Search Results (288 total)

We perform a time-dependent and time-integrated angular analysis of the decays B⁰→φK^*(892)⁰, φK₂^*(1430)⁰, and φ(Kπ)₀^*0 with the final sample of about 465×10⁶ BB̅ pairs recorded with the BABAR detector. Twenty-four parameters are investigated, including the branching fractions, CP-violation parameters, and parameters sensitive to final-state interactions. We use the dependence on the Kπ invariant mass of the interference between the scalar and vector or tensor components to resolve discrete ambiguities of the strong and weak phases. We use the time evolution of the B→φK_S⁰π⁰ channel to extract the CP-violation phase difference Δϕ₀₀=0.28±0.42±0.04 between the B and B̅ decay amplitudes. When the B→φK^±π^∓ channel is included, the fractions of longitudinal polarization f_L of the vector-vector and vector-tensor decay modes are measured to be 0.494±0.034±0.013 and 0.901_-0.058^+0.046±0.037, respectively. This polarization pattern requires the presence of a positive-helicity amplitude in the vector-vector decay from a currently unknown source.

We report a search for the decays B^-→K⁺π^-π^- and B^-→K^-K^-π⁺, which are highly suppressed in the standard model. Using a sample of (467±5)×10⁶ BB̅ pairs collected with the BABAR detector, we do not see any evidence of these decays and determine 90% confidence level upper limits of B(B^-→K⁺π^-π^-)<9.5×10^-7 and B(B^-→K^-K^-π⁺)<1.6×10^-7 on the corresponding branching fractions, including systematic uncertainties.

We present the results of searches for B decays to charmless final states involving ϕ, f₀(980), and charged or neutral ρ mesons. The data sample corresponds to 384×10⁶ BB̅ pairs collected with the BABAR detector operating at the PEP-II asymmetric-energy e⁺e^- collider at SLAC. We find no significant signals and determine the following 90% confidence level upper limits on the branching fractions, including systematic uncertainties: B(B⁰→ϕϕ)<2.0×10^-7, B(B⁺→ϕρ⁺)<30×10^-7, B(B⁰→ϕρ⁰)<3.3×10^-7, B[B⁰→ϕf₀(980)]×B[f₀(980)→π⁺π^-]<3.8×10^-7, and B[B⁰→f₀(980)f₀(980)]×B[f₀(980)→π⁺π^-]×B[f₀(980)→K⁺K^-]<2.3×10^-7.

We report a study of B^±→D^*K^± decays with D^* decaying to Dπ⁰ or Dγ, using 383×10⁶ BB̅ pairs collected at the Υ(4S) resonance with the BABAR detector at the SLAC PEP-II B Factory. The D meson decays under study include a non-CP mode (K^±π^∓), CP-even modes (K^±K^∓,π^±π^∓), and CP-odd modes (K_S⁰π⁰,K_S⁰ϕ,K_S⁰ω). We measure ratios (R_CP±^*) of branching fractions of decays to CP eigenmode states and to flavor-specific states as well as CP asymmetries (A_CP±^*). These measurements are sensitive to the unitarity triangle angle γ. We obtain A_CP+^*=-0.11±0.09±0.01, R_CP+^*=1.31±0.13±0.04, and A_CP-^*=0.06±0.10±0.02, R_CP-^*=1.10±0.12±0.04, where the first error is statistical and the second error is systematic. Translating our results into an alternative parametrization, widely used for related measurements, we obtain x₊^*=0.11±0.06±0.02 and x_-^*=0.00±0.06±0.02. No significant CP-violating charge asymmetry is found in either the flavor-specific mode D→K^±π^∓ or in B^±→D^*π^± decays.

We present the observation of the decay B⁰→χ_c0K^*0 as well as evidence of B⁺→χ_c0K^*+, with an 8.9 and a 3.6 standard deviation significance, respectively, using a data sample of 454×10⁶ Υ(4S)→BB̅ decays collected with the BABAR detector at the PEP-II B meson factory located at the Stanford Linear Accelerator Center (SLAC). The measured branching fractions are B(B⁰→χ_c0K^*0)=(1.7±0.3±0.2)×10^-4 and B(B⁺→χ_c0K^*+)=(1.4±0.5±0.2)×10^-4, where the first quoted errors are statistical and the second are systematic. We obtain a branching fraction upper limit of B(B⁺→χ_c0K^*+)<2.1×10^-4 at the 90% confidence level.

