Editing Weak interaction (section)

=== Charged-current interaction ===
{{main|Charged current}}
[[File:Beta Negative Decay.svg|thumb|right|200px|The [[Feynman diagram]] for beta-minus decay of a [[neutron]] ({{math|n {{=}} udd}}) into a [[proton]] ({{math|p {{=}} udu}}), [[electron]] ({{math|e{{sup|−}}}}), and [[neutrino|electron anti-neutrino]] {{math|{{overline|ν}}{{sub|e}}}}, via a charged vector boson ({{math|{{SubatomicParticle|W boson-}}}}). ]]
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|{{math|{{SubatomicParticle|W boson+}}}}&nbsp;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 {{math|ν{{sub|e}}}}, muon {{math|ν{{sub|μ}}}}, or tau {{math|ν{{sub|τ}}}}) is the same as the type of lepton in the interaction, for example:
: <math> \mu^- + \mathrm{W}^+ \to \nu_\mu </math>
Similarly, a down-type [[quark]] ({{math|d}}, {{math|s}}, or {{math|b}}, with a charge of {{sfrac|−| 1 |3}}) can be converted into an up-type quark ({{math|u}}, {{math|c}}, or {{math|t}}, with a charge of {{sfrac|+| 2 |3}}), by emitting a {{SubatomicParticle|W boson-}}&nbsp;boson or by absorbing a {{math|{{SubatomicParticle|W boson+}}}}&nbsp;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 {{math|{{SubatomicParticle|W boson+}}}}&nbsp;boson, or absorb a {{math|{{SubatomicParticle|W boson-}}}}&nbsp;boson, and thereby be converted into a down-type quark, for example:
: <math>\begin{align}
                 \mathrm{d} &\to \mathrm{u} + \mathrm{W}^- \\
  \mathrm{d} + \mathrm{W}^+ &\to \mathrm{u} \\
                 \mathrm{c} &\to \mathrm{s} + \mathrm{W}^+ \\
  \mathrm{c} + \mathrm{W}^- &\to \mathrm{s}
\end{align}</math>

The W&nbsp;boson is unstable so will rapidly decay, with a very short lifetime. For example:
: <math>\begin{align}
  \mathrm{W}^- &\to \mathrm{e}^- + \bar\nu_\mathrm{e} ~ \\
  \mathrm{W}^+ &\to \mathrm{e}^+ + \nu_\mathrm{e} ~
\end{align}</math>

Decay of a W&nbsp;boson to other products can happen, with varying probabilities.<ref name="PDG2">{{cite journal |author1=Nakamura, K. |display-authors=etal |collaboration=[[Particle Data Group]] |year=2010 |title=Gauge and Higgs Bosons |journal=[[Journal of Physics G]] |volume=37 |issue=7A |page=075021 |doi = 10.1088/0954-3899/37/7a/075021 |bibcode = 2010JPhG...37g5021N |url=http://pdg.lbl.gov/2010/tables/rpp2010-sum-gauge-higgs-bosons.pdf}}</ref>

In the so-called [[beta decay]] of a neutron (see picture, above), a down quark within the neutron emits a [[Virtual particle|virtual]] {{math|{{SubatomicParticle|W boson-}}}} 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 {{math|{{SubatomicParticle|W boson-}}}} boson can only carry sufficient energy to produce an electron and an electron-antineutrino – the two lowest-possible masses among its prospective decay products.<ref name=PDG3>
{{cite journal
 |author1=Nakamura, K.
 |display-authors=etal
 |collaboration=[[Particle Data Group]]
 |year=2010
 |title={{math| {{SubatomicParticle|neutron}} }}
 |journal=[[Journal of Physics G]]
 |volume=37  |issue=7A  |page=7
 |doi=10.1088/0954-3899/37/7a/075021
 |bibcode=2010JPhG...37g5021N
 |url=http://pdg.lbl.gov/2010/listings/rpp2010-list-n.pdf
}}
</ref>
At the quark level, the process can be represented as:
: <math> \mathrm{d} \to \mathrm{u} + \mathrm{e}^- + \bar\nu_\mathrm{e} ~</math>