- Are the massive gauge bosons of electroweak theory (W, Z) permitted in the external legs of Feynman diagrams?
Because massive gauge bosons have a finite half life, are they excluded from the (infinitely, asymptotically remote?) in and out states of QFT? Or, to put it another way, are they restricted to the internal legs of Feynman diagrams, i.e. to being virtual only? We can see W and Z tracks in bubble or cloud chambers, is this sufficient to guarantee their "real" existence?