23.1. The Big Idea http://www.ck12.org
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In this case, the electron and positron are exchanging virtual electron/positron pairs.12.
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- Draw all of the possible Feynman diagrams for the annihilation of an electron and positron, followed by
motion of an exchange particle, followed by the creation of a new electron and positron. - Draw the Feynman diagram for the collision of an up and anti-down quark followed by the production of a
positron and electron neutrino.
Answers to Selected Problems
- Allowed: an electron and anti-electron(positron) annihilate to a photon then become an electron and anti-
electron(positron) again. - Not allowed: electrons don’t go backward though time, and charge is not conserved
- Not allowed: lepton number is not conserved
- Allowed: two electrons exchange a photon
- Not allowed: neutrinos do not have charge and therefore cannot exchange a photon.
- Allowed: an electron and an up quark exchange a photon
- Not allowed: lepton number not conserved
- Not allowed: quark number not conserved
- Allowed: electron neutrino annihilates with a positron becomes aW+then splits to muon and muon neutrino.
- Allowed: up quark annihilates with anti-up quark becomesZ^0 , then becomes a strange quark and anti-strange
quark - Not allowed: charge not conserved
- Allowed: this is a very rare interaction