Modern cosmology is often associated with massive observatories, advanced instruments, and large international collaborations backed by significant funding. However, meaningful progress does not always require such scale. Even in the complex search for dark matter, smaller teams with creative approaches and institutional support can still make important contributions.
A recent study published in the Journal of Cosmology and Astroparticle Physics (JCAP) highlights this idea. A group of undergraduate students from the University of Hamburg designed and built a cavity detector to search for axions, which are among the leading candidates for dark matter. Despite working with limited resources, they were able to establish new experimental limits on axion properties, demonstrating that smaller experiments can still advance one of physics' biggest unresolved problems.
The project was funded through a student research grant from the University of Hamburg, provided by the Hub for Crossdisciplinary Learning. This program supports independent research projects led by students.
"We were kind of embedded in the research group of the MADMAX dark matter experiment," explains 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 adds, "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."
"The benefit of working with dark matter, or axions, is that we expect it to be present everywhere in our galaxy," says Agit Akgümüs, the study's first author, who is pursuing an M.Sc. in Mathematical Physics at the University of Hamburg. "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 assembled a compact experimental setup centered on a resonant cavity made from highly conductive materials. They also integrated the required electronics, cabling, structural supports, and measurement tools.
"The detector we built is essentially the simplest version of a cavity detector for dark matter," says Salama.
The students did not begin entirely from scratch. They made use of existing facilities, equipment, and guidance provided by the university and collaborating research groups. After construction, the system was carefully tested, calibrated, and operated to collect data.
"We reduced very complex experiments to their essential components," says Salama. "The result is a less sensitive setup, limited to a small search window, but still capable of producing new scientific data."
No Detection, but Important New Constraints
"The search for axions involves exploring a wide range of possible parameters," adds Akgümüs. "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."
After completing their data collection, the team did not detect any signal that could be attributed to axions. However, this outcome still carries scientific value. It allows researchers to rule out the existence of axions with certain characteristics within the tested mass range, especially those that would interact more strongly with photons. By excluding these possibilities, the study helps refine the search and guide future experiments.
"I think the point of our experiment is that things can be done on a smaller scale," says Salama. Akgümüs adds: "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."
During peer review, one referee made an especially notable observation, Salama recalls. The referee suggested that once the axion is discovered and its properties -- especially its mass -- are known, experiments like this could become much more accessible and might even be used in teaching laboratories.
"We were told that setups like ours could one day become standard student lab experiments," says Salama. "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."
