A new model for dark matter

Darkish matter stays one of many biggest mysteries of recent physics. It’s clear that it should exist, as a result of with out dark matter, for instance, the movement of galaxies can’t be defined. Nevertheless it has by no means been potential to detect dark matter in an experiment.

At the moment, there are various proposals for brand spanking new experiments: They purpose to detect darkish matter immediately through its scattering from the constituents of the atomic nuclei of a detection medium, i.e., protons and neutrons.

A group of researchers—Robert McGehee and Aaron Pierce of the College of Michigan and Gilly Elor of Johannes Gutenberg College of Mainz in Germany—has now proposed a brand new candidate for dark matter: HYPER, or “HighlY Interactive ParticlE Relics.”

Within the HYPER mannequin, a while after the formation of dark matter within the early universe, the power of its interplay with regular matter will increase abruptly—which on the one hand, makes it probably detectable at present and on the similar time can clarify the abundance of dark matter.

The brand new variety within the dark matter sector

Because the seek for heavy dark matter particles, or so-called WIMPS, has not but led to success, the analysis group is on the lookout for different dark matter particles, particularly lighter ones. On the similar time, one generically expects phase transitions at midnight sector—in spite of everything, there are a number of within the seen sector, the researchers say. However earlier research have tended to neglect them.

“There has not been a constant dark matter mannequin for the mass vary that some deliberate experiments hope to entry. Nonetheless, our HYPER mannequin illustrates {that a} phase transition can really assist make the dark matter extra simply detectable,” stated Elor, a postdoctoral researcher in theoretical physics at JGU.

The problem for an acceptable mannequin: If dark matter interacts too strongly with regular matter, its (exactly identified) quantity shaped within the early universe can be too small, contradicting astrophysical observations. Nonetheless, whether it is produced in simply the correct amount, the interplay would conversely be too weak to detect dark matter in present-day experiments.

“Our central concept, which underlies the HYPER mannequin, is that the interplay modifications abruptly as soon as—so we will have the very best of each worlds: the correct amount of dark matter and a big interplay so we would detect it,” McGehee stated.

And that is how the researchers envision it: In particle physics, an interplay is normally mediated by a selected particle, a so-called mediator—and so is the interplay of dark matter with regular matter. Each the formation of dark matter and its detection perform through this mediator, with the power of the interplay relying on its mass: The bigger the mass, the weaker the interplay.

The mediator should first be heavy sufficient in order that the right amount of dark matter is shaped and later mild sufficient in order that dark matter is detectable in any respect. The answer: There was a phase transition after the formation of dark matter, throughout which the mass of the mediator all of a sudden decreased.

“Thus, on the one hand, the quantity of dark matter is stored fixed, and however, the interplay is boosted or strengthened in such a approach that dark matter needs to be immediately detectable,” Pierce stated.

New mannequin covers virtually the total parameter vary of deliberate experiments

“The HYPER mannequin of dark matter is ready to cowl virtually the complete vary that the brand new experiments make accessible,” Elor stated.

Particularly, the analysis group first thought of the utmost cross part of the mediator-mediated interplay with the protons and neutrons of an atomic nucleus to be per astrological observations and sure particle-physics decays. The subsequent step was to contemplate whether or not there was a mannequin for dark matter that exhibited this interplay.

“And right here we got here up with the concept of the phase transition,” McGehee stated. “We then calculated the quantity of dark matter that exists within the universe after which simulated the phase transition utilizing our calculations.”

There are an ideal many constraints to contemplate, resembling a continuing quantity of dark matter.

“Right here, now we have to systematically contemplate and embody very many eventualities, for instance, asking the query whether or not it’s actually sure that our mediator doesn’t all of a sudden result in the formation of latest dark matter, which after all should not be,” Elor stated. “However in the long run, we have been satisfied that our HYPER model works.”

The analysis is printed within the journal Bodily Evaluate Letters.