Observation of B0 Meson decays to a1(1260) pi

Abstract

We present preliminary measurements of the B meson decay B0 -> a1(1260)+ pi-, with a1(1260)+ --> pi+ pi+ pi-. The data were recorded with the BABAR detector at PEP II and correspond to 218 million BBbar pairs produced in e+e- annihilation through the Upsilon(4S) resonance. We find the branching fractions B(B0 -> a1(1260)+ pi-) = (40.2 +/- 3.9 +/- 3.9) x 10^-6. The fitted values of the a1(1260) parameters are m_a1 = 1.22 +/- 0.02 GeV/c^2 and Gamma_a1= 423 +/- 50 MeV/c^2

14 pages,4 postscript figures, submitted to XXII International Symposium on Lepton and Photon Interactions at High Energies, 6/30 -- 7/5/2005, Uppsala, Sweden