= Tau
{disambiguate=particle}
{title2=$\tau$}
{wiki}
= Tau lepton
{synonym}
The tau is the charged <lepton> of the third <fermion generation>. In the massless approximation its charged-current <W boson> partial <decay width> equals those of the <electron> and <muon>, reflecting lepton universality.
The <tau lepton> has <electric charge> $-1$ in units of the positive elementary <electric charge>; $\tau^+$ is its <antiparticle>. Its <weak charged current> decays make the <tau lepton> useful for testing <lepton universality>. They also illustrate how <particle detection> can establish a short-lived parent through visible daughters and a consistent invisible recoil.
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