A brand new mannequin for darkish matter


This NASA Hubble House Telescope picture reveals the distribution of darkish matter within the heart of the enormous galaxy cluster Abell 1689, containing about 1,000 galaxies and trillions of stars. Darkish matter is an invisible type of matter that accounts for many of the universe’s mass. Hubble can’t see the darkish matter immediately. Astronomers inferred its location by analyzing the impact of gravitational lensing, the place mild from galaxies behind Abell 1689 is distorted by intervening matter throughout the cluster. Researchers used the noticed positions of 135 lensed photos of 42 background galaxies to calculate the situation and quantity of darkish matter within the cluster. They superimposed a map of those inferred darkish matter concentrations, tinted blue, on a picture of the cluster taken by Hubble’s Superior Digicam for Surveys. If the cluster’s gravity got here solely from the seen galaxies, the lensing distortions could be a lot weaker. The map reveals that the densest focus of darkish matter is within the cluster’s core. Abell 1689 resides 2.2 billion light-years from Earth. The picture was taken in June 2002. Credit score: NASA, ESA, D. Coe (NASA Jet Propulsion Laboratory/California Institute of Expertise, and House Telescope Science Institute), N. Benitez (Institute of Astrophysics of Andalusia, Spain), T. Broadhurst (College of the Basque Nation, Spain), and H. Ford (Johns Hopkins College)

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

Presently, there are numerous proposals for brand new experiments: They intention 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 darkish matter: HYPER, or “HighlY Interactive ParticlE Relics.”

Within the HYPER mannequin, a while after the formation of darkish 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 at the moment and on the identical time can clarify the abundance of darkish matter.

The brand new variety at the hours of darkness matter sector

Because the seek for heavy darkish matter particles, or so-called WIMPS, has not but led to success, the analysis group is searching for various darkish matter particles, particularly lighter ones. On the identical time, one generically expects part transitions at the hours of darkness 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 darkish matter mannequin for the mass vary that some deliberate experiments hope to entry. Nonetheless, our HYPER mannequin illustrates {that a} part transition can truly assist make the darkish matter extra simply detectable,” mentioned Elor, a postdoctoral researcher in theoretical physics at JGU.

The problem for an acceptable mannequin: If darkish matter interacts too strongly with regular matter, its (exactly identified) quantity shaped within the early universe could 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 darkish matter in present-day experiments.

“Our central thought, which underlies the HYPER mannequin, is that the interplay modifications abruptly as soon as—so we are able to have the most effective of each worlds: the correct amount of darkish matter and a big interplay so we’d detect it,” McGehee mentioned.

A new model for dark matter
Constraints within the mediator mass-nucleon coupling airplane from cooling of HB stars [25] and SN 1987A [12], in addition to uncommon kaon decays [26] (grey shading). Credit score: Bodily Evaluation Letters (2023). DOI: 10.1103/PhysRevLett.130.031803

And that is how the researchers envision it: In particle physics, an interplay is normally mediated by a particular particle, a so-called mediator—and so is the interplay of darkish matter with regular matter. Each the formation of darkish 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 darkish matter is shaped and later mild sufficient in order that darkish matter is detectable in any respect. The answer: There was a part transition after the formation of darkish matter, throughout which the mass of the mediator all of the sudden decreased.

“Thus, on the one hand, the quantity of darkish matter is saved fixed, and however, the interplay is boosted or strengthened in such a manner that darkish matter ought to be immediately detectable,” Pierce mentioned.

New mannequin covers nearly the complete parameter vary of deliberate experiments

“The HYPER mannequin of darkish matter is ready to cowl nearly the whole vary that the brand new experiments make accessible,” Elor mentioned.

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 in step with astrological observations and sure particle-physics decays. The following step was to think about whether or not there was a mannequin for darkish matter that exhibited this interplay.

“And right here we got here up with the thought of the part transition,” McGehee mentioned. “We then calculated the quantity of darkish matter that exists within the universe after which simulated the part transition utilizing our calculations.”

There are a fantastic many constraints to think about, reminiscent of a relentless quantity of darkish matter.

“Right here, we’ve to systematically contemplate and embrace very many eventualities, for instance, asking the query whether or not it’s actually sure that our mediator doesn’t all of the sudden result in the formation of recent darkish matter, which after all should not be,” Elor mentioned. “However ultimately, we had been satisfied that our HYPER mannequin works.”

The analysis is printed within the journal Bodily Evaluation Letters.

Extra data:
Gilly Elor et al, Maximizing Direct Detection with Extremely Interactive Particle Relic Darkish Matter, Bodily Evaluation Letters (2023). DOI: 10.1103/PhysRevLett.130.031803

A brand new mannequin for darkish matter (2023, January 23)
retrieved 23 January 2023
from https://phys.org/information/2023-01-dark.html

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