Researchers from seven countries are participating in the experiment to determine the electric dipole moment of the neutron. The photo shows part of the team in front of the research facility at PSI where the studies were conducted. The data obtained here were also used by the researchers in the search for dark matter. (Photo: Paul Scherrer Institute/Markus Fischer)
Measurements at the Paul Scherrer Institute PSI further constrain theories about the nature of dark matter Experts are largely in agreement that a major portion of the mass in the universe consists of so-called dark matter. Its nature, however, remains completely obscure. One kind of hypothetical elementary particle that might make up the dark matter is the so-called axion. If axions exist, it might be possible to detect them at a research facility of the Paul Scherrer Institute PSI - the Ultra Cold Neutron Source UCN. An international team has now analysed measurement results collected at PSI, together with data obtained at the neutron source ILL in Grenoble, and come up with a major negative result: No interaction with axions was observed. These measurements improve on the accuracy of previous measurements, which come from astrophysical observations, by a factor of 1,000 and provide evidence that axions - at least the kind that would have been observable in the experiment - do not exist. This does not rule out the existence of axions, but the scope of characteristics that these particles could have is now distinctly limited.
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