Axions: Another Dark Matter Candidate Not Found

The endless quest for a dark matter particle comes up empty again.
Too much is invested in the search to give up.

 

How would scientists ever explain the millions spent on a failed quest? The search must go on!

Narrowing the theoretical space in which to look for dark matter (CERN via Phys.org, 5 Dec 2022). Will dark matter particle searches be looked back on as the equivalent of 21st century alchemy? One of the favorite images for the philosopher’s stone is the axion, a theoretical particle that has never been seen. But cosmologists are making progress: they know where it is not.

Axions are the favorite dark matter candidate particles for some researchers. It would sure be handy to find them.

Hypothetical particles called axions could solve two enigmas at once. They could account for dark matter, the mysterious substance that is thought to make up most of the matter in the universe, and they could also explain the puzzling symmetry properties of the strong force that holds protons and neutrons together in atomic nuclei.

CERN lab built a CAST-CAPP Resonator to look for the hypothetical axions (see Nature paper from October 19).

Any luck? One can’t say they didn’t try:

The CAST researchers scanned this 660 MHz band of frequencies in steps of 200 kHz for 4124 hours, from 12 September 2019 to 21 June 2021, and isolated known background signals such as the 5 GHz Wireless Local Area Network (WLAN), but did not pick up any signal coming from axions. However, the CAST-CAPP data places new bounds on the maximum strength of the interaction of axions with photons for axion masses of 19.74 to 22.47 microelectronvolts, narrowing down the space in which to look for axion dark matter.

A previous axion search failed also:

The new bounds are complementary to results from previous axion searches, including those from another CAST haloscope, RADES, which took data in 2018.

How long will the public put up with excuses that “we’re getting warmer” before asking for their money back? Researchers stick to a tried-and-true strategy: promising the answer in futureware. The public doesn’t want them to give up now, do they?

The hunt for dark matter continues. Tune in to this station again to check for updates from CAST-CAPP or from other dark-matter investigations taking place at CERN, such as searches for dark matter that may be produced at the Large Hadron Collider.

If axions aren’t found, the other teams can keep looking for WIMPS or MACHOS or other exotic particles that haven’t even been dreamed up yet.

Researchers say space atomic clocks could help uncover the nature of dark matter (Kavli Institute via Phys.org, 5 Dec 2022). A team of researchers thinks that dark matter might be detected through observations of Mercury. Assuming some places have more of it than others, they believe that an atomic clock on a spacecraft might indirectly detect its presence. First, they assure the public it exists. They even know its percentage.

Dark matter makes up more than 80% of mass in the universe, but it has so far evaded detection on Earth, despite decades of experimental efforts. A key component of these searches is an assumption about the local density of dark matter, which determines the number of dark matter particles passing through the detector at any given time, and therefore the experimental sensitivity.

They claim they can do it. They just need the spacecraft. What would that cost? They don’t say.

“Long-distance space missions, including possible future missions to Mars, will require exceptional timekeeping as would be provided by atomic clocks in space. A possible future mission, with shielding and trajectory very similar to the Parker Solar Probe, but carrying an atomic clock apparatus, could be sufficient to carry out the search,” said Eby.

Why They Believe

Most precise accounting yet of dark energy and dark matter (Harvard Gazette, 19 Oct 2022). This article from October shows why cosmologists are convinced that dark matter is out there. By measuring light from supernovas, and redshifts from galaxies, they infer that there is too much motion for plain ordinary gravity to explain. This is called the “Hubble Tension.” It represents a discrepancy between theory and observations.

Harvard’s Pantheon+ project and a database called SHoES have measured more supernovas than ever.

Now, Brout and Scolnic and their new Pantheon+ team have added some 50 percent more supernovae data points in Pantheon+, coupled with improvements in analysis techniques and addressing potential sources of error, which ultimately has yielded twice the precision of the original Pantheon.

Taking the data as a whole, the new analysis holds that 66.2 percent of the universe manifests as dark energy, with the remaining 33.8 percent being a combination of dark matter and matter.

Any luck?

“We thought it would be possible to find clues to a novel solution to these problems in our dataset, but instead we’re finding that our data rules out many of these options and that the profound discrepancies remain as stubborn as ever,” says Brout.

The Pantheon+ results could help point to where the solution to the Hubble tension lies. “Many recent theories have begun pointing to exotic new physics in the very early universe, however such unverified theories must withstand the scientific process and the Hubble tension continues to be a major challenge,” says Brout.

And so modern cosmology is stuck with a nearly unbelievable tension: most of the universe, according to leading theories by the world’s experts, consists of Mysterious Unknown STuff that MUST be there. Too much is invested in accepted theories to give up now.

We want to see the stuff. How much more time and money do they get? When will the time come for a paradigm shift?

It’s worth mentioning the distinction between “cold dark matter” in big bang theory and dark matter inferred from galaxy motions. The former is like a fudge factor used to make the theory work. The latter is inferred from rotation curves of spiral galaxies; some creation scientists believe that dark matter is the only explanation. Galaxy curves are often anomalous. Instead of falling off near the edges as expected, the curves stay relatively flat with distance from the center, implying that hidden matter is making the outer portions move faster than expected from Keplerian dynamics. Also, the motions of galaxies in clusters seem to imply more hidden mass than detected in visible light. How these two different categories of dark matter overlap is open to debate.

The point in my questioning of the dark matter hypothesis is that materialist big-bang cosmologists have been positing some kind of “particle” (axions, WIMPs, peculiar neutrinos, etc) or non-luminous matter (brown dwarfs, MACHOs, etc) for decades now, but every detection attempt fails. Many of the latest detectors are extremely expensive and elaborate, but they never find anything. How much longer do they get? If they use taxpayer money, there needs to be accountability. Let them find wealthy donors like the SETI people did to keep up the quest, or else admit defeat and try another theory.