Radiative corrections to pair production of unstable particles:: Results for E+E- → 4 fermions

Radiative corrections to processes that involve the production and subsequent decay of unstable particles are complex due to various theoretical and practical problems. The so-called double-pole approximation offers a way out of these problems. This method is applied to the reaction e(+)e(-) --> W+W- --> 4 fermions, which allows us to address all the key issues of dealing with unstable particles, like gauge invariance, interactions between different stages of the reaction, and overlapping resonances. Within the double-pole approximation the complete O(alpha) electroweak corrections are evaluated for this off-shell W-pair production process. Examples of the effect of these corrections on a number of distributions are presented, These comprise mass and angular distributions as well as the photon-energy spectrum. (C) 1999 Elsevier Science B.V. All rights reserved.