The contribution of Bc mesons to the search for B+ → τ+ ντ decays at LEP O

We study the contribution of Bc mesons to the search for B → τντ decays. We find that at LEP the contributions from Bu and Bc mesons can be comparable. This observation can have a relevant impact on the extraction of constraints on new physics (such as charged-Higgs contributions) from current LEP limits on B → τν final states. Inclusion of the Bc contribution can reduce the current L3 limit on tan βMH from 0.38 GeV−1 (90% CL) down to 0.27 GeV−1 (90% CL).