u.washington.eduIntroduction
"[I]n the 1979 Nobel prize-winning theoretical work of Sheldon Glashow, Abdus Salam, and Steven Weinberg (all working separately) it was shown that the weak and electromagnetic interactions, formerly considered distinct, are in fact merely two aspects of the same "electroweak" interaction... At very high energies, the intrinsic mass of a particle becomes irrelevant, and the behaviors of the mediating particles [W, Z, and photons] converge." [1] The symmetry is broken at some point as the energies drop; in the Standard Model, the bosons acquire mass through interaction with vacuum Higgs fields. [2] The point at which the electroweak symmetry breaking occurs is expected to be "[not] too far above the W and Z masses." [3]
Please note: I do not understand the math behind this. When I do, I'll post it here.