none495siWe have performed a search for the rare leptonic decays B+→+ν(l=e,μ), using data collected at the Υ(4S) resonance by the BABAR detector at the PEP-II storage ring. In a sample of 468×106 BB̄ pairs we find no evidence for a signal and set an upper limit on the branching fractions B(B+→μ+νμ)<1.0×10-6 and B(B+→e+νe)<1.9×10-6 at the 90% confidence level, using a Bayesian approach. © 2009 The American Physical Society.noneAubert, B; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Prencipe, E.; Prudent, X.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M.; Palano, A.; Pappagallo, M.; Eigen, G.; Stugu, B.; Sun, L.; Battaglia, M.; Brown, D.N.; Kerth, L.T.; Kolomensky, Yu.G.; Lynch, G.; Osipenkov, I.L.; Tackmann, K.; Tanabe, T.; Hawkes, ...