= Neutral-current vector and axial couplings
{title2=$c_V=(g_L+g_R)/2,\quad c_A=(g_L-g_R)/2$}
If a neutral-current vertex has prefactor $g/\cos\theta_W$ and chiral coefficients $g_L,g_R$, then $g_LP_L+g_RP_R=c_V-c_A\gamma^5$, with $c_V=(g_L+g_R)/2$ and $c_A=(g_L-g_R)/2$. For one <Standard Model> charged <lepton>, $(c_V,c_A)=(-1/4+\sin^2\theta_W,-1/4)$; for an active <neutrino>, $(c_V,c_A)=(1/4,1/4)$. A prefactor $g/(2\cos\theta_W)$ instead requires doubled coefficients. Mixing these conventions creates a factor-of-four error in squared amplitudes.
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