Are electroweak particles stable? Photons that [are associated with] the electromagnetic force are stable; while the W and Z bosons that [are associated with] the weak force are short lived. I guess that the high temperate electroweak particles that combine the electromagnetic force and the weak force are stable like the photons; while the W and Z bosons with short lives appear only when needed for decay. Is anybody here familiar enough with the research of the electroweak particles to know if they are stable or not?
 A: The electroweak particles are bosons of weak isospin and weak hypercharge. They can exist when the Higgs field vacuum expectation value is zero. They are massless and are stable. Our well known photons, W and Z particles are actually mixtures of these electroweak particles.
See also this question.
A: It's isn't terribly meaningful to say that Photons made of the electromagnetic force or that the W and Z bosons made of the weak force, though it's certainly true that these particles are the gauge bosons associated with these forces. However the main reason the photon is stable is because it is massless.
An isolated massless particle cannot decay into massive particles because that cannot conserve both energy and momentum simultaneously. And a massless particle cannot decay into massless particles, except in special circumstances, because the proper time of a massless particle is always zero. The exception is where the decay products interact with each other, so for example it is possible for a (massless) gluon to decay into two (massless) gluons. However this may apply only to systems exhibiting confinement - I confess I am unsure about this.
Above the electroweak transition neither photons nor the $W^\pm$ and $Z$ particles exist. Instead we get three gauge bosons, the $W_1$, $W_2$ and $W_3$ particles, associated with the $SU(2)$ symmetry and one gauge boson, the $B$ particle, associated with the $U(1)$ symmetry. All four particles are massless and are therefore stable like the photon.
