The more definitive mass means that the most common type of experiment to detect these elusive particles — a microwave resonance chamber containing a strong magnetic field, in which scientists hope to snag the conversion of an axion into a faint electromagnetic wave — won’t be able to detect them, no matter how much the experiment is tweaked. The chamber would have to be smaller than a few centimeters on a side to detect the higher-frequency wave from a higher-mass axion, Safdi said, and that volume would be too small to capture enough axions for the signal to rise above the noise.
“Our work provides the most precise estimate to date of the axion mass and points to a specific range of masses that is not currently being explored in the laboratory,” he said. “I really do think it makes sense to focus experimental efforts on 40 to 180 μeV axion masses, but there’s a lot of work gearing up to go after that mass range.”
One newer type of experiment, a plasmonic haloscope, which looks for axion excitations in a metamaterial — a solid-state plasma — should be sensitive to an axion particle of this mass, and could potentially detect one.
“The basic studies of these three-dimensional arrays of fine wires have worked out amazingly well, much better than we ever expected,” said Karl van Bibber, a UC Berkeley professor of nuclear engineering who is building a prototype of the plasmonic haloscope while also participating in a microwave cavity axion search called the HAYSTAC experiment. “Ben’s latest result is very exciting. If the post-inflation scenario is right, after four decades, discovery of the axion could be greatly accelerated.”
If axions really exist.
The work was published today (Feb. 25) in the journal Nature Communications.
Axion top candidate for dark matter
Dark matter is a mysterious substance that astronomers know exists — it affects the movements of every star and galaxy — but which interacts so weakly with the stuff of stars and galaxies that it has eluded detection. That doesn’t mean dark matter can’t be studied and even weighed. Astronomers know quite precisely how much dark matter exists in the Milky Way Galaxy and even in the entire universe: 85% of all matter in the cosmos.
Safdi’s colleagues include Malte Buschmann of Princeton; MIT postdoctoral fellow Joshua Foster; Anson Hook of the University of Maryland; and Adam Peterson, Don Willcox and Weiqun Zhang of Berkeley Lab’s Center for Computational Sciences and Engineering. The research was largely funded by the U.S. Department of Energy through the Exascale Computing Project (17-SC-20-SC) and through the Early Career program (DESC0019225).