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. But it surely has by no means been potential to detect dark matter in an experiment.

At present, there are various proposals for brand new experiments: They goal to detect darkish matter instantly by way of its scattering from the constituents of the atomic nuclei of a detection medium, i.e., protons and neutrons.

A workforce 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 doubtlessly detectable immediately and on the identical 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 neighborhood is searching for various dark matter particles, particularly lighter ones. On the identical time, one generically expects phase transitions at midnight sector—in any case, 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. Nevertheless, our HYPER mannequin illustrates {that a} phase transition can truly assist make the dark matter extra simply detectable,” mentioned Elor, a postdoctoral researcher in theoretical physics at JGU.

The problem for an appropriate mannequin: If dark matter interacts too strongly with regular matter, its (exactly identified) quantity shaped within the early universe could be too small, contradicting astrophysical observations. Nevertheless, 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 are able to have the very best of each worlds: the correct amount of dark matter and a big interplay so we’d detect it,” McGehee mentioned.

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 by way of 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 gentle 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 immediately decreased.

“Thus, on the one hand, the quantity of dark matter is saved fixed, and then again, the interplay is boosted or strengthened in such a approach that dark matter must be instantly detectable,” Pierce mentioned.

New mannequin covers virtually the total parameter vary of deliberate experiments

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

Particularly, the analysis workforce first thought-about the utmost cross part of the mediator-mediated interplay with the protons and neutrons of an atomic nucleus to be in step with astrological observations and sure particle-physics decays. The following 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 mentioned. “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 amazing many constraints to contemplate, corresponding to a continuing quantity of dark matter.

“Right here, we’ve got to systematically take into account and embody very many situations, for instance, asking the query whether or not it’s actually sure that our mediator doesn’t immediately result in the formation of recent dark matter, which after all should not be,” Elor mentioned. “However ultimately, we had been satisfied that our HYPER model works.”

The analysis is revealed within the journal Bodily Evaluation Letters.