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

Radiative corrections to processes that involve the production and subseque nt decay of unstable particles are complex due to various theoretical and p ractical 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 differ ent stages of the reaction, and overlapping resonances. Within the double-p ole approximation the complete O(alpha) electroweak corrections are evaluat ed for this off-shell W-pair production process. Examples of the effect of these corrections on a number of distributions are presented, These compris e mass and angular distributions as well as the photon-energy spectrum. (C) 1999 Elsevier Science B.V. All rights reserved.