M. Nowakowski et A. Pilaftsis, ON GAUGE-INVARIANCE OF BREIT-WIGNER PROPAGATORS, Zeitschrift fur Physik. C, Particles and fields, 60(1), 1993, pp. 121-125
We present an approach to bosonic (Z0, W+/-) as well as fermionic (top
-quark) Breit-Wigner propagators which is consistent with gauge invari
ance arguments. In particular, for the Z0-boson propagator we extend p
revious analyses and show that the part proportional to k(mu)k(nu)/M2
must be modified near the resonance. We derive a mass shift which agre
es with results obtained elsewhere by different methods. The modified
form of a resonant heavy fermion propagator is also given.