A new model for dark matter

A new model for dark matter

This image from NASA’s Hubble Space Telescope shows the distribution of dark matter at the center of the giant galaxy cluster Abell 1689, containing around 1,000 galaxies and trillions of stars. Dark matter is a form of invisible matter that accounts for most of the mass in the universe. Hubble cannot see dark matter directly. Astronomers deduced its location by analyzing the effect of gravitational lensing, where light from galaxies behind Abell 1689 is distorted by matter intervening in the cluster. The researchers used the observed positions of 135 lens images of 42 background galaxies to calculate the location and amount of dark matter in the cluster. They overlaid a map of these inferred dark matter concentrations, tinted blue, over an image of the cluster taken by Hubble’s Advanced Camera for Surveys. If the gravity of the cluster only came from the visible galaxies, the lensing distortions would be much weaker. The map reveals that the densest concentration of dark matter is at the heart 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 (Institute of Astrophysics of Andalusia, Spain) , T. Broadhurst (University of the Basque Country, Spain) and H. Ford (Johns Hopkins University)

Dark matter remains one of the greatest mysteries of modern physics. Clearly it must exist, because without dark matter, for example, the motion 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 the question directly via its diffusion from the constituents of the atomic nuclei of a detection medium, namely protons and neutrons.

A team of researchers – Robert McGehee and Aaron Pierce from the University of Michigan and Gilly Elor from Johannes Gutenberg University 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 primitive universethe strength of its interaction with normal matter increases sharply, which on the one hand makes it potentially detectable today and at the same time may explain the abundance of dark matter.

The New Diversity in the Dark Matter Sector

Since the search for heavy dark matter particles, or WIMPS, has yet to come to fruition, the research community is searching for alternative dark matter particles, especially lighter ones. At the same time, we generically expect phase transitions in the dark sector – after all, there are several in the visible sector, the researchers say. But previous studies have tended to overlook them.

“There has not been a consistent dark matter model for the mass range 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 suitable model: if dark matter interacts too strongly with normal matter, its (precisely known) quantity formed in the early universe would be too small, which would contradict astrophysical observations. However, if produced in the right amount, the interaction would conversely 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. “, said McGehee.

A new model for dark matter

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

And here’s how the researchers think about 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 via this mediator, 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 right amount of dark matter to be formed and then light enough for the dark matter to be detectable. The fix: There was a phase transition after the formation of dark matter, during which the mass of the mediator suddenly decreased.

“Thus, on the one hand, the amount of dark matter is kept constant, and on the other hand, the interaction is stimulated or enhanced in such a way that dark matter should be directly detectable,” said Pierce.

The new model covers almost the entire parameter range of the planned experiments

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

Specifically, the research team first considered that the maximum cross section of mediator-mediated interaction with protons and neutrons of an atomic nucleus was consistent with astrological observations and certain decays in the physics of particles. The next step was to determine if there was a model of dark matter exhibiting this interaction.

“And here we got the idea of ​​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 constraints to consider, such as a constant amount of dark matter.

“Here we have to systematically consider and include very many scenarios, for example by asking ourselves the question whether it is really certain that our mediator does not suddenly lead to the formation of new black matterwhich of course doesn’t have to be,” Elor said. “But in the end, we were convinced that our HYPER model works.”

The research is published in the journal Physical examination letters.

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

Quote: 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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