A new model for dark matter

A new model for dark matter

A new model for dark matter

This NASA Hubble Space Telescope image shows the distribution of dark matter at the center of the giant galaxy cluster Abell 1689, which contains about 1,000 galaxies and trillions of stars. Dark matter is an invisible form of matter that accounts for most of the mass in the universe. Hubble cannot see dark matter directly. The astronomers inferred its location by analyzing the effect of gravitational lensing, where light from the galaxies behind Abell 1689 is distorted by intervening matter within the cluster. The researchers used the observed positions of 135 lensed images of 42 background galaxies to calculate the location and amount of dark matter in the cluster. They superimposed a map of these inferred dark matter concentrations, tinted in blue, on an image of the cluster taken by Hubble’s Advanced Camera for Surveys. If the cluster’s gravity came only from the visible galaxies, the lensing distortions would be much weaker. The map reveals that the densest concentration of dark matter is in the core of the cluster. Abell 1689 resides 2.2 billion light-years from Earth. The image was taken in June 2002. Credit: NASA, ESA, D. Coe (NASA Jet Propulsion Laboratory/California Institute of Technology, and Space Telescope Science Institute), N. Benitez (Instituto de Astrofísica de Andalucía, Spain), T Broadhurst (University of the Basque Country, Spain), and H. Ford (Johns Hopkins University)

Dark matter remains one of the biggest mysteries in modern physics. It is clear that it must exist, because without dark matter, for example, the movement of galaxies cannot be explained. But it has never been possible to detect dark matter in an experiment.

Currently, there are many proposals for new experiments: they aim to detect dark matter directly through its scattering from the constituents of atomic nuclei of a detection medium, i.e. protons and neutrons.

A team of researchers, Robert McGehee and Aaron Pierce of the University of Michigan and Gilly Elor of the Johannes Gutenberg University of Mainz in Germany, have now proposed a new candidate for dark matter: HYPER, or “Highly Interactive Particle Relics.”

In the HYPER model, some time after the formation of dark matter in the early universe, the strength of its interaction with normal matter increases abruptly, which on the one hand makes it potentially detectable today and at the same time can explain the abundance of dark matter.

The new diversity in the dark matter sector

Since the search for heavy dark matter particles, or so-called WIMPS, has not yet been successful, the research community is looking for alternative dark matter particles, especially lighter ones. At the same time, phase transitions are generally expected in the dark sector; after all, there are several in the visible sector, the researchers say. But previous studies have tended to neglect them.

“There has not been a consistent model of dark matter for the range of masses that some planned experiments hope to access. However, our HYPER model illustrates that a phase transition can actually help make dark matter more easily detectable.” said Elor, a postdoctoral researcher. in theoretical physics at JGU.

The challenge for a proper model: if dark matter interacts too strongly with normal matter, its (precisely known) amount formed in the early universe would be too small, contradicting astrophysical observations. However, if it occurs in just the right amount, the interaction would be too weak to detect dark matter in current experiments.

“Our central idea, which underlies the HYPER model, is that the interaction changes abruptly once, so that we can have the best of both worlds: the right amount of dark matter and a large interaction so that we can detect it,” McGehee said.

A new model for dark matter

Constraints in the nucleon-mass coupling plane of the mediator due to cooling of HB stars [25] and SN 1987A [12]as well as rare kaon decays [26] (grey shading). Credit: Physical Review Letters (2023). DOI: 10.1103/PhysRevLett.130.031803

And this is how the researchers envision it: In particle physics, an interaction is usually mediated by a specific particle, a so-called mediator, just like the interaction of dark matter with normal matter. Both the formation of dark matter and its detection work through this mediator, with the strength of the interaction depending on its mass: the greater the mass, the weaker the interaction.

The mediator must first be heavy enough for the correct amount of dark matter to form, and then light enough for the dark matter to be detectable. The solution: There was a phase transition after the formation of dark matter, during which the mass of the mediator suddenly decreased.

“So, on the one hand, the amount of dark matter remains constant, and on the other hand, the interaction is driven or strengthened in such a way that the dark matter should be directly detectable,” Pierce said.

The new model covers almost the entire range of parameters of the planned experiments.

“The HYPER model of dark matter can cover almost the entire range that the new experiments make accessible,” Elor said.

Specifically, the research team first considered the maximum cross section of mediator-mediated interaction with the protons and neutrons of an atomic nucleus to be consistent with astrological observations and certain particle physics decays. The next step was to consider whether there was a model for dark matter that would exhibit this interaction.

“And here we came up with the idea of ​​the phase transition,” McGehee said. “We then calculated how much dark matter exists in the universe and then simulated the phase transition using our calculations.”

There are many limitations to take into account, such as a constant amount of dark matter.

“Here, we have to systematically consider and include many scenarios, for example asking the question of whether it is really safe for our mediator not to suddenly lead to the formation of new dark matter, which of course it must not be,” Elor said. . “But in the end, we were convinced that our HYPER model works.”

The research is published in the journal Physical Review Letters.

More information:
Gilly Elor et al, Maximizing Direct Detection with Highly Interactive Particle Relic Dark Matter, Physical Review Letters (2023). DOI: 10.1103/PhysRevLett.130.031803

Provided by the University of Michigan

Citation: A New Model for Dark Matter (2023, Jan 23) Retrieved Jan 23, 2023 from https://phys.org/news/2023-01-dark.html

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