2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/179150We study the contribution of B_c mesons to the search for B->tau nu decays. We find that at LEP the contributions from B_u and B_c 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->tau nu final states. Inclusion of the B_c contribution can reduce the current L3 limit on Tan(beta)/M_H from 0.38/GeV (90%CL) down to 0.27/GeV (90%CL).8 pages, Latex, epsfig, 1 figureHigh Energy Physics - PhenomenologyHigh Energy Physics - Experimenttext