An Even Ghostlier Neutrino May Rule the Universe

Strange “right-handed” neutrinos may be responsible for all the matter in the universe, according to new research.

Why is the universe filled with something other than nothing? Almost all fundamental interactions in physics are exactly symmetrical, meaning that they produce just as much matter as they do antimatter. But the universe is filled with only matter, with antimatter only appearing in the occasional high-energy process.

Obviously something happened to tip the balance, but what?

New research suggests that the answer may lie in the ghostly little particles known as neutrinos.

Neutrinos are beyond strange. There are three varieties, and they each have almost no mass. Additionally, they are also all “left-handed”, which means that their internal spins orient in only one direction as they travel. This is unlike all the other particles, which can orient in both directions.

Physicists suspect that there may be other kinds of neutrinos out there, ones that as yet remain undetected. These “right-handed” neutrinos would be much more massive than the more familiar left-handed ones.

Back in the early universe, these two kinds of neutrinos would have mixed together more freely. But as the cosmos expanded and cooled, this even symmetry broke, rendering the heavy right-handed neutrinos invisible. In the process, the symmetry breaking would separate matter from antimatter.

This could be the exact mechanism needed to explain that primordial mystery of the universe. But the right-handed neutrinos have one more trick up their sleeves.

The researchers behind the paper propose that the right-handed neutrinos didn’t completely disappear from the cosmic scene. Instead, they mixed together to form yet another new entity: the Majoran, a hypothetical kind of particle that is its own anti-particle. The Majoran would still inhabit the cosmos, surviving as a relic of those ancient times.

A massive, invisible particle just hanging around the cosmos? That would be an ideal candidate for dark matter, the mysterious substance that makes up the mass of almost every galaxy.

This means that the interactions between different kinds of neutrinos could explain why all observed neutrinos are left-handed, why there is more matter than antimatter, and why the universe is filled with dark matter.

This is all hypothetical, but definitely worth pursuing. And if we ever discover evidence for right-handed neutrinos, we just might be on the right track to solving a number of cosmological mysteries.