Lees, J. P.Poireau, V.Tisserand, V.Grauges, E.Palano, A.Eigen, G.Stugu, B.Izen, Joseph M.Lou, XinchouBaBar Collaboration2016-09-232016-09-232016-01-262016-01-260031-9007http://hdl.handle.net/10735.1/5048We report on measurements of the decays of B̅ mesons into the semileptonic final states B̅ → D^{(*)} π⁺π⁻ℓ⁻ν̅, where D^{(*())} represents a D or D* meson and ℓ⁻ is an electron or a muon. These measurements are based on 471 x 10⁶ BB̅ pairs recorded with the BABAR detector at the SLAC asymmetric B factory PEP-II. We determine the branching fraction ratios R(π⁺π⁻)* = β(B̅ → D* π⁺π⁻ℓ⁻ν̅ /B (B̅ → D*ℓ⁻ν̅) using events in which the second B meson is fully reconstructed. We find Rπ⁺π⁻ = 0.067 ± 0.010 ± 0.008 and R(π⁺π⁻)* = 0.019 ± 0.005 ± 0.004, where the first uncertainty is statistical and the second is systematic. Based on these results and assuming isospin invariance, we estimate that B̅ → D^{(*)}ππ ℓ⁻ν̅ decays, where π denotes either a π^± and π⁰ meson, account for up to half the difference between the measured inclusive semileptonic branching fraction to charm hadrons and the corresponding sum of previously measured exclusive branching fractions.en©2016 American Physical SocietyB mesonsBranching fractions (Nuclear physics)Monte Carlo methodsLeptonic decaysUpsilon particlesArticleLees, J. P., V. Poireau, V. Tisserand, E. Grauges, et al. 2016. "Observation of B̅ → D^{(*)} π⁺π⁻ℓ⁻ν̅ decays in e⁺e⁻ collisions at the ϒ(4S) resonance." Physical Review Letters 116(4), doi:10.1103/PhysRevLett.116.041801.1164