Scientists involved in the search for particles of mysterious dark matter , which accounts for more than 80 percent of the total amount of matter in the universe, managed to exclude one of the candidates , narrowing, therefore, the field of future searches. Researchers at the University of Sussex have found a refutation of the possibility of the existence of certain types of axions , particles that previously were leading candidates for the title of particles of dark matter. This event throws physicists practically to the initial point of their search, but nevertheless, it substantially narrows the area of future searches for particles of dark matter.
As we have already said, dark matter is a very mysterious substance. It does not absorb, does not reflect light, and does not interact with any other kind of electromagnetic radiation, which prevents its particles from being detected by conventional scientific methods. The only manifestation of dark matter is its gravity, which affects the motion of stars, galaxies and clusters of galaxies. The mysterious influence of an unknown substance on the movement of astronomical objects was discovered by astronomers in the 1930s and since that time, physicists have been searching for this invisible substance, which was called dark matter.
In recent years, the list of candidates for the title of particles of dark matter has significantly decreased. First, several experiments conducted by scientistsallowed to exclude from the list of WIMP-particles (Weakly Interacting Massive Particles). And then, the data collected with the Large Underground Xenon (LUX) sensorand the HADES detector indicated that dark matter can not consist of so-called “dark photons” .
Against this background, the axions remained and remain one of the promising candidates. Scientists are now trying to find out whether these hypothetical particles actually exist, what their mass and other parameters are. In this direction, scientists from the Neutron Electric Dipole Moment (nEDM) experiment also worked, whose goal was to narrow the range of the possible mass of axions and which did not give a single positive result.
In the nEDM experiment, neutrons are trapped in a special container, which is then electrified to a high potential. The purpose of this action is to determine whether the high potential of the electric field affects the neutron rotation speed and the frequency of their oscillations. Changes in this frequency with time should indirectly indicate the presence of axions, but, unfortunately or fortunately, no deviations in speed and frequency were recorded. This, in turn, indicates that the axions do not exist in the range of masses and energies that fall within the sensitivity range of the nEDM experiment equipment.
The experiment nEDM was originally conceived to search for an answer to one of the fundamental cosmological riddles. At the time of the birth of the universe, it produced the same amount of ordinary matter and antimatter. In the present Universe there is only ordinary matter, antimatter is present in it only in insignificant quantities. And the experiment nEDM was supposed to give scientists tips on the reasons for the asymmetry of the amount of matter and antimatter. A little later, scientists found that the data of the nEDM experiment could still contain clues regarding the existence of axions.
Despite the lack of a positive result, scientists still admit the possibility of the existence of axions. Only their energy and mass, most likely, are below or above the sensitivity range of the nEDM experiment.
“The results we have obtained do not completely exclude the possibility of the existence of axions, but the area in which it is necessary to continue their search is now significantly narrowed,” says Philip Harris, head of the nEDM group at the University of Sussex. “These results discard physicists practically the initial point of search, nevertheless, further advancement of these searches will go faster and more efficiently than before. “