sector particles may have shaped early within the lifetime of the universe. Each state of affairs makes a distinct prediction for the way the particles would possibly flip up at the moment. If the hidden-sector concept is appropriate, a type of two situations ought to be correct. The “null” end result by the DAMIC-M prototype nearly fully guidelines out one of many situations — and the full-scale detector is delicate sufficient to complete the job. Either the brand new detector will uncover darkish matter, Chavarria mentioned, or it will likely be time to check new theories.
“If DAMIC-M doesn’t see anything, I don’t think you’ll hear about hidden-sector models of dark matter anymore.”
The DAMIC group closes up the prototype detector after putting in the CCDs.DAMIC-M Collaboration
Other prospects exist. Perhaps hidden-sector particles exist, however solely account for a small quantity of all of the darkish matter within the universe. Perhaps tiny particles referred to as axions are within the combine too — they’re the goal of another detector housed at the UW. In different phrases, possibly darkish matter is one other particle — or multiple.
But with DAMIC-M, researchers can slim down the variety of present theories to these value investigating, all whereas constructing the expertise obligatory to take action.
“We’ve been working on this since I arrived at the UW in 2018,” Chavarria mentioned. “The module development alone took almost five years of work here on campus. And now, thanks to the amazing result we got from the prototype, we’re pretty confident the full-scale detector is going to work. I’m very excited. This was the dream.”
Co-authors embody Heng Lin, a former UW postdoctoral researcher who’s now a postdoctoral fellow at Johns Hopkins University; Kellie McGuire, who accomplished this analysis as a UW graduate scholar; Michelangelo Traina, a former UW postdoctoral researcher who’s now a postdoctoral fellow on the Instituto de Física de Cantabria in Spain and Kush Aggarwal, a UW graduate scholar. A full checklist of co-authors is included with the paper.
This analysis was funded by the European Research Council; National Science Foundation; The Kavli Foundation; The Ministry of Science and Innovation, Spain; Swiss National Science Foundation; and Centre National de la Recherche Scientifique (CNRS).
For extra data, contact Chavarria at chavarri@uw.edu.
This story was tailored from a press release by the University of Chicago.
Tag(s): Alvaro Chavarria • College of Arts & Sciences • darkish matter • Department of Physics