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IHEP 98 - 57
(In Russian) | |
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| M.L. Nekrasov | ||
| Finite width Effects and Gauge Cancellations in W- and Z-Bozon Pproduction in Framework of Modified Perturbation Theory | ||
| Protvino, 1999.-p.24, refs.:26. | ||
The processes of unstable W- and Z-boson production are considered in a recently proposed modified perturbation theory (PT), based on expansion directly of probabilities, instead of amplitudes. In such approach the nonintegrable singularities in a phase space, which are intrinsic in a usual PT, appear as a singularity on a coupling constant (compensated then by the decay factors of unstable states). In the present work the systematic research of the modified PT is carried out and the obtained results are compared to ones of the usual approach based on calculation of amplitude with Dyson resummation. The solution of the problem of reducing one loop-order in a resonance region, causing to paradoxical results in the usual approach, is discovered. On the basis of this solution the proof of gauge cancellations in any order of the modified PT is given. It is shown, that the results obtained in the modified PT may be reproduced within the limits of given accuracy in the usual approach provided that an anomalous term is added to the probability. A simple generalization of the fermion-loop scheme is determined which allows one to fulfil the complete description of W-pair production in NLO approximation.
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