Chargedcurrent

Charged-current interactions are a class of weak interactions in the Standard Model in which the exchange of charged W bosons changes the electric charge and flavor of participating fermions. They are mediated by W+ and W− bosons and are described by a V−A (vector minus axial vector) coupling between fermions and the W field. In low-energy processes, the strength is conveniently expressed through the Fermi constant G_F, while at higher energies the full electroweak theory with W propagation is required.

In leptonic processes, charged-current interactions convert neutrinos into their corresponding charged leptons and vice versa. A typical charged-current scattering is neutrino-nucleon or neutrino-nucleus interactions that produce a charged lepton in the final state: ν_l + N → l− + X. Charged-current decays also play a central role in leptonic decays such as muon decay, μ− → e− + anti-ν_e + ν_μ, which proceed via W exchange.

In the quark sector, charged-current interactions change quark flavor according to the Cabibbo–Kobayashi–Maskawa (CKM) matrix. This enables processes such as beta decay (d → u) and various meson decays. A canonical example is neutron beta decay: n → p + e− + anti-ν_e. The quark-flavor changing nature of charged currents underpins much of nuclear and particle phenomenology.

Experimentally, charged-current events are distinguished by the presence of a final-state charged lepton corresponding to the interacting neutrino flavor (or vice versa). The cross sections rise with energy in many regimes, and CC processes are a key tool in neutrino detectors, accelerator experiments, and tests of the weak interaction. They are contrasted with neutral-current interactions, which proceed via Z bosons and do not produce a charged lepton.