Eur. Phys. J. C 19, 441-454
DOI: 10.1007/s100520100610
Finite width effects and gauge cancellations in W- and Z-boson production in the framework of modified perturbation theory
M.L. NekrasovInstitute for High Energy Physics, 142280 Protvino, Russia
(Received: 21 February 2000 / Revised version: 18 October 2000 / Published online: 23 March 2001 -© Springer-Verlag 2001)
Abstract
The processes of production and subsequent decay of W-
and Z-bosons in e+ e- collisions are considered in a recently
proposed modified perturbation theory (PT), based on a direct
expansion of probabilities instead of amplitudes. In such an
approach the non-integrable singularities in the phase space, which
are intrinsic in the conventional PT, appear as singularities in
the coupling constant (with subsequent compensation by the decay
factors of unstable particles). In the present paper the
systematic investigation of the modified PT is carried out. The
results are compared with the results of the conventional
approach, based on the calculation of the amplitude with Dyson
resummation. A solution to the problem of the loss of one-loop PT
order in the resonance region is found. On the basis of this
solution the proof of gauge cancellations in any order of the
modified PT is given. A simple generalization of the fermion-loop
scheme is proposed which provides a complete description of W-pair
production in a next-to-leading order approximation.
© Società Italiana di Fisica, Springer-Verlag 2001
