Can one particle explain both dark matter and the mysterious origins of matter and antimatter? Some physicists think so. They're calling the as-yet-only-theoretical object the “X particle.” Physicists from Canada's TRIUMF particle-physics facility, the University of British Columbia and Brookhaven National Laboratory laid out their ideas on the X particle in a paper published last month by Physical Review Letters — and since then, the ideas have been picked up by PhysicsWorld magazine as well as Discovery News. (You can read a full draft of the paper on the arxiv.org website.) The concept addresses two of the deep mysteries in modern physics:
- Dark matter: Observations of distant galaxies and galaxy clusters suggest that the matter we can see accounts for about a fifth of their gravitational mass. The other four-fifths is thought to exist in the form of exotic matter than can be detected only by its gravitational effect. So what is that stuff?
- Matter vs. antimatter: Theory dictates that equal amounts of matter and antimatter must have existed at the beginning of the universe — and yet, we see lots of matter and virtually no antimatter in the universe today. What happened to the antimatter, and why did matter win out?