We present a search for the decays B→K^*νν̅ using 454×10⁶BB̅ pairs collected at the Υ(4S) resonance with the BABAR detector at the SLAC PEP-II B-Factory. We first select an event sample where one B is reconstructed in a semileptonic or hadronic mode with one charmed meson. The remaining particles in the event are then examined to search for a B→K^*νν̅ decay. The charged K^* is reconstructed as K^*+→K_S⁰π⁺ or K^*+→K⁺π⁰; the neutral K^* is identified in K^*0→K⁺π^- mode. We establish upper limits at 90% confidence level of B(B⁺→K^*+νν̅ )<8×10^-5, B(B⁰→K^*0νν̅ )<12×10^-5, and B(B→K^*νν̅ )<8×10^-5.

We perform a measurement of the CP asymmetry in b→sγ decays using a sample of 383×10⁶ BB̅ events collected by the BABAR detector at the SLAC PEP-II asymmetric B factory. We reconstruct 16 flavor-specific B decay modes containing a high-energy photon and a hadronic system X_s containing an s quark. We measure the CP asymmetry to be -0.011±0.030(stat)±0.014(syst) for a hadronic system mass between 0.6 and 2.8  GeV/c².

We study B⁰→ρ⁰ρ⁰ decays in a sample of 465×10⁶ Υ(4S)→BB̅ events collected with the BABAR detector at the PEP-II asymmetric-energy e⁺e^- collider located at the Stanford Linear Accelerator Center (SLAC). We measure the branching fraction B=(0.92±0.32±0.14)×10^-6 and longitudinal polarization fraction f_L=0.75_-0.14^+0.11±0.05, where the first uncertainty is statistical and the second is systematic. The evidence for the B⁰→ρ⁰ρ⁰ signal has a significance of 3.1 standard deviations, including systematic uncertainties. We investigate the proper-time dependence of the longitudinal component in the decay and measure the CP-violating coefficients S_L⁰⁰=(0.3±0.7±0.2) and C_L⁰⁰=(0.2±0.8±0.3). We study the implication of these results for the unitarity triangle angle α.

We report the first observation of e⁺e^-→ρ⁺ρ^-, in a data sample of 379  fb^-1 collected with the BABAR detector at the PEP-II e⁺e^- storage ring at center-of-mass energies near sqrt[s]=10.58  GeV. We measure a cross section of σ(e⁺e^-→ρ⁺ρ^-)=8.3±0.7(stat)±0.8(syst)  fb within the range of |cos⁡θ^*|<0.8 and |cos⁡θ_±|<0.85, where θ^* is the center-of-mass polar angle of the ρ^± meson and θ_± are the angles in the ρ^± rest frame between the direction of the boost from the laboratory frame and the direction of the π^±. Assuming production through single-photon annihilation, there are three independent helicity amplitudes. We measure the ratios of their squared moduli to be |F₀₀|²∶|F₁₀|²∶|F₁₁|²=  0.51±0.14(stat)±0.07(syst)∶0.10±0.04(stat)±0.01(syst)∶0.04±0.03(stat)±0.01(syst). The |F₀₀|² result is inconsistent with the prediction of 1.0 made by QCD models with a significance of 3.1 standard deviations including systematic uncertainties.

With the full BABAR data sample of 465×10⁶ BB̅ pairs, we observe the decays B^±→φK₁(1270)^± and B^±→φK₂^*(1430)^±. We measure the branching fractions (6.1±1.6±1.1)×10^-6 and (8.4±1.8±1.0)×10^-6 and the fractions of longitudinal polarization 0.46_-0.13-0.07^+0.12+0.06 and 0.80_-0.10^+0.09±0.03, respectively. We also report on the B^±→φK₀^*(1430)^± decay branching fraction of (7.0±1.3±0.9)×10^-6 and several parameters sensitive to CP violation and interference in the above three decays. Upper limits are placed on the B^± decay rates to final states with φ and K₁(1400)^±, K^*(1410)^±, K₂(1770)^±, or K₂(1820)^±. Understanding the observed polarization pattern requires amplitude contributions from an uncertain source.

We measure the time-dependent CP asymmetry in B⁰→K_S⁰π⁰γ decays for two regions of K_S⁰-π⁰ invariant mass, m(K_S⁰π⁰), using the final BABAR data set of 467×10⁶ BB̅ pairs collected at the PEP-II e⁺e^- collider at SLAC. We find 339±24 B⁰→K^*0γ candidates and measure S_K^*γ=-0.03±0.29±0.03 and C_K^*γ=-0.14±0.16±0.03. In the range 1.1<m(K_S⁰π⁰)<1.8  GeV/c² we find 133±20 B⁰→K_S⁰π⁰γ candidates and measure S_KS⁰π⁰γ=-0.78±0.59±0.09 and C_KS⁰π⁰γ=-0.36±0.33±0.04. The uncertainties are statistical and systematic, respectively.

