Light meson spectroscopy from Dalitz plot analyses ηc decays to η0K + K − , η0π + π − , and ηπ + π − produced in two-photon interactions

We study the processes γγ → ηc → η0KþK−, η0πþπ−, and ηπþπ− 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. This is the first observation of the decay ηc → η0KþK− and we measure the branching fraction Γðηc → η0KþK−Þ=ðΓðηc → η0πþπ−Þ 1⁄4 0.644 0.039stat 0.032sys. Significant interference is observed between γγ → ηc → ηπþπ− and the nonresonant two-photon process γγ → ηπþπ−. A Dalitz plot analysis is performed of ηc decays to η0KþK−, η0πþπ−, and ηπþπ−. Combined with our previous analysis of ηc → KK ̄ π, we measure the K 0ð1430Þ parameters and the ratio between its η0K and πK couplings. The decay ηc → η0πþπ− is dominated by the f0ð2100Þ resonance, also observed in J=ψ radiative decays. A new a0(1700)→ ηπ resonance is observed in the ηc → ηπþπ− channel. We also compare ηc decays to η and η0 final states in association with scalar mesons as they relate to the identification of the scalar glueball

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