Physics

Another dark matter particle candidate has been ruled out, narrowing the search

Another dark matter particle c...
Researchers have ruled out a certain subset of particles that were possible dark matter candidates, using the Neutron Electric Dipole Moment (nEDM) experiment
Researchers have ruled out a certain subset of particles that were possible dark matter candidates, using the Neutron Electric Dipole Moment (nEDM) experiment
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Researchers have ruled out a certain subset of particles that were possible dark matter candidates, using the Neutron Electric Dipole Moment (nEDM) experiment
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Researchers have ruled out a certain subset of particles that were possible dark matter candidates, using the Neutron Electric Dipole Moment (nEDM) experiment

Scientists searching for the elusive dark matter, which appears to make up 80 percent of the matter in the universe, have managed to narrow down the range of possible suspects. Researchers at the University of Sussex have disproved the existence of certain kinds of axions, particles that are a leading candidate for dark matter, and while it may send physicists back to the drawing board, the hunt can be more focused in future.

Dark matter is a tricky substance to pin down. Since it doesn't interact with electromagnetic radiation, it doesn't reflect light at all and can't be directly observed, but its gravitational effects can still be felt. The movements of stars and galaxies don't make sense based on visible matter alone, leading astronomers in the 1930s to hypothesize that some unseen mass was at play. And scientists have been searching for it ever since.

The list of likely suspects has shrunk over the years. Weakly Interacting Massive Particles (WIMPs) with certain masses have been ruled out by several runs of experiments using the Large Underground Xenon (LUX) detector, and the HADES particle detector determined that dark matter wasn't composed of "dark photons."

Axions however remained a strong candidate. Scientists are trying to not only determine if these hypothetical elementary particles exist, but also what their masses might be. The new study has looked at data gathered by the Neutron Electric Dipole Moment (nEDM) experiment and returned a null result, narrowing down the range of masses that axions could have.

"If axions with the right properties exist it would be possible to detect their presence through this entirely novel analysis of our data," says Philip Harris, head of the nEDM group at the University of Sussex. "We've analysed the measurements we took in France and Switzerland and they provide evidence that axions – at least the kind that would have been observable in the experiment – do not exist. These results are a thousand times more sensitive than previous ones and they are based on laboratory measurements rather than astronomical observations."

In the nEDM experiment, neutrons are trapped in specially designed containers, which are then electrified. The aim is to check whether the high voltage affects the rate at which the neutrons spin, and if that frequency changes over time, it would indicate the presence of axions. Since no such distortions were detected, that means there were no axions within the mass range that the instrument can pick up.

The nEDM experiment was originally run to solve a different cosmological mystery. In the beginning of the Universe, matter and antimatter should have been created in equal amounts, but today matter is common while antimatter is almost non-existent. The experiment was designed to study how this asymmetry came to pass, but the Sussex researchers realized that looking at the data in a different way could reveal the existence of axions.

"In our original experiment we took a single measurement and repeated it many times to determine the average value over a long time," says Harris. "When we're searching for axions, we watch for whether the measurement fluctuates over time with a constant frequency. If so, it would be proof that there had been some interaction between the neutron and the axion. We never saw that."

Although it returned a null result, the scientists point out that axions could still exist, just not with the properties that the nEDM experiment tested for. They might not have been interacting with the neutrons strongly enough, or they may have masses that are larger or smaller than the expected range. Future work will have to look elsewhere.

"This does not fundamentally rule out the existence of axions, but the scope of characteristics that these particles could have is now distinctly limited," says Harris. "The results essentially send physicists back to the drawing board in our hunt for dark matter."

The research was published in the journal Physical Review X.

