Decay: Different Interactions

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Both strong and weak interactions cause particle decays. Before explaining some differences between these interactions, it is necessary to redefine a few key terms.

Electromagnetic Charge:
Particles with electromagnetic charge attract particles with opposite electric charge, and repel particles with similar charges. The electromagnetic interaction has been unified with the weak interaction into the Electroweak interaction.
Color Charge:
Just as some particles can be electromagnetically charged, other particles have a different kind of charge called color charge. The strong interaction causes the attraction between color charged particles.
Flavor:
A particle's type is referred to as its "flavor." If a particle decays from one type to another it "changes flavor." When a down quark decays into an up quark it would be incorrect to say that the down quark suddenly ceased to be; instead, the down quark changed flavor.

The force carrier for the strong interaction is the electrically neutral, color-charged gluon. The force carriers for the weak interaction are the W+ (electrically positive), W- (electrically negative), and the Z (no electric charge). None of the weak force-carrier particles are color charged.


Typically, the weak force-carrier particles (W±) mediate decays in which particles change electric charge. This usually happens whenever a particle changes flavor. The strong force-carrier particle (the gluon) mediates decays involving a color change. Strong interactions, being stronger, happen faster than weak interactions.


Next Back Look at more information and pictures which use the example of neutron beta decay to explain the weak interaction.