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You wrote:
What are the products from an encounter between a neutrino and an anti-neutrino?


Dear Mr. Moore:
The question of a neutrino and anti-neutrino encounter is interesting. First of all, the strength of the neutrino interaction is very weak, even neutrino interactions with protons or neutrons are very rare but we do measure them in experiments at Fermilab. The probability of a neutrino - antineutrino interaction is so small that it has never been directly observed. Such interactions to occur as part of the vacuum all the time and in that sense are part of the structure of our everyday world together with all of the other "virtual" particle- antiparticle interactions in the vacuum. But now to try to directly answer your question.

If a neutrino and anti-neutrino did interact the products would be the same as any other particle - antiparticle reaction. Combining a particle with an antiparticle gives no net distinguishing characteristics.

The antiparticle is the opposite of the particle in all of its characteristics so in the reaction, they "cancel out". All that is left is the energy of the particle and the antiparticle. This energy is then converted to all the particles possible both massless particles such as the photon, and massive particles such as electrons, quarks, or Zs just so long as the net characteristics (such as charge or spin) cancel for the products. Massive particles are possible because E=mc**2, energy can be converted into mass. Of course there are a lot of details that I left out but that is the fundamental answer to your question, as far as we know in our current theories (the standard model of particle interactions). Since no one has ever observed a neutrio-antineutrino interaction we could be surprised and need to re-examine our knowledge of the underlying structure of the universe.

I hope that this responds to your question. Please continue your probing into some of nature's most important secrets.

Ken Heller

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last modified 1/25/2001   physicsquestions@fnal.gov