# Neutral current > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Neutral_current > Markdown URL: https://mediated.wiki/source/Neutral_current.md > Source: https://en.wikipedia.org/wiki/Neutral_current > Source revision: 1323680075 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|Weak force particle interaction}} {{About|weak nuclear force interactions|neutral currents in electric power systems|Ground and neutral}} {{Standard model of particle physics|Electroweak interaction}} Weak '''neutral current''' interactions are one of the ways in which [subatomic particle](/source/subatomic_particle)s can interact by means of the [weak force](/source/weak_force). These interactions are mediated by the [Z boson](/source/Z_boson). The discovery of weak neutral currents was a significant step toward the unification of [electromagnetism](/source/electromagnetism) and the weak force into the [electroweak force](/source/electroweak_force), and led to the discovery of the [W and Z bosons](/source/W_and_Z_bosons). == In simple terms == The weak force is best known for its role in nuclear decay. It has very short range but (apart from gravity) is the only force to interact with [neutrino](/source/neutrino)s. Like other subatomic forces, the weak force is mediated via exchange particles. Perhaps the most well known of the exchange particles for the weak force is the [W particle](/source/W_boson) which is involved in [beta decay](/source/beta_decay). W particles have [electric charge](/source/electric_charge) – there are both positive and negative W particles – however the Z boson is also an exchange particle for the weak force but does ''not'' have any electrical charge. Exchange of a Z boson transfers [momentum](/source/momentum), [spin](/source/Spin_(physics)), and [energy](/source/energy), but leaves the interacting particles' quantum numbers unaffected – charge, [flavor](/source/Flavor_(physics)), [baryon number](/source/baryon_number), [lepton number](/source/lepton_number), etc. Because there is no transfer of electrical charge involved, exchange of Z particles is referred to as "neutral" in the phrase "neutral current". However the word "current" here has nothing to do with electricity – it simply refers to the exchange of the Z particle.{{cite web |title=Neutral current |author=Nave, R. |publisher=GSU |url=http://hyperphysics.phy-astr.gsu.edu/hbase/particles/neucur.html}} The Z boson's neutral current interaction is determined by a derived quantum number called ''[weak charge](/source/weak_charge)'', which acts similarly to [weak isospin](/source/weak_isospin) for interactions with the W 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 {{math|{{SubatomicParticle|Electron neutrino}}{{SubatomicParticle|Electron}} }} → {{math|{{SubatomicParticle|Electron neutrino}}{{SubatomicParticle|Electron}} }} elastic [scattering amplitude](/source/scattering_amplitude) is : \mathfrak{M}^\mathsf{NC} ~\propto~ J_\mu^{\mathsf{(NC)}}(\nu_\mathrm{e} ) \; J^{\mathsf{(NC)}\ \mu}(\mathrm{e^{-}})\ , where the neutral currents describing the flow of the [neutrino](/source/neutrino) and of the electron are given by:{{cite web |title=Lecture 11 - Weak Interactions |department=Particle Physics |type=course notes |publisher=[University of Edinburgh](/source/University_of_Edinburgh) |url=https://www2.ph.ed.ac.uk/~playfer/PPlect11.pdf |access-date=May 20, 2021 |page=7}} : J^{ \mathsf{(NC)}\ \mu }(f) = \bar{u}_{f}\ \gamma^\mu\ \frac{1}{2} \left( g^{f}_\mathsf{V} - g^{f}_\mathsf{A}\ \gamma^{5} \right)\ u_{f}\ , where: : g^{f}_\mathsf{V} = T_3(f) - 2\sin^2\theta_\mathsf{W}\ Q(f) = \frac{1}{2}\ Q_\mathsf{W}(f) and \ g^{f}_\mathsf{A} = T_3(f)\ are the [vector and axial couplings](/source/Chirality_(physics)) for [fermion](/source/fermion) \ f ~. \ T_3\ denotes the [weak isospin](/source/weak_isospin) of the fermions, {{mvar|Q}} their electric charge and \ Q_\mathsf{W}\ their [weak charge](/source/weak_charge). These [couplings amount to essentially left chiral for neutrinos and axial for charged leptons](/source/W_and_Z_bosons). The Z boson can couple to any [Standard Model](/source/Standard_Model) particle, except [gluon](/source/gluon)s and [photon](/source/photon)s ([sterile neutrinos](/source/sterile_neutrinos) would also be an exception, if they were found to exist). 