Effects from multiple QED radiation in Z° and W± leptonic decays

Abstract Decay final states in Z° → l l + + l l − + n γ and W ± → l l ± + ν + n γ are calculaed in the pole (Weizsacker-Williams) approximation. The subasymptotic ambiguities in the latter are fixed so that for single, hard photon emissions it becomes identical to the O(α) approximation. The inclusion of multiphoton decays appears to lead to substantial differences with respect to the O(α) approximation in quantities which sensibly depend on multiple emissions of infrared and collinear photons, like e.g. energy losses undergone by charged leptons. Results are reported, especially focussing on Z° and W ± electron decays. Effects from multiple initial state radiation in electron-positron annihilation are also discussed.