September 28, 2023


The Internet Generation

A Super Sensitive Dark-Matter Search Yields Strange Results

As the WIMP search saved coming up vacant, XENON scientists recognized numerous years ago that they could use their experiment to search for other varieties of mysterious particles that might pass by the detector: particles that bang into an electron rather than a xenon nucleus.

They used to treat these “electronic recoils” as background sounds, and in fact a lot of of these situations are triggered by mundane sources this sort of as radioactive direct and krypton isotopes. But following creating improvements to drastically cut down their background contaminations more than the years, the scientists identified that they could appear for signals in the low-stage sounds.

In their new assessment, the physicists examined electronic recoils in the to start with year’s really worth of XENON1T knowledge. They anticipated to see around 232 of these recoils, triggered by known sources of background contamination. But the experiment saw 285—a surplus of fifty three that signifies an unaccounted-for supply.

The crew saved the obtaining below wraps for about a calendar year. “We have been working and working and seeking to realize,” Aprile reported. “I indicate, these lousy students!” Immediately after rejecting all probable sources of error they could assume of, the scientists came up with three explanations that would suit the dimension and condition of the bump in their knowledge plots.

Very first and potentially most fascinating is the “solar axion,” a hypothetical particle created inside of the sunlight that would be very similar to a photon but with a very small volume of mass.

Any axions created not long ago in the sunlight could not be the darkish make a difference that has shaped the cosmos considering that primordial instances. But if the experiment has detected solar axions, then it indicates axions exist. “Such an axion could also be created in the early universe and then would make up some part of darkish make a difference,” reported Peter Graham, a particle physicist at Stanford University who has theorized about axions and strategies to detect them.

Scientists reported the strength of solar axions inferred from XENON1T’s bump does not suit with the easiest products of axion darkish make a difference, but far more complicated products can most likely reconcile them.

A different risk is that neutrinos—the most mysterious of the known particles of nature—might have significant magnetic times, this means they’re like little bar magnets. This kind of a residence would make it possible for them to scatter with electrons at an improved rate, conveying the surplus of electronic recoils. Graham reported neutrinos possessing a magnetic minute “would also be really fascinating considering that it implies new physics beyond the Common Product.”

But it is also probable that trace amounts of tritium, a rare hydrogen isotope, are present in the xenon tank, and that their radioactive decays produce electronic recoils. This risk “can be neither verified nor excluded,” the XENON1T crew wrote in their paper.

Exterior scientists say there are “not crimson, but orange flags,” as Falkowski set it, that position to the unexciting reply. Most importantly, if the sunlight produces axions, then all stars do. These axions pull a smaller volume of strength absent from the star, like steam carrying absent the strength of a boiling kettle. In really incredibly hot stars like crimson giants and white dwarves, the place axion production must be greatest, this strength loss would be more than enough to interesting the stars down. “A white dwarf would develop so a lot of axions that we would not see incredibly hot white dwarves all-around these days like we do,” reported Zurek.

Neutrinos with significant magnetic times have been likewise disfavored: In comparison to typical neutrinos, far more of them would be spontaneously created inside of stars, sapping absent far more of the stars’ strength and cooling down incredibly hot stars far more than is noticed.

But that logic might be flawed, or some other particle or effect might describe XENON1T’s bump. Thankfully the physics community will not have to hold out very long for responses XENON1T’s successor, the XENONnT experiment—which will observe for recoils in 8.3 metric tons of xenon—is on monitor to begin knowledge selection later this calendar year. “If the surplus is there and at the exact same stage,” Grandi reported, then “we anticipate to be able to discriminate among [the alternatives] in a handful of months of knowledge taking.”

“One thing is very clear,” reported Juan Collar, a darkish make a difference physicist at the University of Chicago who is not associated in the experiment. “The XENON system continues to trailblaze in the darkish make a difference subject. The most delicate experiment will be the to start with to operate into the unanticipated, and XENON continues to keep a stable grip on that prized pole placement.”

Unique story reprinted with permission from Quanta Journal, an editorially impartial publication of the Simons Basis whose mission is to increase community knowing of science by masking study developments and traits in mathematics and the actual physical and lifetime sciences.

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