= Electroweak doublet with negative hypercharge
{title2=$\phi_0=(v,0)^T/\sqrt2,\quad Y=-I/2$}
An electroweak doublet with $Y=-1/2$ has component charges $(0,-1)$ under $Q=T^3+Y$. Its upper-component vacuum therefore preserves <electromagnetism>. The canonical covariant-derivative term gives $m_W=g_2v/2$, $m_Z=v\sqrt{g_1^2+g_2^2}/2$ and a massless <photon>. Neutral <eigenvectors> are proportional to $(g_2,-g_1)$ for $Z$ and $(g_1,g_2)$ for the <photon>. This is the conjugate-doublet convention to the usual positive-hypercharge Higgs doublet and gives the same <mass> ratio and electric coupling.
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