Neutrinos and Antimatter: A Cosmic Mystery

What are Neutrinos?

Neutrinos are subatomic particles that are very similar to electrons, but they do not carry an electric charge. This means they’re not affected by the electromagnetic forces that act on charged particles such as electrons and protons. Neutrinos are affected only by a “weak” sub-atomic force of much shorter range than electromagnetism, and are therefore able to pass through great distances in matter without being affected.

The Antimatter Conundrum

Particles have mirror-world partners called antiparticles, or antimatter. These antimatter particles have the same mass as the matter particles we know, but are opposite in every other way. All of the quantum properties (such as spin and charge) are reversed. An antimatter world would look much like our own, with antiprotons and antineutrons combining with positrons (the antimatter version of an electron) to form antiatoms and even antimolecules.

The Neutrino-Antineutrino Paradox

One of the biggest questions that physicists ask is whether neutrinos and their antimatter partners, antineutrinos, are actually the same thing. If neutrinos and antineutrinos don’t function like normal matter and antimatter, they could help explain how all of this matter survived and evolved to the universe we see today.

The Matter-Antimatter Asymmetry

The reason why there is more matter than antimatter in the universe is one of the greatest mysteries of modern physics. The Big Bang, which occurred about 13.8 billion years ago, should have created equal amounts of matter and antimatter. However, the universe we see today is made almost entirely out of matter.

When a particle and its antiparticle meet, they annihilate each other, disappearing in a burst of light. If there had ever been an equal amount of antimatter, everything in the universe would have been annihilated. Yet, we exist, which means there must have been a slight asymmetry in favor of matter over antimatter in the early universe.

Scientists believe that in the very hot and dense state shortly after the Big Bang, there must have been processes that gave preference to matter over antimatter. This created a small surplus of matter, and as the universe cooled, all the antimatter was destroyed, or annihilated, by an equal amount of matter, leaving a tiny surplus of matter.

Experiments have shown that certain particles known as mesons can spontaneously turn into their anti-meson and vice versa. But this can happen more in one direction than the opposite one—creating more matter than antimatter over time. This could be one of the mechanisms contributing to the asymmetry between matter and antimatter.

However, this doesn’t fully explain the observed asymmetry. The exact processes that caused this imbalance are still unknown and are a subject of ongoing research in particle physics.

Neutrinos: The Key to Antimatter’s Rarity?

Mounting evidence suggests that neutrinos may be key to why antimatter is rare. Tiny subatomic particles called neutrinos could help answer a really big question: why anything exists at all. A new result reaffirms earlier hints that neutrinos behave differently than their antimatter counterparts, antineutrinos. If confirmed, the particles’ divergence could help reveal how the universe avoided becoming an empty wasteland. The cosmos is filled with matter. Its counterpart, antimatter, is much less common. But in the newborn cosmos, both existed in equal measure. Since matter and antimatter particles annihilate each other when they get together, that should have left the cosmos filled with nothing but energy. For the universe to have formed as we know it, something must have tipped the balance toward matter. The new result, if reinforced by future measurements, would support a long-held hunch that neutrinos are key to explaining how matter got the upper hand.