|
|
| (One intermediate revision by one other user not shown) |
| Line 1: |
Line 1: |
| {{Flavour_quantum_numbers}}
| | Hello! My name is Augusta. I am pleased that I could unite to the entire globe. I live in Netherlands, in the ZH region. I dream to visit the different nations, to obtain familiarized with fascinating individuals.<br><br>Also visit my web page - [http://theminecraftwiki.com/index/index.php?title=User:FloyEdwards How To Get Free Fifa 15 Coins] |
| | |
| In [[particle physics]], '''weak isospin''' is a [[quantum number]] relating to the [[weak interaction]], and parallels the idea of [[isospin]] under the [[strong interaction]]. Weak isospin is usually given the symbol ''T'' or ''I'' with the third component written as ''T<sub>z</sub>'', ''T<sub>3</sub>'', ''I''<sub>z</sub> or ''I''<sub>3</sub>.<ref>Ambiguities: ''I'' is also used as sign for the 'normal' [[isospin]], same for the third component ''I''<sub>3</sub> aka ''I''<sub>z</sub>. ''T'' is also used as the sign for [[Topness]]. This article uses ''T'' and ''T''<sub>3</sub>.</ref> Weak isospin is a complement of the [[weak hypercharge]], which unifies [[weak interactions]] with [[Electromagnetic force|electromagnetic]] interactions.
| |
| | |
| The '''weak isospin conservation law''' relates the conservation of ''T''<sub>3</sub>; all weak interactions must preserve ''T''<sub>3</sub>. It is also conserved by the other [[fundamental interaction|interactions]] and is therefore a conserved quantity in general. For this reason ''T''<sub>3</sub> is more important than ''T'' and often the term "weak isospin" refers to the "3rd component of weak isospin".
| |
| | |
| ==Relation with chirality==
| |
| [[Fermion]]s with negative [[chirality (physics)|chirality]] (also called left-handed fermions) have ''T'' = {{frac|1|2}} and can be grouped into doublets with ''T''<sub>3</sub> = ±{{frac|1|2}} that behave the same way under the [[weak interaction]]. For example, up-type [[quarks]] ([[up quark|u]], [[charm quark|c]], [[top quark|t]]) have ''T''<sub>3</sub> = +{{frac|1|2}} and always transform into down-type quarks ([[down quark|d]], [[strange quark|s]], [[bottom quark|b]]), which have ''T''<sub>3</sub> = −{{frac|1|2}}, and vice-versa. On the other hand, a quark never decays weakly into a quark of the same ''T''<sub>3</sub>. Something similar happens with left-handed [[lepton]]s, which exist as doublets containing a charged lepton ({{SubatomicParticle|link=yes|Electron-}}, {{SubatomicParticle|link=yes|Muon-}}, {{SubatomicParticle|link=yes|Tau-}}) with ''T''<sub>3</sub> = −{{frac|1|2}} and a [[neutrino]] ({{SubatomicParticle|link=yes|Electron neutrino}}, {{SubatomicParticle|link=yes|Muon neutrino}}, {{SubatomicParticle|link=yes|Tau neutrino}}) with ''T''<sub>3</sub> = {{frac|1|2}}.
| |
| | |
| [[Fermion]]s with positive chirality (also called right-handed fermions) have ''T'' = 0 and form singlets that do not undergo weak interactions.
| |
| | |
| Electric charge, ''Q'', is related to weak isospin, ''T''<sub>3</sub>, and weak hypercharge, ''Y''<sub>W</sub>, by
| |
| :<math> Q = T_3 + \frac{Y_\mathrm{W}}{2}.</math>
| |
| | |
| == Weak isospin and the W bosons ==
| |
| The symmetry associated with spin is [[SU(2)]]. This requires gauge [[boson]]s to transform between weak isospin charges: bosons {{SubatomicParticle|W boson+}}, {{SubatomicParticle|W boson-}} and {{SubatomicParticle|W boson0}}. This implies that {{SubatomicParticle|W boson}} bosons have a ''T'' = 1, with three different values of ''T<sub>3</sub>''.
| |
| | |
| * {{SubatomicParticle|W boson+}} boson (''T<sub>3</sub>'' = +1) is emitted in transitions {(''T<sub>3</sub>'' = +{{frac|1|2}}) → (''T<sub>3</sub>'' = −{{frac|1|2}})},
| |
| * {{SubatomicParticle|W boson-}} boson (''T<sub>3</sub>'' = −1) is emitted in transitions {(''T<sub>3</sub>'' = −{{frac|1|2}}) → (''T<sub>3</sub>'' = +{{frac|1|2}})}.
| |
| * {{SubatomicParticle|W boson0}} boson (''T<sub>3</sub>'' = 0) would be emitted in reactions where ''T<sub>3</sub>'' does not change. However, under [[electroweak]] unification, the {{SubatomicParticle|W boson0}} boson mixes with the [[weak hypercharge]] gauge boson {{SubatomicParticle|B boson}}, resulting in the observed {{SubatomicParticle|Z boson0}} boson and the [[photon]] of [[Quantum Electrodynamics]].
| |
| | |
| == See also ==
| |
| * [[standard model (basic details)|Field theoretical formulation of standard model]]
| |
| * [[Weak hypercharge]]
| |
| | |
| == References ==
| |
| {{Reflist}}
| |
| | |
| [[Category:Theoretical physics]]
| |
| [[Category:Particle physics flavour quantum number]]
| |
| [[Category:Standard Model]]
| |
| [[Category:Electroweak theory]]
| |
Hello! My name is Augusta. I am pleased that I could unite to the entire globe. I live in Netherlands, in the ZH region. I dream to visit the different nations, to obtain familiarized with fascinating individuals.
Also visit my web page - How To Get Free Fifa 15 Coins