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Q & A: Matter and antimatter

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Most recent answer: 10/22/2007
Q:
Is it possible that antimatter and matter exist together. Could the high energy collisions just be breaking the bonds that hold matter and antimatter together. Then when the antimatter comes in contact with other matter anti-matter pairs it causes an imbalance and boom. Would that explain the imbalance of matter antimatter in the universe?
- Bill (age 27)
Clark State, Enon, Ohio
A:
To answer your first question -- yes, matter and antimatter can exist together, if only briefly. There is a trivial case of photons -- they are their own antiparticles (that's kinda cheating, I know). Also, antineutrinos zip around just as much as neutrinos and don't annihilate (at least not too often) because the interaction probability is so darn low. Other matter-antimatter combinations can last for some short amounts of time -- an electron and a positron can orbit each other in a state that resembles a hydrogen atom state, called "positronium". It doesn't last too long, though; the electron and positron annihilate to photons.

Quarks and antiquarks can also coexist within bound states. Pions are particles made up of a quark and an antiquark stuck toghether with the strong nuclear force. They too decay by annihilation when the quarks are antiparticles of each other, and by the weak interaction if the quarks are matter and antimatter but have different charges and cannot annihilate to photons.

I don't see where the imbalance comes from in your scenario. In particular, we need to explain why only one kind of matter (and not antimatter) is dominant in the universe, when we know that if the universe was very, very hot at one time, then there were exactly or at least approximately equal amounts of each kind. It is known now that matter and antimatter don't behave exactly the same way (look under "CP Violation" on the web for more info); we are still studying this kind of effect and still don't have all the answers to why there is so much more matter than antimatter in the universe.

Tom

(published on 10/22/2007)

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