When dealing with particle interactions, is there a straightforward way to work out the charge on the W boson?

In particular, the interactions I need to know the charge for are those involving a proton, neutron, an electron/positron and an electron neutrino/antineutrino. Is it easiest just to remember the charge (for AQA AS Physics exam)?


1 Answer 1


You have to look at the Feynman diagram to know if you can assign a charge.

  • Time-like $W$s carry the same charge as the initial and final states.

  • Space-like $W$s are ambiguous and you can not assign a unique charge to them, because you can't say which vertex came first in time.

For interaction that can occur through either time-like or space-like channels you still have the ambiguity.

  • $\begingroup$ All W bosons have a charge. It is just the type of charge that matters. You could look at the charge of the initial particle and the charge of the end particle to figure out the charge of the W boson. $\endgroup$ May 7, 2020 at 22:09
  • $\begingroup$ For example if a neutron turns into a proton it would release a negatively charged W boson. But if a proton turns into a neutron it must have emitted a positively charged W boson. $\endgroup$ May 7, 2020 at 22:10

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