Charged current interactions (as opposed to

neutral current Weak neutral current interactions are one of the ways in which subatomic particles can interact by means of the weak force. These interactions are mediated by the Z boson. The discovery of weak neutral currents was a significant step towa ...

interactions) are one of two primary channels in which subatomic particles can interact by means of the weak force. These interactions are specifically mediated by the and bosons.

Overview

Charged current interactions are the most easily detected class of weak interactions. The weak force is best known for mediating

nuclear decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

. It has very short range, but is the only force (apart from

gravity In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...

) to interact with

neutrinos A neutrino ( ; denoted by the Greek letter ) is an elementary particle that interacts via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small ('' -ino'') that it ...

. The weak force is communicated via the W and Z exchange particles. Of these, the W-boson has either a positive or negative

electric charge Electric charge (symbol ''q'', sometimes ''Q'') is a physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative''. Like charges repel each other and ...

, and mediates neutrino absorption and emission by or with an electrically charged particle. During these processes, the W-boson induces electron or

positron emission Positron emission, beta plus decay, or β+ decay is a subtype of radioactive decay called beta decay, in which a proton inside a radionuclide nucleus is converted into a neutron while releasing a positron and an electron neutrino (). Positron emi ...

or absorption, or changing the flavour of a quark as well as its electrical charge, such as in

beta decay In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which an atomic nucleus emits a beta particle (fast energetic electron or positron), transforming into an isobar of that nuclide. For example, beta decay of a neutron ...

or K-capture. By contrast, the Z particle is electrically neutral, and exchange of a Z-boson leaves the interacting particles' quantum numbers unaffected, except for a transfer of momentum, spin, and energy. Because exchange of W bosons involves a transfer of electric charge (as well as a transfer of

weak isospin In particle physics, weak isospin is a quantum number relating to the electrically charged part of the weak interaction: Particles with half-integer weak isospin can interact with the bosons; particles with zero weak isospin do not. Weak isospin ...

, while

weak hypercharge In the Standard Model (mathematical formulation), Standard Model of electroweak interactions of particle physics, the weak hypercharge is a quantum number relating the electric charge and the third component of weak isospin. It is frequently deno ...

is not transferred), it is known as "charged current". By contrast, exchanges of Z bosons involve no transfer of electrical charge, so it is referred to as a "

". In the latter case, the word "current" has nothing to do with electricity – it simply refers to the Z bosons' movement between other particles.

Definition

The name "charged current" arises due to currents of fermions coupled to the W bosons having electric charge. For example, the charged current contribution to the → elastic scattering amplitude is: :

\mathfrak^ \propto J_^(\mathrm\to\nu_) \; J^(\nu_\to\mathrm),

where the charged currents describing the flow of one

fermion In particle physics, a fermion is a subatomic particle that follows Fermi–Dirac statistics. Fermions have a half-integer spin (spin 1/2, spin , Spin (physics)#Higher spins, spin , etc.) and obey the Pauli exclusion principle. These particles i ...

into the other are given by: :

J^(f\to f') = \bar_\gamma^\frac\left(1-\gamma^\right)u_.

The W-Boson can couple to any particle with

(i.e. any

left-handed In human biology, handedness is an individual's preferential use of one hand, known as the dominant hand, due to and causing it to be stronger, faster or more dextrous. The other hand, comparatively often the weaker, less dextrous or simply l ...

Standard Model The Standard Model of particle physics is the Scientific theory, theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions – excluding gravity) in the unive ...

fermions).The W-Boson can also couple with any

electroweak In particle physics, the electroweak interaction or electroweak force is the unified description of two of the fundamental interactions of nature: electromagnetism (electromagnetic interaction) and the weak interaction. Although these two forc ...

gauge boson In particle physics, a gauge boson is a bosonic elementary particle that acts as the force carrier for elementary fermions. Elementary particles whose interactions are described by a gauge theory interact with each other by the exchange of gauge ...

and the

Higgs Boson The Higgs boson, sometimes called the Higgs particle, is an elementary particle in the Standard Model of particle physics produced by the excited state, quantum excitation of the Higgs field, one of the field (physics), fields in particl ...

, but these are typically not characterized as charged current interactions.

Notes

References

Electroweak theory {{Particle-stub

Overview

Definition

See also

Notes

References