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Physicists force dark matter

This image of Centaurus A, one of Earth's closest active galaxies, combines data from observations in multiple frequency ranges. Credit: ESO / WFI (optical), MPIfR / ESO / APEX / A. Weiss et al. (Submillimeter), NASA / CXC / CfA / R. Kraft et al. (Roentgen)

Researchers from Russia, Finland and the US have limited the theoretical model of dark matter particles by analyzing data from astronomical observations of active galactic nuclei. The new findings provide an additional incentive for research groups around the world to try to crack the mystery of dark matter: no one is quite sure what it is made of. The article was published in the Journal of Cosmology and Astroparticle Physics .

The question of which particles dark matter consists of is of decisive importance for modern particle physics. Despite the expectation that dark matter particles will be detected in the Large Hadron Collider, this is not the case. A series of then prevailing hypotheses about the nature of dark matter had to be rejected. Various observations suggest that dark matter exists, but apparently this is different from the particles in the Standard Model. Physicists must therefore consider other, more complex options. The standard model needs to be extended. Among the candidates for inclusion are hypothetical particles having masses in the range of 1

0 & supmin; ² & sup0; to 10 & supmin; ¹ & sup0; times the mass of the electron. That is, the heaviest speculated particle has a mass 40 orders of magnitude larger than the lightest.

A theoretical model treats dark matter as mass consisting of ultralight particles. This provides an explanation for numerous astronomical observations. However, such particles would be so light that they would interact very weakly with other materials and light, making them extremely difficult to study. It is almost impossible to detect such a particle in a laboratory, which is why the researchers turn to astronomical observations.

"We are talking about dark matter particles that are 28 orders of magnitude lighter than the electron, which is crucial to the model we chose to do: The interaction of gravity reveals the presence of dark matter: Explaining the mass of dark matter in terms of ultra-light particles would mean that there are a tremendous number of them. As light as this, the question arises: how do we protect them from gaining effective mass due to quantum corrections? One possible answer is that these particles interact only weakly with photons, ie with electromagnetic radiation. To study them: by observing electromagnetic radiation in space, "said Sergey Troitsky, co-author of the paper and chief researcher at the Institute for Nuclear Research of the Russian Federation Academy of Science.

If the number of particles is very high, you can treat them instead of individual particles as a field of specific density that permeates the universe. This field oscillates coherently over domains as large as about 100 parsecs or about 325 light years. What determines the oscillation period is the mass of the particles. If the model considered by the authors is correct, this period should be about one year. When polarized radiation passes through such a field, the plane of radiation polarization oscillates at the same period. If such periodic changes actually occur, astronomical observations can reveal them. And the length of the period – a terrestrial year – is very favorable, since many astronomical objects are observed over several years, which is enough to manifest the polarization changes.

The newspaper's authors decided to use the data from Earth-based radio telescopes because they return many times to the same astronomical objects during an observation cycle. Such telescopes can observe distant active galactic nuclei – regions of superheated plasma near the centers of galaxies. These areas emit highly polarized radiation. If you observe them, you can follow the change in the polarization angle over several years.

"At first, the signals of the individual astronomical objects seemed to have sinusoidal vibrations, but the problem was that the sinus period must be determined by time The mass of dark matter, that is, it must be the same for every object There were 30 objects in our sample, and it may be that some of them oscillated due to their own internal physics, but still the periods were never the same. "Troitsky continues. "This means that the interaction of our ultralight particles with radiation may be limited, we do not say that such particles do not exist, but we have shown that they do not interact with photons, which limits the available models that describe the composition." Dark Matter. "

" Imagine how exciting that was! You spend years studying quasars when theoretical physicists emerge one day, and the results of our high-precision, high-resolution polarization measurements are suddenly helpful in understanding the nature of dark matter, "adds Yuri Kovalev, co-author of the Study and Laboratory Director at the Moscow Institute of Physics and Technology and the Lebedev Physical Institute of the Russian Academy of Sciences.

In the future, the team plans to search for manifestations of hypothetical heavier particles of dark matter proposed by other theoretical models According to Troitsky, the restrictions on alternative models are more stringent.

"At the moment, the whole world is looking for particles of dark matter. This is one of the great mysteries of particle physics. To date, no model is considered to be favored, better developed, or more plausibly adopted in terms of available experimental data. We have to test them all. Unfortunately, dark matter is "dark" in the sense that it barely interacts with anything, especially light. In some scenarios, this could have a negligible effect on passing light waves. Other scenarios, however, do not predict any interactions between our world and dark matter, other than gravity-mediated ones. This would make the particles very hard to find, "concludes Troitsky

Explore further:
CERN laboratory on the hunt for dark matter

Further information:
M.M. Ivanov et al. Limitation of photon coupling of ultralight dark matter particles in Axion form by polarization variations of parsec jets in active galaxies. published on February 28, 2019 in Journal of Cosmology and Astroparticle Physics . DOI: 10.1088 / 1475-7516 / 2019/02/059

Provided by:
Moscow Institute of Physics and Technology

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