Bose-Einstein effects and W mass determinations

In e+ef- → W+Wf- → q1q2q3q4 events at LEP 2, the two W decay vertices are much closer to each other than typical hadronization distances. Therefore the Bose-Einstein effects, associated with the production of identical bosons (mainly pions), may provide a ‘cross-talk’ between the W+ and the Wf- decay products. If so, the observable W masses are likely to be affected. We develop algorithms for the inclusion of Bose-Einstein effects in multi-hadronic events. In this way we can study potential uncertainties in the W mass determination. In some scenarios the effects are significant, so that this source of uncertainty cannot be neglected.