Unanswered Questions

Beyond the Proton, Neutron, and Electron

Beta decay involves neutrons, protons, electrons, and neutrinos. How is it explained using quarks?

Beta decay involves two steps. First the down quark changes to an up quark with the emission of a W- boson. Then, almost instantaneously the W- changes into an electron and anti-neutrino. Physicists diagram the two beta decay processes this way:

When a nucleus undergoes beta decay the number of neutrons goes down by one, the number of protons goes up by one, and an electron and anti-neutrino are emitted. In terms of quarks and leptons one of the down quarks in the neutron is changed to an up quark in the proton, and a lepton (electron) and anti-lepton (anti-neutrino) are emitted. The change from down to up quark is a flavor change and that can occur only in beta decay. When a positron is emitted in inverse beta decay, an up quark in the proton is changed to a down quark in the neutrino and a lepton (neutrino) and anti-lepton (positron) are emitted.


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