We study the thermodynamics and the pair structure of hard, infinitely thin, circular platelets in the isotropic phase. Monte Carlo simulation results indicate a rich spatial structure of the spherical expansion components of the direct correlation function, including nonmonotonical variation of some of the components with density. Integral equation theory is shown to reproduce the main features observed in simulations. The hypernetted chain closure, as well as its extended versions that include the bridge function up to second and third order in density, perform better than both the Percus-Yevick closure and Verlet bridge function approximation. Using a recent fundamental measure density functional theory, an analytic expression for the direct correlation function is obtained as the sum of the Mayer bond and a term proportional to the density and the intersection length of two platelets. This is shown to give a reasonable estimate of the structure found in simulations, but to fail to capture the nonmonotonic variation with density. We also carry out a density functional stability analysis of the isotropic phase with respect to nematic ordering and show that the limiting density is consistent with that where the Kerr coefficient vanishes. As a reference system, we compare to simulation results for hard oblate spheroids with small, but nonzero elongations, demonstrating that the case of vanishingly thin platelets is approached smoothly.

We present a measurement of the branching fractions for the Cabibbo-favored radiative decay D⁰→K̅ ^*0γ and the Cabibbo-suppressed radiative decay D⁰→ϕγ. These measurements are based on a data sample corresponding to an integrated luminosity of 387.1  fb^-1 and recorded with the BABAR detector at the PEP-II e⁺e^- asymmetric-energy collider operating at center-of-mass energies 10.58 and 10.54 GeV. We measure the branching fractions relative to the well-studied decay D⁰→K^-π⁺ and find B(D⁰→K̅ ^*0γ)/B(D⁰→K^-π⁺)=(8.43±0.51±0.70)×10^-3 and B(D⁰→ϕγ)/B(D⁰→K^-π⁺)=(7.15±0.78±0.69)×10^-4, where the first error is statistical and the second is systematic. This is the first observation of the decay mode D⁰→K̅ ^*0γ.

We report the results of a search for the decay B⁰→K^*+K^*- with a sample of 454±5 million BB̅ pairs collected with the BABAR detector at the PEP-II asymmetric-energy e⁺e^- collider at the Stanford Linear Accelerator Center. We obtain an upper limit at the 90% confidence level on the branching fraction for B(B⁰→K^*+K^*-)<2.0×10^-6, assuming the decay is fully longitudinally polarized.

Using 385  fb^-1 of e⁺e^- collision data collected at center-of-mass energies around 10.6 GeV, we search for time-integrated CP violation in the Cabibbo-suppressed decays D⁰/D̅ ⁰→π^-π⁺π⁰ and D⁰/D̅ ⁰→K^-K⁺π⁰ with both model-independent and model-dependent methods. Measurements of the asymmetries in amplitudes of flavor states and CP eigenstates provide constraints on theories beyond the standard model, some of which predict CP violation in amplitudes at the 1% level or higher. We find no evidence of CP violation and hence no conflict with the standard model.

We report a Dalitz-plot analysis of the charmless hadronic decays of neutral B mesons to K^±π^∓π⁰. With a sample of (231.8±2.6)×10⁶Υ(4S)→BB̅ decays collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, we measure the magnitudes and phases of the intermediate resonant and nonresonant amplitudes for B⁰ and B̅ ⁰ decays and determine the corresponding CP-averaged branching fractions and charge asymmetries. The inclusive branching fraction and CP-violating charge asymmetry are measured to be B(B⁰→K⁺π^-π⁰)=(35.7_-1.5^+2.6±2.2)×10^-6 and A_CP=-0.030_-0.051^+0.045±0.055 where the first errors are statistical and the second systematic. We observe the decay B⁰→K^*0(892)π⁰ with the branching fraction B(B⁰→K^*0(892)π⁰)=(3.6_-0.8^+0.7±0.4)×10^-6. This measurement differs from zero by 5.6 standard deviations (including the systematic uncertainties). The selected sample also contains B⁰→D̅ ⁰π⁰ decays where D̅ ⁰→K⁺π^-, and we measure B(B⁰→D̅ ⁰π⁰)=(2.93±0.17±0.18)×10^-4.

