section_path: Interaction types/Charged-current interaction
section_name: Charged-current interaction
paragraph_text: Charged-current interaction
  
  In one type of charged current interaction, a charged lepton (such as an electron or a muon, having a charge of −1) can absorb a W boson (a particle with a charge of +1) and be thereby converted into a corresponding neutrino (with a charge of 0), where the type ("flavour") of neutrino (electron ν, muon ν, or tau ν) is the same as the type of lepton in the interaction, for example:
  
  Similarly, a down-type quark (d, s, or b, with a charge of − + 1 / 3) can be converted into an up-type quark (u, c, or t, with a charge of + + 2 / 3), by emitting a W boson or by absorbing a W boson. More precisely, the down-type quark becomes a quantum superposition of up-type quarks: that is to say, it has a possibility of becoming any one of the three up-type quarks, with the probabilities given in the CKM matrix tables. Conversely, an up-type quark can emit a W boson, or absorb a W boson, and thereby be converted into a down-type quark, for example:
  
  The W boson is unstable so will rapidly decay, with a very short lifetime. For example:
  
  Decay of a W boson to other products can happen, with varying probabilities.
  
  In the so-called beta decay of a neutron (see picture, above), a down quark within the neutron emits a virtual W boson and is thereby converted into an up quark, converting the neutron into a proton. Because of the limited energy involved in the process (i.e., the mass difference between the down quark and the up quark), the virtual W boson can only carry sufficient energy to produce an electron and an electron-antineutrino – the two lowest-possible masses among its prospective decay products. At the quark level, the process can be represented as: