Skip to main content
Physics LibreTexts

6.4: Weak Nuclear Force

  • Page ID
  • \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)

    The weak nuclear force manifests itself through nuclear \(\beta\) decay, \[n\rightarrow p+e^{-}+\overline{\nu}_e.\] The standard coupling for this theory is called the Fermi coupling, \(G_F\), after its discoverer. After the theory was introduced it was discovered that there were physical particles that mediate the weak force, the \(W^{\pm}\) and the \(Z^0\) bosons. These are very heavy particles (their mass is about 80 times the proton mass!), which is why they have such a small range – fluctuations where I need to create that much mass are rare. The \(W^{\pm}\) bosons are charged, and the \(Z^0\) boson is neutral. The typical \(\beta\) decay referred to above is mediated by a \(W^-\) boson as can be seen in the Feynman diagram in Figure \(\PageIndex{1}\). The reason for this choice is that it conserves charge at each point (the charge of a proton and a \(W^-\) is zero, the charge of an electron and a neutrino is -1, the same as that of a \(W^-\)).

    Figure \(\PageIndex{1}\): The Feynman diagram for the weak decay of a neutron.

    This page titled 6.4: Weak Nuclear Force is shared under a CC BY-NC-SA 2.0 license and was authored, remixed, and/or curated by Niels Walet via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.