Bloch-Nordsieck violation in spontaneously broken Abelian theories - art.no. 211802

We point out that, in a spontaneously broken U(1) gauge theory, inclusive p rocesses, whose primary particles are mass eigenstates that do not coincide with the gauge eigenstates, are not free of infrared logarithms. The charg e mixing allowed by symmetry breaking and the ensuing Bloch-Nordsieck viola tion are here analyzed in a few relevant cases and in particular for proces ses initiated by longitudinal gauge bosons. Of particular interest is the e xample of weak hypercharge in the standard model where, in addition, left-r ight mixing effects arise in transversely polarized fermion beams.