Source: University of Sussex

9 comments
bill92
If the elusive dark matter is needed to explain Galactic level gravity, maybe need to look closer at emergent theory of gravity.
Bob
The major problem with dark matter and dark energy are the fact that they are being postulated to prop up the current Big bang theory which keeps unraveling. I have always suspected that if the big bang really happened it was probably 50-100 billion years ago. This would have given more time for expansion(no need for the faster than light inflation theory). It would also allow more time for several generations of stars to form and reform to synthesize the heavier elements. If 20% of each generation of stars never went nova and simply burned out, after six or seven generations 90% of the mass of the universe would simply be normal matter composed of the cold cinders of extinct stars. They would no longer be visible but their mass and gravitational effects would still be observed. No inflation, exotic matter or energy explanation needed, just a longer time scale.
mpc755
There is evidence of the smoothly distributed, strongly interacting, supersolid dark matter every time a double-slit experiment is performed, as it is the dark matter that waves.
ProfessorWhat
I don't get why New Atlas keeps perpetuating​ a blatant bias when it comes to the so-called existence of dark matter/energy; just because someone says that there is something there because- doesn't mean there is...
There are several other theoretical models that add up and compute when it comes to things that "dark matter/energy causes" without needing either to function, like how Timescape Cosmology is able demonstrate that the universe may not actually really be exponentially expanding as current mainstream BELIEFS suggests it is.
ljaques
Well, ProfessorFlatEarth. What are scientists supposed to do? Accept your assertion that dark matter isn't real, or continue formulating many hypotheses in an attempt to prove or disprove their own theories? I vote for the latter. It appears that many people in many labs in many places do, and NewsAtlas is one. How is that bias? Looks like open-mindedness to me, and I welcome it. I'm a knowledge seeker, and until we know one way or the other, why not keep seeking knowledge about dark matter? You settled for an answer, and that's fine for you, but we haven't, so it isn't for us. Keep going, Seekers. Fusion, gravity, & FTL travel are just a few things I'd like to see before I crumble to ash.
Chris74
ever play with a gyroscope as a kid? notice how it got "heavier" as you tried to tilt it? how about going really fast in a circle on a merry-go-round? the faster it spun, the heavier you got and the harder it was to hold on? how can you measure gravity sucessfully when its so dependant on kinetic energy-rotation?
as for the universe expanding, thats so easy to explain! Every galaxy is a solar sail and the light from other galaxy's act upon the sails as such.
tim_g.
Knock Knock ... anyone home?
Spiral galaxies in our universe seem to be achieving an impossible feat. The stars in spiral galaxies are rotating with such speed that the gravity signature generated by the observable matter could not possibly hold them together; they should have torn themselves apart long ago. The same is true of galaxies in clusters, which leads scientists to believe that something we cannot see is at work. They think something we have yet to detect directly is giving these galaxies extra mass, generating the extra gravity they need to stay intact. This strange and unobserved matter was named “dark matter. Lack of knowledge to how gravity works at the galactic scale is at the root of the problem. The influence of gravity signature within a spiral galaxy is different than that observed by Newton. 21st century solution and innovation to resolve the problem can be found in the google links below. The principles of atomic gravity are tools used to unify and advance academic research in the natural sciences. The principles describe the method to how the force of gravity is transferred at both the atomic and galactic scale. Innovative Principles of Atomic Gravity- How gravity works! https://docs.google.com/document/d/e/2PACX-1vRTa9BoY64I0KsYrM1y7aRMONd7OrFm5RGIgPGA7PolB8hIXjF66azQOTu2yHWpl3uzw614aX6Ks-9q/pub Zero G flight at the Atomic Scale https://docs.google.com/document/d/e/2PACX-1vRhOSAFyKb9r0kMaEGbLm-skalqF7UAXaqKQDq_RcJCWDAmOQCkbUvIIwih5DALMnqa6p7DzmQxAbzI/pub Hope and faith should not part of the scientific method. Please stop self-interests from marketing dark matter research for more public funding. Play your part in the advancement of scientific knowledge and efficient use of public dollars.
aki009
It's pretty easy to explain dark matter.
When the machines created The Matrix, they made a minor error in the part of the simulation that displays galactic scale objects and phenomena.
JimFox
ProfessorWhat-- you are completely wrong, apparently- dark matter is produced in thunderstorms-- https://newatlas.com/lightning-gamma-rays-antimatter/52312/