# Proving that the weak hypercharge gauge field is not A

Under the electroweak gauge group $SU(2)_LU(1)_Y$ one identifies the 4 gauge fields $W^+, W^-, W^0, B$. After symmetry breaking $W^0$ and $B$ mix to give the observed fields $Z^0$ and $A$. Is there an intuitive argument showing immediatly that $A$ can not be identified with $B$?

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