HYPER (Characteristic Interactive Particle Effects) – a new model for dark matter

A phase transition in the early universe alters the strength of the interaction between normal and 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.

Currently, there are many proposals for new experiments: they aim to directly detect dark matter through its scattering from the components of the atomic nuclei of the detection medium, namely 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, sometime after dark matter forms in the early universe, its interaction with ordinary matter suddenly increases in strength — which on the one hand makes it detectable today and at the same time could explain an abundance of darkness. Thing.

This NASA Hubble Space Telescope image shows the distribution of dark matter in 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 makes up most of the mass of the universe. Hubble cannot see dark matter directly. Astronomers inferred its location by analyzing the effect of gravitational lensing, in which light from galaxies behind Abell 1689 is distorted by interference of 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 mapped the inferred dark matter concentrations, in blue, to an image of the cluster taken by Hubble’s Advanced Camera for Surveys. If the cluster’s gravity came from only 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 is located 2.2 billion light-years from Earth. Photo taken in June 2002.
Image credit: NASA, ESA, D. Coe (NASA Jet Propulsion Laboratory / California Institute of Technology, Space Telescope Science Institute), N. Benitez (Astrophysical Institute of Andalusia, Spain), T. Broadhurst (University of the Basque Country, Spain) and H Ford (Johns Hopkins University)

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 transitions in the visible sector, the researchers say. But previous studies tend to neglect it.

“There has been no consistent model of dark matter for the mass range that some planned experiments hope to achieve. However, our HYPER model shows that phase transition can actually help make matter Dark ones are easier to detect.

The challenge for a proper model: If dark matter interacts strongly with ordinary matter, then how much (accurately known) 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 envision 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 its detection function occur via this medium, with the strength of the interaction dependent on its mass: the greater the mass, the weaker the interaction.

The medium must first be heavy enough so that the right amount of dark matter is formed and later enough light 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 full range that the new experiments make 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 new dark matter, which of course it does not have to happen,” Ellor said. . “But in the end, we were convinced that our HYPER model worked.”

Publication of the research in the journal Physical review letters.

Reference: “Maximizing Direct Detection Using Highly Interacting Particle Dark Matter” By Jelly Ellor, Robert McGee, and Aaron Pierce, Jan. 20, 2023, Available Here. Physical review letters.
DOI: 10.1103/PhysRevLett.130.031803