Measurement of the I=1 /2 Kpi\u80 S -wave amplitude from Dalitz plot analyses of eta_c -->\u86\u92KKbar pi\u80 in two-photon interactions

We study the processes γγ→K0SK±π∓ and γγ→K+K-π0 using a data sample of 519 fb-1 recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e+e- collider at center-of-mass energies at and near the Υ(nS) (n=2, 3, 4) resonances. We observe ηc decays to both final states and perform Dalitz plot analyses using a model-independent partial wave analysis technique. This allows a model-independent measurement of the mass-dependence of the I=1/2 Kpi\u80 S-wave amplitude and phase. A comparison between the present measurement and those from previous experiments indicates similar behavior for the phase up to a mass of 1.5 GeV/c2. In contrast, the amplitudes show very marked differences. The data require the presence of a new a0(1950) resonance with parameters m=1931±14±22 MeV/c2 and Γ=271±22±29 MeV

Observation of B→D(*) π+π−ℓ−νbar Decays in e+e- Collisions at the Υ(4S) Resonance

We report on measurements of the decays of Bbar mesons into the semileptonic final states Bbar-->D(*)pi+pi-l-nubar, where D(*) represents a D or D* meson and l- is an electron or a muon. These measurements are based on 471x10^6 BBbar pairs recorded with the BABAR detector at the SLAC asymmetric B factory PEP-II. We determine the branching fraction ratios R_pi+pi-(*)=B(Bbar-->D(*)pi+pi-l-nubar)/B(Bbar-->D(*)l-nubar) using events in which the second B meson is fully reconstructed. We find Rpi+pi-=0.067±0.010±0.008 and Rpi+pi-=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 Bbar-->D(*)pipil-nubar decays, where pi denotes either a pi± and pi0 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