Big dark matter experiments usually come with big budgets. At the University of Hamburg, a group of undergraduate students took a smaller route and still managed to narrow the search.
The students designed and built a cavity detector to look for axions, hypothetical particles considered among the leading candidates for dark matter, according to a study published in the Journal of Cosmology and Astroparticle Physics.
The project was funded through a student research grant from the University of Hamburg’s Hub for Crossdisciplinary Learning, which supports independent research projects led by students.
“We were kind of embedded in the research group of the MADMAX dark matter experiment,” said Nabil Salama, one of the study’s authors and a current M.Sc. student in physics at the University of Hamburg. “MADMAX carries out a similar experiment on a much larger and more complex scale, and we benefited from their expertise and support.”
“We are very grateful for this help,” he said, “and also to the University of Hamburg and the Quantum Universe Cluster of Excellence, which provided funding, access to key equipment such as the magnet, and invaluable support from researchers.”
Agit Akgümüs, the study’s first author and an M.Sc. student in mathematical physics at the University of Hamburg, said axions are practical to search for because researchers expect dark matter to be spread throughout the galaxy.
“The benefit of working with dark matter, or axions, is that we expect it to be present everywhere in our galaxy,” Akgümüs said. “So essentially, no matter where you perform the experiment, you have some dark matter on your hand you can do experiments with.”
Using their funding, the team built a compact setup around a resonant cavity made from highly conductive materials. They added electronics, cabling, structural supports and measurement tools, and used existing facilities, equipment and guidance from the university and collaborating research groups.
“The detector we built is essentially the simplest version of a cavity detector for dark matter,” Salama said.
After building the system, the students tested it, calibrated it and collected data.
“We reduced very complex experiments to their essential components,” Salama said. “The result is a less sensitive setup, limited to a small search window, but still capable of producing new scientific data.”
The team did not detect a signal that could be linked to axions. But the result still let researchers rule out axions with certain characteristics in the mass range they tested, especially those that would interact more strongly with photons.
“The search for axions involves exploring a wide range of possible parameters,” Akgümüs said. “Our experiment covers only a small region, with limited sensitivity, but it still helps narrow down the possibilities. To actually find the particle, we need either much larger experiments or many different ones, each probing a specific region.”
Salama said the project showed smaller-scale dark matter experiments can still contribute.
“I think the point of our experiment is that things can be done on a smaller scale,” he said.
Akgümüs said the team showed these kinds of setups can be reduced significantly while still producing scientific data.
“Our results are naturally more limited than those of larger experiments. Performance scales with resources and complexity. However, we have shown that it is possible to reduce these setups to a much smaller scale, even to projects developed almost independently by students, while still producing real scientific data,” he said.
Salama said one referee during peer review suggested experiments like theirs could eventually become teaching tools once axions are found and their properties are known.
“We were told that setups like ours could one day become standard student lab experiments,” Salama said. “In a way, we may have anticipated that future, showing that it is already possible to build and operate such an experiment on a small scale.”
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