2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/97810We have performed a search for the leptonic B decay B+ --> mu+ nu_mu with data collected at the Upsilon(4S) resonance by the BABAR experiment at the PEP-II storage ring. With an integrated luminosity of approximately 81.4 fb-1 (88.4 million BBbar pairs), we find no convincing evidence for a signal and set a preliminary upper limit on the branching fraction of BR(B+ --> mu+ nu_mu) < 6.6 x 10^{-6} at the 90% confidence level.17 pages, 7 postscript figures, submitted to International Europhysics Conference on High-Energy Physics 2003High Energy Physics - Experimenttext