Electroweak Interactions
The term "electroweak interaction" describes the modern theory of two interactions: electromagnetic and weak.
In the mid-1800s, Maxwell's work unified two apparently quite different types of phenomena, electricity and magnetism, into a single theory of electromagnetism. Nearly 100 years later, the developers of electroweak theory made another giant conceptual leap, unifying Maxwell's electromagnetism (or rather its quantum field theory descendant, quantum electrodynamics or QED) with the theory of the weak interactions.
The electroweak theory was developed in the period from 1961-1967, primarily by the work of Sheldon Glashow, Steven Weinberg, and Abdus Salam, who were awarded the Nobel Prize in 1979 for this work.
W and Z Bosons
The electroweak theory introduces particles that act as mediators of weak interactions in the same way that photons mediate electromagnetic interactions. These particles, the W and Z bosons, again like the photon, carry one unit of spin. In the electroweak theory, these four particles (photons, W¯, W+, and Z°) are closely related. The strength of the interaction of the W and Z bosons is comparable to that of the photon.
| Unified ElectoWeak | Mass (GeV/c2) |
Electric Charge (e) |
|
|---|---|---|---|
 |
photon | 0 | 0 |
| W¯ | W boson | 80 | +1 |
| W+ | W minus boson | 80 | -1 |
| Z° | Z boson | 91 | 0 |
However, unlike the photon, the W and Z bosons are massive. This causes the beta decay weak interactions to occur at rates much lower than electromagnetic decays (which produce photons) with comparable energy release. The mass of the exchanged particle also leads to an interaction probability that falls off much more rapidly with distance than in the electromagnetic case.
