Scientists said this particle was up to no good. Turns out, it could be why we exist

A study has theorised that one particle that has been overlooked and dismissed as not being important for the longest time could actually be why the universe exists in the first place. According to a paper published in Physical Review Letters, this rarely studied particle is called the decoupled heavy neutrino.

Two theoretical physicists, one from the University of Southampton and the other from the Indian Institute of Technology Kanpur, have proposed that this forgotten particle played a vital role in shaping the conditions in the early universe. The decoupled heavy neutrino rarely interacts with the rest of the universe and is high in mass. This has led scientists to term it irrelevant.

Mystery of matter and antimatter

But when taken into consideration, it solves a huge mystery about the universe. After the Big Bang happened, for each particle of matter created, a corresponding anti–particle should have also been born. When they come in contact, they both destroy each other, releasing radiation. But the problem is that the universe is dominated by matter.

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"This asymmetry is crucial for our existence, as the presence of matter allows for the formation of stars, planets, and ultimately life, while the scarcity of antimatter raises questions about why it is so rare," says Dr Rishav Roshan, co-author of the study. The team says that the driving force behind this matter–antimatter asymmetry and why we exist is this particular neutrino.

Universe expanded because of it

The duo states in the study that since this neutrino interacts less and decays relatively slowly, it could have contained more energy than all the radiation around it for some time. This would have led the universe to expand rapidly and changed the temperature at which matter and antimatter were forming. "By affecting the interactions and decays of particles during the early universe, these neutrinos can help favour the production of matter over antimatter," Dr Roshan says.

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Their study showed that decoupled heavy neutrinos could trigger matter and antimatter to be slightly imbalanced. They say that even a tiny imbalance, just one extra particle of matter for every billion, was enough for the leftover material to survive annihilation and form everything in the universe today.

The duo admits that this is merely a theory for now. However, they are confident that the proof for this suggestion would be available soon. "This theory could be tested experimentally through upcoming gravitational wave detectors and particle physics experiments," he said.