MPG-Logo
The image shows a beaker containing a highly concentrated sugar solution. Inside this vessel is a nylon thread on which a small sugar crystal has formed.

Sucrose crystals on a nylon thread. They formed in a test tube containing a highly concentrated sugar solution (Photo: Beatrice Mauri)

Dark matter: Detection with sugar?

Study investigates sucrose as a possible detector material

The nature of dark matter remains a mystery. Particles of different masses are possible candidates. For some time now, researchers have been searching for very light dark matter particles, for which novel detection methods must be developed. A working group at the Max Planck Institute for Physics has experimented with sugar as a detector material for the first time. Initial tests have been promising—but there are still a few hurdles to overcome.

Text CRESST is an experiment designed for light WIMPs (weakly interacting massive particles), which are dark matter particles. The detection principle is based on a behavior familiar from billiard: when a dark matter particle collides with one of the atomic nuclei in the crystal, it bounces back. The energy of the recoil can be measured as a minimal increase in temperature and as a faint light.

The benefits of sugar

Searching for light dark matter requires special detector materials, as Federica Petricca, scientist at MPP and spokesperson for CRESST, explains: “We are always looking for new appropriate detector materials, better if they consist of light atomic nuclei. This is because a very light dark matter particle cannot disturb much a heavy atomic nucleus, just as a marble cannot move a bowling ball when it collides with it.”

Their considerations led the scientists to ordinary household sugar, sucrose. “At first, the idea seemed far-fetched to us. We found no evidence of previous tests,” reports Federica Petricca. Yet the material is almost perfect: in addition to carbon and oxygen, sugar has a total of 22 hydrogen atoms. And with only one proton, hydrogen is the lightest element that exists.

However, dark matter is unlikely to be discovered with sugar from the supermarket. “Since we need particularly pure and large crystals for our experiments, we have to grow them ourselves in a complex process that takes several weeks,” explains Federica Petricca.

Promising results

The sugar cubes were equipped with temperature and light sensors and exposed to a source of radioactivity. A light signal and a rise in temperature were indeed recorded on the crystal. “The result surprised us, because sucrose forms a rather soft crystal,” explains Federica Petricca. “Materials with a hard crystal lattice are more favorable, since particle collisions result in larger temperature changes.”

Nevertheless, the team is very satisfied with its creative, “sweet” approach: “We have shown for the first time that sugar is fundamentally suitable as materials for detecting dark matter,” says Federica Petricca. “However, only after many more tests and comparisons with other materials will it become clear whether a sucrose detector can be realized.” So, the sugar still has to prove itself.

Top view of two rectangular laboratory containers, each containing an experimental dark matter detector: Left: A large sugar crystal was fitted with a small temperature sensor, which was mounted in a copper holder. Right: The sucrose crystal is additionally equipped with a light sensor that covers the crystal and temperature sensor. There are additional sugar crystals on the bottom of the container that were not used for the test.mit einem experimentellen Dunkle-Materie-Detektor: Links: Ein großes Zuckerkristall wurde mit einem kleinen Temperatursensor versehen, der in eine Kupferhalterung montiert wurde. Rechts: Der Saccharose-Kristall ist hier zusätzlich mit einem Lichtsensor bestückt, der den Kristall samt Temperatursensor verdeckt. Auf dem Boden des Behälters befinden sich weitere Zuckerkristalle, die nicht für den Test verwendet wurden.
Left: A sucrose crystal with a temperature sensor. Right: The sugar crystal is additionally equipped with a light sensor, which covers the crystal and the temperature sensor. There are more sugar crystals at the bottom of the container (Photos: Beatrice Mauri)
Print