Particles called axions could reveal how matter conquered the universe
Chalk up a potential third win for hypothetical particles called axions. If the subatomic particles exist, they could solve two pressing puzzles of particle physics: the source of the dark matter that fills galaxies with invisible mass, and the reason why interactions between quarks — the particles that make up protons and neutrons — adhere to a certain symmetry of nature, called CP symmetry, that other types of particle interactions eschew. Now, two researchers say that axions could solve a third thorny problem: why the universe is made mostly of matter, while antimatter is rare. In the early universe, the axion could have behaved in a manner that produces an excess of matter, particle physicists Raymond Co and Keisuke Harigaya suggest in the March 20 Physical Review Letters. “They have an idea which has all the right ingredients to do some interesting things,” says physicist Michael Dine of the University of California, Santa Cruz. But it remains to be seen whether the idea can fully reproduce...