Reports of 10 antihelium nuclei colliding with the ISS have inspired theoretical physicists to propose ideas that extend beyond current scientific models.
Although a small cluster of cosmic particles might not seem particularly remarkable at first glance, the signs of an antihelium "shower" are strange enough for researchers to treat the event as a downpour in a desert. A study published in Physical Review highlights this.
In a recently published analysis, scientists from the Perimeter Institute for Theoretical Physics in Canada and Johns Hopkins University in the United States argue for considering physics beyond the Standard Model, suggesting the involvement of dark matter.
Since 2011, the Alpha Magnetic Spectrometer (AMS-02) has been aboard the International Space Station and has recorded over 200 billion events related to cosmic radiation. Most of the detected particles were ordinary, but some yet-to-be-published reports indicate that ten of them were quite atypical—they consisted of pairs of antiprotons coupled with one or two antineutrons.
Every elementary particle of "ordinary" matter, such as electrons, neutrinos, and quarks, has a corresponding twin with the same properties but opposite charge—an antiparticle. Antiparticles, such as positrons, antineutrinos, and antiquarks, are believed to have been produced in the Big Bang in the same quantity as electrons, neutrinos, and quarks, which would have annihilated each other. The fact that the universe consists of a far greater variety of matter forms than electromagnetic radiation suggests that humans do not fully understand the balance of primordial matter and antimatter.
Just as scientists produce antimatter using particle accelerators, nature continues to release antiprotons and antineutrons during high-energy catastrophes. Some of these particles evade annihilation, travel through space, and are detected on Earth or near it.
The AMS-02 data included antiprotons and antineutrons in the form of antihelium nuclei—a rare combination that requires antiparticles to move slowly and be tightly packed, allowing subatomic particles to combine.
Interestingly, for every antihelium nucleus with two antineutrons, known as antihelium-4, there were two with one antineutron: antihelium-3. Relying solely on existing physics, scientists calculated an isotope ratio of 10,000 to one.
What generated two samples of this antimatter isotope and sent them our way differed from known processes. The initial conditions required the subatomic building blocks to move incredibly slowly before being ejected into space. One possibility could be the decay of a yet-unknown particle, which could even qualify as dark matter.
Researchers suggest that an incredibly hot concentration of rapidly growing plasma, originating from known particles, could provide both the push and the correct ratio of antihelium nuclei.
Although such "fireballs" have never been observed, they could arise from collisions between clumps of dark matter that contain a sufficient amount of antiquarks.
The second potential scenario involves so-called "dark dwarfs." These hypothetical balls of dark photons, dark electrons, and dark neutrons could also collide and create conditions capable of emitting antihelium in the required ratio.
No model has been fully developed; it consists of a complex dynamics that fuels much discussion about potential details. Dark matter itself is yet to be confirmed as a material phenomenon, let alone its properties.
However, even these highly speculative models may contain the seeds of groundbreaking discoveries. New data from AMS-02 might yet gather information that provides another perspective on the origins of this strange antihelium "rain."
Source: Science Alert
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