by A new experiment designed to search the cosmos for its “stuff,” dark and mysterious matter, has achieved its first results.
Although the Broadband Reflector Axion Detection Experiment (BREAD) developed by the University of Chicago and the US Department of Energy’s Fermilab has not yet detected dark matter particles, the new results provide a tighter constraint on what kind of characteristics scientists may have expecting them. have such particles. The BREAD experiment itself has also provided an exciting new recipe that could be used to search for dark matter – something that’s relatively cheap and doesn’t take up much space.
BREAD takes a “broadband” approach to searching for hypothetical dark matter particles called “axions” and related “dark photons” over a larger range of possibilities than other experiments, albeit with somewhat less precision.
“If you think about it like a radio, the search for dark matter is like tuning a dial to search for one particular radio station, except there are a million frequencies to check through,” University of Chicago scientist and BREAD project co-leader David Miller said in a statement. “Our method is like scanning 100,000 radio stations, rather than a few thoroughly.”
Related: What is dark matter?
A small experiment to tackle a big problem
Dark matter is a huge problem for scientists because, despite it making up about 85% of the matter in the universe and its influence preventing galaxies from flying apart as they spin, we have little idea of what it is made of.
That’s partly because dark matter is effectively invisible; it doesn’t seem to interact with light, it doesn’t emit or reflect normal photons. That lack of electromagnetic interaction suggests that dark matter is not made up of the protons, neutrons and electrons that make up “normal matter” objects like stars, planets, moons, our bodies and the cat next door.
Although our telescopes cannot detect dark matter directly, the stuff affects stars, galaxies and even light through its interactions with gravity. So astronomers can say something is there – they just don’t know what it is. Knowing what to look for and exactly where to look is a different matter.
“We are very confident that there is something there, but there are many, many forms it could take,” said Miller.
This confusion has led scientists to search for various particles with strange properties that could comprise dark matter. One such candidate is the axion, a hypothetical particle with an extremely small mass. If axes exist, they can interact with so-called dark photons, just as normal matter interacts with “normal” photons. This interaction may occasionally trigger the creation of a visible photon under certain circumstances.
BREAD is a coaxial dish antenna in the shape of a curved metal tube that can fit on a table top. The experiment is designed to capture photons and funnel them to a sensor at one end to search for a subset of possible axes.
The full-scale BREAD experiment will see the equipment sit inside a strong magnetic field, which the team says will increase the chance of converting axons into photons. As a proof of principle, the team performed the BREAD experiment minus the magnets needed to generate this field.
The proto-BREAD experiment ran at the University of Chicago for a month and provided some interesting data, which really fueled the team’s enthusiasm for the whole experiment. The results of the tests showed that BREAD was extremely sensitive to the range of frequencies the team had designed to explore.
“This is just the first step in a series of exciting experiments we are planning,” said BREAD co-leader and Fermilab researcher Andrew Sonnenschein. “We have many ideas for improving the sensitivity of our action search.”
The test also showed that particle physics can be done on a tabletop and with massive particle accelerators such as the Large Hadron Collider (LHC), which runs 17 miles (27 kilometers) deep under the border between France and Switzerland.
“This result is a milestone for our concept, demonstrating for the first time the power of our approach,” said Stefan Knirck, the Fermilab postdoctoral scholar who led the development and construction of BREAD. “It’s amazing to do this kind of creative science at a tabletop scale, where a small team can do everything from experiment construction to data analysis and still have a big impact on modern particle physics.”
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The next phase of the BREAD experiment will transport the apparatus to the magnetization facility at Argonne National Laboratory. In addition, facilities such as the SLAC National Accelerator Laboratory, MIT, Caltech, and NASA’s Jet Propulsion Laboratory are working on research and development with the University of Chicago and Fermilab for future recipes for the BREAD experiment.
“There are still so many open questions in science and huge room for new, creative ideas to tackle those questions,” Miller said. “I think this is a real example of those kinds of creative ideas—in this case, impactful collaborative partnerships between smaller-scale science at universities and larger-scale science at national labs.”
The team’s research is detailed in a paper published late last month in the journal Physical Review Letters.
