A global collective of researchers has published its first study on its search for dark matter.
Led by the PRISMA+Cluster of Excellence at Johannes Gutenberg University Mainz (JGU) and Helmholtz Institute Mainz (HIM) in Germany, researchers have published their results on their search for dark matter in Nature Physics. The project was made possible by a network of 14 different observers in eight countries worldwide. The observation sites are based in Germany, Serbia, Poland, Israel, South Korea, China, Australia, and the United States.
Dark matter accounts for a lot of the universe (80%) and is the presumed cause of confusing astronomical observations, “such as the rotation speed of stars in galaxies or the spectrum of the cosmic background radiation,” explained scientists in a press release from JGU Mainz. However, scientists have never observed dark matter, except for circumstantial evidence of its gravitational interactions.
Researchers searched for evidence of dark matter using a Global Network of Optical Magnetometers for Exotic physics searches (also known as GNOME). Optical magnetometers are instruments that measure the strength and direction of magnetic fields.
Nine of the sites participated in data collection for this paper. Researchers turned to bosons to detect dark matter, which are subatomic particles with quantum spins equal to an integer (0, 1, 2 …). Researchers set up atoms and excited them with a laser to make them “spin” together. Any interaction with dark matter would then, in theory, change the direction of some of those spins, which the magnetometer would be able to measure.
Hector Masia-Roig, a doctoral student at PRISMA+ and HIM, explains: "When [atoms] 'hear' the right frequency of laser light, they all spin together. Dark matter particles can throw the dancing atoms out of balance, and we can measure this perturbation very precisely."
A single instance of an atomic spin abnormality isn’t enough to prove an interaction with dark matter, so the network of stations each provide a data point in the bigger picture. “If we compare the measurement results from all the stations, we can decide whether it was just one brave dancer dancing out of line or actually a global dark matter disturbance,” Masia-Roig said.
After a month of observation, no statistically significant signals appeared in the mass range of one femtoelectronvolt (feV) to 100,000 feV. However, this is not a failure because it allows researchers to narrow down the range at which dark matter signals could be observed.
In the future, the GNOME project will continue to improve their magnetometers to be more stable, thus allowing them to operate longer than an hour. This should allow them to search more continuously and increase the chances of dark matter observation. They also intend to replace the alkali atoms used in the magnetometers with noble gases, which will give the instruments greater sensitivity.
These improvements will continue under the title of “Advanced GNOME,” which researchers hope will yield more accurate results in the search for dark matter.
Sources: Johannes Guttenberg University Mainz, Nature Physics
