Study of Y(3S,2S) → ηY(1S) and Y(3S,2S) → π^+π^-Y(1S) hadronic transitions

We study the Υ(3S,2S)→ηΥ(1S) and Υ(3S,2S)→π^+π^-Υ(1S) transitions with 122×10^6Υ(3S) and 100×10^6Υ(2S) mesons collected by the BABAR detector at the PEP-II asymmetric-energy e^+e^- collider. We measure B[Υ(2S)→ηΥ(1S)]=(2.39±0.31(stat.)±0.14(syst.))×10^(-4) and Γ[Υ(2S)→ηΥ(1S)]/Γ[Υ(2S)→π^+π^-Υ(1S)]=(1.35±0.17(stat.)±0.08(syst.))×10^(-3). We find no evidence for Υ(3S)→ηΥ(1S) and obtain B[Υ(3S)→ηΥ(1S)]<1.0×10^(-4) and Γ[Υ(3S)→ηΥ(1S)]/ Γ[Υ(3S)→π^+π^-Υ(1S)]<2.3×10^(-3) as upper limits at the 90% confidence level. We also provide improved measurements of the Υ(2S)-Υ(1S) and Υ(3S)-Υ(1S) mass differences, 562.170±0.007(stat.)±0.088(syst.)  MeV/c^2 and 893.813±0.015(stat.)±0.107(syst.)  MeV/c^2, respectively

Branching fraction measurements of the color-suppressed decays B̅^0 to D^((*)0_π^(0), D^((*)0)η, D^((*)0)ω, and D^((*)0)η′ and measurement of the polarization in the decay B̅ 0→D^(*0)ω

We report updated branching fraction measurements of the color-suppressed decays B̅ ^(0) → D^(0)π^(0), D^(*0)π^(0), D^(0)η, D^(*0)η, D^(0)ω, D^(*0)ω, D^(0)η′, and D^(*0)η′. We measure the branching fractions (×10^(-4)): B(B̅^0 → D^(0)π^(0)) = 2.69±0.09±0.13, B(B̅^(0) → D^(*0)π^(0)) = 3.05±0.14±0.28, B(B̅^(0) → D^(0)η) = 2.53±0.09±0.11, B(B̅^(0) → D^(*0)η) = 2.69±0.14±0.23, B(B̅^(0) → D^(0)ω) = 2.57±0.11±0.14, B(B̅^(0) → D^(*0)ω) = 4.55±0.24±0.39, B(B̅^(0)→D^(0)η′) = 1.48±0.13±0.07, and B(B̅^(0) → D^(*0)n′) = 1.49±0.22±0.15. We also present the first measurement of the longitudinal polarization fraction of the decay channel D*0ω, fL=(66.5±4.7±1.5)%. In the above, the first uncertainty is statistical and the second is systematic. The results are based on a sample of (454±5)×10^6 BB̅ pairs collected at the Υ(4S) resonance, with the BABAR detector at the PEP-II storage rings at SLAC. The measurements are the most precise determinations of these quantities from a single experiment. They are compared to theoretical predictions obtained by factorization, Soft Collinear Effective Theory (SCET) and perturbative QCD (pQCD). We find that the presence of final state interactions is favored and the measurements are in better agreement with SCET than with pQCD

Study of dipion bottomonium transitions and search for the h_b(1P) state

We study inclusive dipion decays using a sample of 108×10^6Υ(3S) events recorded with the BABAR detector. We search for the decay mode Υ(3S)→π^+π^-h_b(1P) and find no evidence for the bottomonium spin-singlet state h_b(1P) in the invariant mass distribution recoiling against the π^+π^- system. Assuming the h_b(1P) mass to be 9.900  GeV/c^2, we measure the upper limit on the branching fraction B[Υ(3S)→π^+π^-h_b(1P)]<1.2×10^(-4), at 90% confidence level. We also investigate the χ_(bJ)(2P)→π^+π^-χ_(bJ)(1P), Υ(3S)→π^+π^-Υ(2S), and Υ(2S)→π^+π^-Υ(1S) dipion transitions and present an improved measurement of the branching fraction of the Υ(3S)→π^+π^-Υ(2S) decay and of the Υ(3S)-Υ(2S) mass difference

B^0 meson decays to ρ^0K^(*0), f_0K^(*0), and ρ^-K^(*+), including higher K^* resonances

We present branching fraction measurements for the decays B^0→ρ^0K^(*0), B^0→f_0K^(*0), and B^0→ρ^-K^(*+), where K^* is an S-wave (Kπ)_0^* or a K^*(892) meson; we also measure B^0→f_0K_2^*(1430)^0. For the K^*(892) channels, we report measurements of longitudinal polarization fractions (for ρ final states) and direct CP violation asymmetries. These results are obtained from a sample of (471.0±2.8)×10^6 BB̅ pairs collected with the BABAR detector at the PEP-II asymmetric-energy e^+e^- collider at the SLAC National Accelerator Laboratory. We observe ρ^0K^*(892)^0, ρ^0(Kπ)_0^(*0), f_0K^*(892)^0, and ρ^-K^*(892)^+ with greater than 5σ significance, including systematics. We report first evidence for f_0(Kπ)_0^(*0) and f_0K_2^*(1430)^0, and place an upper limit on ρ^-(Kπ)_0^(*+). Our results in the K^*(892) channels are consistent with no direct CP violation

