Balanced prime

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 Template:SubatomicParticle boson. 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.

Definition

The neutral current that gives the interaction its name is that of the interacting particles. For example, the neutral-current contribution to the Template:SubatomicParticleTemplate:SubatomicParticle → Template:SubatomicParticleTemplate:SubatomicParticle elastic scattering amplitude

${\mathfrak{M}}^{\mathrm{N}\mathrm{C}}\propto J_{\mu }^{\mathrm{(}\mathrm{N}\mathrm{C}\mathrm{)}}({\nu }_{\mathrm{e}})J^{\mathrm{(}\mathrm{N}\mathrm{C}\mathrm{)}\mu }({\mathrm{e}}^{\mathrm{-}})$

where the neutral currents describing the flow of the neutrino and of the electron are given by

$J^{\mathrm{(}\mathrm{N}\mathrm{C}\mathrm{)}\mu }(f)={\overline{u}}_f{\gamma }^{\mu }\frac{1}{2}(g_V^f-g_A^f{\gamma }^5)u_f,$

and $g_V^f$ and $g_A^f$ are the vector and axial vector couplings for fermion $f$.

The Template:SubatomicParticle boson can couple to any Standard Model particle, except gluons and photons. However, any interaction between two charged particles that can occur via the exchange of a virtual Template:SubatomicParticle boson can also occur via the exchange of a virtual photon. Unless the interacting particles have energies on the order of the Template:SubatomicParticle boson mass (91 GeV) or higher, the virtual Template:SubatomicParticle boson exchange has an effect of a tiny correction ( $(E/M_Z{)}^2$ ) to the amplitude of the electromagnetic process. Particle accelerators with energies necessary to observe neutral current interactions and to measure the mass of Template:SubatomicParticle boson weren't available until 1983.

On the other hand, Template:SubatomicParticle 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 Template:SubatomicParticle boson exchange) as inelastically (via Template:SubatomicParticle boson exchange). Weak neutral currents were predicted in 1973 by Abdus Salam, Sheldon Glashow and Steven Weinberg, and confirmed shortly thereafter in 1974, in a neutrino experiment in the Gargamelle bubble chamber at CERN.

See also

• Charged current
• Flavor changing neutral current
• Quantum chromodynamics

References

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External links

• THE DISCOVERY OF WEAK NEUTRAL CURRENTS, CERN Courier
• public web CERN
• britannica
• R Nave
• http://www.actaphys.uj.edu.pl/vol37/pdf/v37p2295.pdf
• http://www.symmetrymagazine.org/breaking/2009/07/07/gargamelle/
• cerncourier
• Template:Cite web