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Neutral current
From Wikipedia, the free encyclopedia
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 Z0 boson, and the interaction is called 'neutral' because the Z0 has no electric charge. The discovery of weak neutral currents was a significant step toward the unification of electromagnetism and the weak force into the electroweak force, and led to the discovery of the W and Z bosons.
Z boson can couple to any Standard Model particle, except gluon. However, any interaction between two charged particles that can occur via the exchange of a virtual Z boson can also occur via the exchange of a virtual photon. Unless interacting particles have energies on the order of the Z boson mass (91 GeV) or higher, virtual Z boson exchange has an effect of a tiny correction ( 
) to the amplitude of electromagnetic process. Particle accelerators with energies necessary to observe neutral current interactions and to measure the mass of Z boson weren't available till 1983.
On the other hand, Z boson interactions involving neutrinos have distinctive signatures: They provide the only known mechanism for elastic scattering of neutrinos in matter; neutrinos are almost as likely to scatter elastically (via Z boson exchange) as inelastically (via W boson exchange). Weak neutral currents were predicted in 1973 and confirmed shortly thereafter, in 1974 in a neutrino experiment in the Gargamelle bubble chamber at CERN.
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