New particle links dark matter with missing antimatter

Physicists in the US and Canada have proposed a new particle that could solve two important mysteries of modern physics: what is dark matter and why is there much more matter than antimatter in the universe?

The yet-to-be-discovered “X” particle is expected to decay mostly to normal matter, whereas its antiparticle is expected decay mostly to “hidden” antimatter. The team claims that its existence in the early universe could explain why there is more matter than antimatter in the universe – and that dark matter is in fact hidden antimatter.

Dark matter is a mysterious substance that appears to make up about 80% of the material universe. Although its existence can be inferred from its gravitational pull on normal matter, physicists have yet to detect it directly and therefore don’t know what it is made of. Antimatter, on the other hand, is easy to create and study in the lab. However, the Standard Model of particle physics cannot explain why antimatter is so rare in a universe that is dominated by matter – a mystery called baryon asymmetry.

Hypothetical and hidden

Now, Hooman Davoudiasl of Brookhaven National Laboratory and colleagues at TRIUMF and the University of British Columbia have proposed a new particle dubbed X that could solve both of these mysteries. X has a mass of about 1000 GeV – making it about a thousand times heavier than a proton. This particle can decay to a neutron or to two hypothetical hidden particles called Y and Φ. Both hidden particles would have masses of about 2–3 GeV. Its antiparticle, anti-X, decays to an antineutron or to the pair anti-Y and anti-Φ.

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