See page 39:
http://www.staff.science.uu.nl/~hooft101/lectures/basisqft.pdf
"Representing the Higgs scalar in terms of four real field components,
the Brout-Englert Higgs mechanism is found to remove three of them,
leaving only one neutral, physical
Higgs particle. SU(2) × U(1) is broken into a diagonal subgroup U(1).
Three of the four
gauge fields gain a mass. The one surviving photon field is obtained
after re-diagonalizing
the vector fields; it is a linear composition of the original U(1) field
and one of the three
components of the SU(2) gauge fields."
Saibal