Two papers published this week show the puzzling origins and possible uses of antimatter, a form of matter that turns the rules governing ordinary matter on their head.
Another paper, published today in JCAP, found that antinuclei from cosmic rays may be indicative of some form of dark matter. In a separate paper, published earlier this week in AIP Advances, the researchers describe how to detect nuclear reactor locations and activity using antineutrinos produced by nuclear reactions at the facilities.
Antimatter is important because it can help explain fundamental cosmic mysteries, such as why the universe is made of matter instead of an equal mixture of matter and antimatter. These studies are part of a larger effort to analyze the great mysteries of physics, including the nature of dark matter, physics at very small scales, and perhaps the origins of the universe itself.
Despite its name, antimatter is actually matter. It has a lot. Antimatter refers to a group of particles that have opposite electrical charges to their normal counterparts. You’ve heard of electrons (negatively charged) and protons (positively charged); antimatter’s counterparts are positrons (positively charged) and antiprotons (negatively charged).
Although there are differences in particle collisions, antimatter is not a complete stranger to the fundamental energy. Last year, a team of physicists discovered that antimatter responds to gravity in the same way as normal matter, a finding that confirms both Einstein and the Standard Model of Particle Physics.
Something similar to the concept of “antimatter” you might have in your head is dark matter—which also has mass—but it’s invisible to every type of detector that mankind has invented so far. Scientists know that dark matter exists because its gravitational effects are visible, even though the particles (or particles!) involved cannot be directly observed.
Antimatter remains a subject of confusion (sorry, bad pun) for several reasons. As described by Gizmodo in 2022:
The universe shook about 14 billion years ago, with a big bang that should have created equal amounts of matter and antimatter. But look around you, or at the latest Webb telescope images: We live in a universe dominated by matter. A prominent question in physics is what happens to all antimatter.
Antimatter and dark matter go hand in hand in a recent JCAP paper, which states that the amount of antimatter detected by the experiment is higher than it should be—and they believe that dark matter is to blame.
Several different particles (and other, rarer objects) have been posited as carrying dark matter. Among them: axions, a particle called laundry detergent; Massive Compact Halo Objects, or MACHOs; dark photons, which despite their axion-like names are a somewhat deceptive version of light; and primordial black holes, which are tiny black holes born at the beginning of the universe, floating in space.
Recent research has focused on another species—Weakly Interacting Massive Particles, or WIMPs—as the culprit. The theory is that when WIMPs collide, they sometimes annihilate—destroy each other—and release energy and particles of matter and antimatter.
In the above-mentioned 2022 study, a team of physicists using the ALICE experiment at CERN found that antimatter can easily travel through our galaxy instead of being extinguished by interstellar matter, a good conclusion for the discovery of antinuclei like AMS-02. to explore the International Space Station.
“Theoretical predictions suggest that, although cosmic rays can produce antiparticles by interacting with gas in the interstellar medium, the number of antinuclei, especially antihelium, should be very low,” said Pedro De la Torre Luque, a physicist at -Institute of Theoretical. Physicists in Madrid and lead author of the JCAP paper, in the release of SISSA Medialab.
“We expected to find one antihelium event every few decades, but the ten or so antihelium events observed by AMS-02 are many orders of magnitude higher than predictions based on standard cosmic-ray interactions,” De la Torre said. Luke. “That’s why these antinuclei are a plausible clue to WIMP destruction.”
However, De la Torre Luque added that WIMPs can only account for the amount of antihelium-3—one isotope of antimatter detected by AMS-02—and found no amounts of the rarer, heavier antihelium-4. In other words, even if WIMPs are responsible for dark matter, it doesn’t tell the whole story.
WIMPs may be responsible for the detection of antimatter collected by detectors in space. But regardless of the question of dark matter — which will take a long time to answer — the design of an antimatter-sniffing detector to monitor reactors on Earth shows practical use in the here and now. Together, these discoveries of antimatter could provide new ways to harness the strange properties of the universe for practical use, while also helping us better understand both the universe and our own planet.
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