Measurement Of The B0 To Pi L Nu And B To Pi0 L Nu Branching Fractions And Determination Of PDF Download

The authors report preliminary measurements of the charmless exclusive semileptonic branching fractions of the B° → ?−l+? and B+ → ?°l+? decays, based on 211 fb−1 of data collected at the ?(4S) resonance by the BABAR detector. In events in which the decay of one B meson to a hadronic final state is fully reconstructed, the semileptonic decay of the second B meson is identified by the detection of a charged lepton and a pion. They measure the partial branching fractions for B° → ?−l+? and B+ → ?°l+? in three regions of the invariant mass squared of the lepton pair, and they obtain the total branching fractions ?(B° → ?−l+?) = (1.14 ± 0.27{sub stat} ± 0.17{sub syst}) x 10−4 and ?(B+ → ?°l+?) = (0.86 ± 0.22{sub stat} ± 0.11{sub syst}) x 10−4. Using isospin symmetry, they measure the combined total branching fraction ?(B° → ?−l+?) = (1.28 ± 0.23{sub stat} ± 0.16{sub syst}) x 10−4. Theoretical predictions of the form-factor are used to determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element.