Measurement of the mass and width of the D_(s1)(2536)^+ meson

The decay width and mass of the D_(s1)(2536)^+ meson are measured via the decay channel D_(s1) + →D^(*+)K_(S)^0 using 385 fb^(-1) of data recorded with the BABAR detector in the vicinity of the Υ(4S) resonance at the PEP-II asymmetric-energy electron-positron collider. The result for the decay width is Γ(D_(s1)^+) = 0.92 ± 0.03(stat.) ± 0.04(syst.) MeV. For the mass, a value of m(D_(s1)^+) = 2535.08±0.01(stat.) ± 0.15(syst.) MeV/c^2 is obtained. The mass difference between the D_(s1)^+ and the D^(*+) is measured to be m(D_(s1)^+) - m(D^(*+)) = 524.83 ± 0.01(stat.) ± 0.04(syst.)  MeV/c^2, representing a significant improvement compared to the current world average. The unnatural spin-parity assignment for the D_(s1)^+ meson is confirmed

Search for the Z_1(4050)^+ and Z_2(4250)^+ states in B̅ ^0→χ_(c1)K^-π^+ and B^+→χ_(c1)K_S^0π^+

We search for the Z_1(4050)^+ and Z_2(4250)^+ states, reported by the Belle Collaboration, decaying to χ_(c1)π^+ in the decays B̅ ^0→χ_(c1)K^-π^+ and B^+→χ_(c1)K_S^0π^+ where χ_(c1)→J/ψγ. The data were collected with the BABAR detector at the SLAC PEP-II asymmetric-energy e^+e^- collider operating at center-of-mass energy 10.58 GeV, and correspond to an integrated luminosity of 429  fb^(-1). In this analysis, we model the background-subtracted, efficiency-corrected χ_(c1)π^+ mass distribution using the Kπ mass distribution and the corresponding normalized Kπ Legendre-polynomial moments, and then test the need for the inclusion of resonant structures in the description of the χ_(c1)π^+ mass distribution. No evidence is found for the Z_1(4050)^+ and Z_2(4250)^+ resonances, and 90% confidence level upper limits on the branching fractions are reported for the corresponding B-meson decay modes

Observation of the baryonic B decay B̅^0→Λ_c^+Λ̅ K^-

We report the observation of the baryonic B decay B̅ ^0→Λ_c^+Λ̅ K^- with a significance larger than 7 standard deviations based on 471×10^6 BB̅ pairs collected with the BABAR detector at the PEP-II storage ring at SLAC. We measure the branching fraction for the decay B̅ ^0→Λ_c^+Λ̅ K^- to be (3.8±0.8_(stat)±0.2_(sys)±1.0_(Λc)^+)×10^(-5). The uncertainties are statistical, systematic, and due to the uncertainty in the Λc+ branching fraction. We find that the Λ_c^+K^- invariant-mass distribution shows an enhancement above 3.5  GeV/c^2

Amplitude analysis of B^0 → K^+π^-π^0 and evidence of direct CP violation in B → K^* π decays

We analyze the decay B^0 → K^+π^-π^0 with a sample of 4.54×10^8 BB̅ events collected by the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC, and extract the complex amplitudes of seven interfering resonances over the Dalitz plot. These results are combined with amplitudes measured in B^0 → K_S^0π^+π^- decays to construct isospin amplitudes from B^0 → K^* π and B^0 → ρK decays. We measure the phase of the isospin amplitude Φ_(3/2), useful in constraining the Cabibbo-Kobayashi-Maskawa unitarity triangle angle γ and evaluate a CP rate asymmetry sum rule sensitive to the presence of new physics operators. We measure direct CP violation in B^0 → K^(*+)π^- decays at the level of 3σ when measurements from both B^0 → K^+π^-π^0 and B^0 → K_S^0π^+π^- decays are combined

Study of B → X_uℓv decays in BB events tagged by a fully reconstructed B-meson decay and determination of │V_(ub)│

We report measurements of partial branching fractions for inclusive charmless semileptonic B decays B → X_uℓν and the determination of the Cabibbo–Kobayashi–Maskawa (CKM) matrix element |V_(ub)|. The analysis is based on a sample of 467×10^6 Υ(4S)→BB decays recorded with the BABAR detector at the PEP-II e^+e^- storage rings. We select events in which the decay of one of the B mesons is fully reconstructed and an electron or a muon signals the semileptonic decay of the other B meson. We measure partial branching fractions ΔB in several restricted regions of phase space and determine the CKM element |V_(ub)| based on different QCD predictions. For decays with a charged lepton momentum p_ℓ^*>1.0  GeV in the B meson rest frame, we obtain ΔB=(1.80±0.13_(stat)±0.15_(sys)±0.02_(theo))×10^(-3) from a fit to the two-dimensional M_X-q^2 distribution. Here, M_X refers to the invariant mass of the final state hadron X and q^2 is the invariant mass squared of the charged lepton and neutrino. From this measurement we extract |V_(ub)|=(4.33±0.24_(exp)±0.15_(theo))×10^(-3) as the arithmetic average of four results obtained from four different QCD predictions of the partial rate. We separately determine partial branching fractions for B^0 and B^- decays and derive a limit on the isospin breaking in B → X_uℓν decays

Search for the decay D^0 → γγ and measurement of the branching fraction for D^0 → π^0π^0

We search for the rare decay of the D^0 meson to two photons, D^0→γγ, and present a measurement of the branching fraction for a D^0 meson decaying to two neutral pions, B(D^0→π^0π^0). The data sample analyzed corresponds to an integrated luminosity of 470.5  fb^(-1) collected by the BABAR detector at the PEP-II asymmetric-energy e^+e^- collider at SLAC. We place an upper limit on the branching fraction, B(D^0→γγ)<2.2×10^(-6), at 90% confidence level. This limit improves on the existing limit by an order of magnitude. We also find B(D^0→π^0π^0)=(8.4±0.1±0.4±0.3)×10^(-4)