Weak interaction: Difference between revisions

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In [[particle physics]], the '''weak interaction''', the '''weak force''' or '''weak nuclear force''', is one of the four known [[fundamental interaction]]s of nature, alongside the [[strong interaction]], [[electromagnetism]], and [[gravitation]]. The weak interaction is responsible for the [[radioactive decay]], which plays an essential role in [[nuclear fission]]. The theory of the weak interaction is sometimes called '''quantum flavordynamics''' ('''QFD'''), in analogy with the terms [[Quantum chromodynamics|QCD]] and [[Quantum electrodynamics|QED]], but the term is rarely used because the weak force is best understood in terms of [[Electroweak interaction|electro-weak theory]] (EWT).<ref name="griffiths">{{cite book|last=Griffiths|first=David|title=Introduction to Elementary Particles |year=2009|isbn=978-3-527-40601-2|pages=59–60}}</ref>

In the [[Standard Model]] of [[particle physics]], the weak interaction is caused by the emission or absorption of the force carriers, the [[W and Z bosons]]. All known [[fermion]]s interact through the weak interaction. Fermions are particles that have [[half-integer]] [[spin (physics)|spin]]. Spin is one of the fundamental properties of particles. A fermion can be an [[elementary particle]], such as the [[electron]], or it can be a [[composite particle]], such as the [[proton]]. The masses of W⁺, W^&minus;, and Z bosons are each far greater than that of interacting protons or neutrons, which is consistent with the short range of the weak force. The force is termed ''weak'' because its [[field strength]] over a given distance is typically several orders of magnitude less than that of the [[strong interaction|strong nuclear force]] and [[electromagnetism|electromagnetic force]].