New observables for testing Bell inequalities in W boson pair production

We show that testing Bell inequalities in W ± pair systems by measuring their angular correlation suffers from the ambiguity in kinetical reconstruction of the dilepton decay mode. We further propose a new set of Bell observables based on the measurement of the linear polarization of the W bosons that can be used in the semileptonic decay mode of W ± pair, and we analyze the prospects of testing the violation of Bell inequalities at e + e − colliders.