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](/source/photon). Unless the interacting particles have energies on the order of the Z boson mass (91 GeV) or higher, the virtual Z boson exchange has an effect of a tiny correction, \ (E/M_\mathrm{Z})^2\ , to the amplitude of the electromagnetic process. [Particle accelerators](/source/Particle_accelerator) with energies necessary to observe neutral current interactions and to measure the mass of Z boson weren't available until 1983. On the other hand, Z boson interactions involving [neutrino](/source/neutrino)s have distinctive signatures: They provide the only known mechanism for [elastic scattering](/source/elastic_scattering) of neutrinos in matter. Neutrinos are almost as likely to scatter elastically (via Z boson exchange) as inelastically (via [W boson](/source/W_boson) exchange); this effect has considerable significance for neutrino observational experiments, e.g. in the [Sudbury Neutrino Observatory](/source/Sudbury_Neutrino_Observatory) experiment. Weak neutral currents were predicted by [electroweak theory](/source/electroweak_theory) developed mainly by [Abdus Salam](/source/Abdus_Salam), [John Clive Ward](/source/John_Clive_Ward), [Sheldon Glashow](/source/Sheldon_Glashow) and [Steven Weinberg](/source/Steven_Weinberg),{{cite web |title=The Nobel Prize in Physics 1979 |publisher=[Nobel Foundation](/source/Nobel_Foundation) |url=http://www.nobel.se/physics/laureates/1979 |via=nobel.se |access-date=2008-09-10 }} and confirmed shortly thereafter in 1973, in a neutrino experiment in the [Gargamelle](/source/Gargamelle) [bubble chamber](/source/bubble_chamber) at [CERN](/source/CERN). == See also == * [Charged current](/source/Charged_current) * [Flavor changing neutral current](/source/Flavor_changing_neutral_current) * [Neutral particle oscillation](/source/Neutral_particle_oscillation) * [Electric current](/source/Electric_current) * [Quantum chromodynamics](/source/Quantum_chromodynamics) * [Sudbury Neutrino Observatory#Neutral current interaction](/source/Sudbury_Neutrino_Observatory) * [Weak charge](/source/Weak_charge) == References == {{Reflist}} == External links == * {{cite web |url=http://cerncourier.com/cws/article/cern/29168 |title=Discovery of weak neutral currents |website=CERN Courier |date=3 October 2004 |access-date=10 March 2009 |archive-date=20 May 2011 |archive-url=https://web.archive.org/web/20110520115858/http://cerncourier.com/cws/article/cern/29168 |url-status=dead }} * {{cite web |url=http://public.web.cern.ch/public/en/Research/Gargamelle-en.html |title=Gargamelle |series=Research |website=CERN public web |url-status=dead |access-date=2011-08-27 |archive-url=https://web.archive.org/web/20110827031552/http://public.web.cern.ch/public/en/Research/Gargamelle-en.html |archive-date=2011-08-27 }} * {{cite encyclopedia |url=http://www.britannica.com/EBchecked/topic/410842/neutral-current-interaction |encyclopedia=Britannica |article=Neutral current interaction}} * {{cite web |url=http://hyperphysics.phy-astr.gsu.edu/hbase/particles/neucur.html |title=Neutral current |author=Nave, R |publisher=GSU}} * {{cite journal |title=Charged and neutral current neutrino induced nucleon emission reactions |author1=Nieves, J. |author2=Valverde, M. |author3=Vicente Vacas, M.J. |year=2006 |journal=Acta Physica Polonica B |volume=37 |issue=8 |pages=2295–2301 |arxiv=hep-ph/0605221 |bibcode=2006AcPPB..37.2295N |url=http://www.actaphys.uj.edu.pl/vol37/pdf/v37p2295.pdf |archive-url=https://web.archive.org/web/20120121101618/http://www.actaphys.uj.edu.pl/vol37/pdf/v37p2295.pdf |archive-date=2012-01-21 |df=dmy-all}} * {{cite magazine |url=https://www.symmetrymagazine.org/breaking/2009/07/07/gargamelle/ |title=Gargamelle |magazine=Symmetry Magazine |date=2009-07-07}} * {{cite web |url=http://cerncourier.com/cws/article/cern/27904 |title=Twenty-five years of neutral currents |date=3 November 1998 |id=27904 |author=Fraser, Gordon |website=CERN Courier |quote=Gordon Fraser looks back at how confirmation of the existence of neutral currents ushered in a new understanding of physics. |access-date=27 August 2011 |archive-date=13 November 2011 |archive-url=https://web.archive.org/web/20111113004952/http://cerncourier.com/cws/article/cern/27904 |url-status=dead }} *{{Cite web |date=3 July 2023|title=CERN’s neutrino odyssey |url=https://cerncourier.com/a/cerns-neutrino-odyssey/|author=Fenkart, Sanje |website=CERN Courier|quote=Sanje Fenkart reounts the discovery of neutral currents in its 50 years anniversary}} * {{cite web |last=Padilla |first=Antonio (Tony) |title=Gargamelle and neutral currents |url=http://www.sixtysymbols.com/videos/neutral_currents.htm |website=Sixty Symbols |publisher=[University of Nottingham](/source/University_of_Nottingham) |editor=Brady Haran |editor-link=Brady Haran }} {{DEFAULTSORT:Neutral Current}} Category:Electroweak theory --- Adapted from the Wikipedia article [Neutral current](https://en.wikipedia.org/wiki/Neutral_current) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Neutral_current?action=history)). 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