A new model for dark matter

Dark matter remains one of the great mysteries of modern physics. Obviously, it must exist, because without dark matter, for example, the motion of galaxies cannot be explained. But dark matter has never been possible to detect in an experiment.

There are currently many proposals for new experiments: aimed at detecting darkness Thing directly by their scattering from the components of the atomic nuclei of the detection medium, i.e. protons and neutrons.

A team of researchers — Robert McGee and Aaron Pearce of the University of Michigan and Geli Ellor of the Johannes Gutenberg University in Mainz, Germany — has proposed a new dark matter candidate: HYPER, or “Highly Interactive Particulate Relics.”

In the HYPER model, some time after the formation of dark matter in early universeIts interaction with ordinary matter is surprisingly getting stronger – making it possible to detect it today and at the same time explaining the abundance of dark matter.

The new diversity in the dark matter sector

Because the search for heavy dark matter particles, or WIMPS, has not yet led to success, the research community is looking for alternative dark matter particles, especially lighter ones. At the same time, one would generally expect phase transitions In the dark sector – after all, there are many more in the visible sector, the researchers say. But previous studies tend to neglect it.

“There hasn’t been a consistent model of dark matter for the mass range that some planned experiments hope to hit,” said Elor, a postdoctoral researcher. “However, our HYPER model shows that phase transition can actually help make dark matter easier to detect.” . in theoretical physics at JGU.

The challenge for an adequate model: If dark matter interacts strongly with ordinary matter, then the (accurately known) amount of it formed in the early universe would be very small, which contradicts astrophysical observations. However, if produced in the right amount, the interaction would be too weak to detect dark matter in current experiments.

“Our central idea, which underpins the HYPER model, is that the interaction suddenly changes all at once – so we can get the best of both worlds: the right amount of dark matter and a lot of interaction so that we can detect it,” McGee said.

And this is how the researchers conceived it: in particle physics, the interaction is usually mediated by a particular particle, the so-called medium — and so is the interaction of dark matter with ordinary matter. Both the composition of dark matter and the function of detection are detected by this medium, with the strength of the interaction depending on its mass: the greater the mass, the weaker the interaction.

The medium must first be heavy enough for the correct amount of dark matter to be formed, and later light enough so that dark matter can be detected at all. Solution: There was a phase transition after the formation of dark matter, in which the mass of the medium suddenly decreased.

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

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 the new experiments are making available,” Ellor said.

Specifically, the research team first considered the maximum cross-section of the interaction medium with the protons and neutrons of an atomic nucleus to be consistent with astronomical observations and some particle physics decompositions. The next step was to see if there was a model of dark matter that showed this interaction.

“And that’s where we came up with the idea of ​​transition,” McGee said. “We then calculated the amount of dark matter present in the universe and then simulated the phase transition using our calculations.”

There are a slew of limitations to keep in mind, such as a fixed amount of dark matter.

“Here, we have to systematically consider and include several scenarios, for example, asking the question whether it is really certain that our medium does not suddenly lead to the formation of dark matterAnd that, of course, doesn’t have to be the case,” Ellor said. But in the end, we were convinced that HYPER Model Works “.

Publication of the research in the journal Physical review letters.