What matters in universe’s asymmetry

SYRACUSE U. (US) — A study of the decay of a rare particle present right after the Big Bang could help solve the mystery of why the universe evolved to have more matter than antimatter.

Using scientific data from experiments on the Large Hadron Collider (LHC) at the CERN laboratory near Geneva, Switzerland, researchers observed the decomposition of a special type of B meson, created when protons traveling at nearly the speed of light smash into each other.

Scientists are eager to study B mesons because of their potential for yielding information about the relationship between matter and antimatter moments after the Big Bang, as well as yet-to-be-described forces that resulted in the rise of matter over antimatter.

“We know when the universe formed from the Big Bang, it had just as much matter as antimatter,” says Sheldon Stone, professor of physics at Syracuse University. “But we live in a world predominantly made of matter, therefore, there had to be differences in the decaying of both matter and antimatter in order to end up with a surplus of matter.”

The work is part of two studies published in the journal Physics Letters B.

All matter is composed of atoms, which are composed of protons (positive charge), electrons (negative charge), and neutrons (neutral). The protons and neutrons are composed, in turn, of even smaller particles called quarks.

Antimatter is composed of antiprotons, positrons (the opposite of electrons), antineutrons and thus anti-quarks. While antimatter generally refers to sub-atomic particles, it can also include larger elements, such as hydrogen or helium.

It is generally believed that the same rules of physics should apply to both matter and antimatter and that both should occur in equal amounts in the universe. That they don’t play by the same rules or occur in equal amounts are among the greatest unsolved problems in physics today.

B mesons are a rare and special subgroup of mesons composed of a quark and anti-quark. While B mesons were common after the Big Bang, they are not believed to occur in nature today and can only be created and
observed under experimental conditions in the LHC or other high-energy colliders.

Because they don’t play by the same rules of physics as most other matter, scientists believe B mesons may have played an important role in the rise of matter over antimatter. The particles may also provide clues about the nature of the forces that led to this lack of symmetry in the universe.

“We want to figure out the nature of the forces that influence the decay of these [B meson] particles,” Stone says. “These forces exist, but we just don’t know what they are. It could help explain why antimatter decays differently than matter.”

Stone’s research is funded by the National Science Foundation.

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