Relation With Chirality
Fermions with negative chirality (also called left-handed fermions) have T = 1⁄2 and can be grouped into doublets with T3 = ±1⁄2 that behave the same way under the weak interaction. For example, up-type quarks (u, c, t) have T3 = +1⁄2 and always transform into down-type quarks (d, s, b), which have T3 = −1⁄2, and vice-versa. On the other hand, a quark never decays weakly into a quark of the same T3. Something similar happens with left-handed leptons, which exist as doublets containing a charged lepton (e−, μ−, τ−) with T3 = −1⁄2 and a neutrino (ν
e, ν
μ, ν
τ) with T3 = 1⁄2.
Fermions 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, T3, and weak hypercharge, YW, by
Read more about this topic: Weak Isospin
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