Exploding Sudakov form factors

Contrary to what naively expected, we find that in spontaneously broken gauge theories the resummations of Sudakov double logs (in the presence of an energy scale Q much larger than the mass scale v of the spontaneous gauge breaking) are exponentiated also with a positive coefficient e+α log2 Q2v2. The amplitudes affected by such a term are proportional to v and have a non-zero total gauge charge. As a working example we consider a model with two Abelian gauge groups U'(1)⊗U(1) with large mass splitting MZ' >>� �MZ, and we compute leading radiative corrections to the decay of the heavy extra Z' boson into light fermions.