= Cabibbo angle
{c}
{title2=$\theta_C$}
The <Cabibbo angle> $\theta_C$ describes the real two-generation <quark mixing> rotation
$$
V=\begin{pmatrix}\cos\theta_C&\sin\theta_C\\-\sin\theta_C&\cos\theta_C\end{pmatrix}.
$$
Thus $V_{ud}=V_{cs}=\cos\theta_C$, $V_{us}=\sin\theta_C$ and $V_{cd}=-\sin\theta_C$. <Nicola Cabibbo> formulated the mixing of <weak charged current> couplings before the three-generation mechanism of <CP violation>; this foundational contribution is distinct from the later extension.<Nicola Cabibbo (1935-2010) by CERN>[description, original weak-current formulation and later three-family extension]{ref}
Back to article page