Using 214  fb^-1 of data recorded by the BABAR detector at the PEPII electron-positron collider, we study the decay D_s⁺→K⁺K^-e⁺ν_e. Except for a small S-wave contribution, the events with K⁺K^- masses in the range 1.01–1.03  GeV/c² correspond to ϕ mesons. For D_s⁺→ϕe⁺ν_e decays, we measure the relative normalization of the Lorentz invariant form factors at q²=0, r_V=V(0)/A₁(0)=1.849±0.060±0.095, r₂=A₂(0)/A₁(0)=0.763±0.071±0.065 and the pole mass of the axial-vector form factors m_A=(2.28_-0.18^+0.23±0.18)  GeV/c². Within the same K⁺K^- mass range, we also measure the relative branching fraction B(D_s⁺→K⁺K^-e⁺ν_e)/B(D_s⁺→K⁺K^-π⁺)=0.558±0.007±0.016, from which we obtain the total branching fraction B(D_s⁺→ϕe⁺ν_e)=(2.61±0.03±0.08±0.15)×10^-2. By comparing this value with the predicted decay rate, we extract A₁(0)=0.607±0.011±0.019±0.018. The stated uncertainties are statistical, systematic, and from external inputs.

Using 383×10⁶ BB̅ pairs from the BABAR data sample, we report results for branching fractions of six charged B-meson decay modes, where a charged kaon recoils against a charmless resonance decaying to KK̅ ^* or ηππ final states with mass in the range (1.2–1.8)  GeV/c². We observe a significant enhancement at the low KK̅ ^* invariant mass which is interpreted as B⁺→η(1475)K⁺, find evidence for the decay B⁺→η(1295)K⁺, and place upper limits on the decays B⁺→η(1405)K⁺, B⁺→f₁(1285)K⁺, B⁺→f₁(1420)K⁺, and B⁺→ϕ(1680)K⁺.

We report measurements of branching fractions for the decays B→Pℓν_ℓ, where P are the pseudoscalar charmless mesons π^-, π⁰, η and η^′, based on 348  fb^-1 of data collected with the BABAR detector, using B⁰ and B⁺ mesons found in the recoil of a second B meson decaying as B→D^(*)ℓν_ℓ. Assuming isospin symmetry, we combine pionic branching fractions to obtain B(B⁰→π^-ℓ⁺ν_ℓ)=(1.54±0.17_(stat)±0.09_(syst))×10^-4; we find 3.2σ evidence of the decay B⁺→ηℓ⁺ν_ℓ and measure its branching fraction to be (0.64±0.20_(stat)±0.03_(syst))×10^-4, and determine B(B⁺→η^′ℓ⁺ν_ℓ)<0.47×10^-4 to 90% confidence level. Using partial branching fractions for the pionic decays in ranges of the momentum transfer and a variety of form factor calculation, we obtain values of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element |V_ub| in ranging from 3.6×10^-3 to 4.1×10^-3.

We report on an improved measurement of the Cabibbo-Kobayashi-Maskawa CP-violating phase γ through a Dalitz plot analysis of neutral D meson decays to K_S⁰π⁺π^- and K_S⁰K⁺K^- produced in the processes B^∓→DK^∓, B^∓→D^*K^∓ with D^*→Dπ⁰, Dγ, and B^∓→DK^*∓ with K^*∓→K_S⁰π^∓. Using a sample of 383×10⁶ BB̅ pairs collected by the BABAR detector, we measure γ=(76±22±5±5)° (mod 180°), where the first error is statistical, the second is the experimental systematic uncertainty, and the third reflects the uncertainty on the description of the Dalitz plot distributions. The corresponding 2-standard-deviation region is 29°<γ<122°. This result has a significance of direct CP violation (γ≠0) of 3.0 standard deviations.

We present a study of the decays B^0,+→J/ψωK^0,+ using 383×10⁶ BB̅ events obtained with the BABAR detector at PEP-II. We observe Y(3940)→J/ψω, with mass 3914.6_-3.4^+3.8(stat)±2.0(syst)  MeV/c², and width 34_-8⁺¹²(stat)±5(syst)  MeV. The ratio of B⁰ and B⁺ decay to YK is 0.27_-0.23^+0.28(stat)_-0.01^+0.04(syst), and the relevant B⁰ and B⁺ branching fractions are reported.

We report the results of a search for the bottomonium ground state η_b(1S) in the photon energy spectrum with a sample of (109±1) million of Υ(3S) recorded at the Υ(3S) energy with the BABAR detector at the PEP-II B factory at SLAC. We observe a peak in the photon energy spectrum at E_γ=921.2_-2.8^+2.1(stat)±2.4(syst)  MeV with a significance of 10 standard deviations. We interpret the observed peak as being due to monochromatic photons from the radiative transition Υ(3S)→γη_b(1S). This photon energy corresponds to an η_b(1S) mass of 9388.9_-2.3^+3.1(stat)±2.7(syst)  MeV/c². The hyperfine Υ(1S)-η_b(1S) mass splitting is 71.4_-3.1^+2.3(stat)±2.7(syst)  MeV/c². The branching fraction for this radiative Υ(3S) decay is estimated to be [4.8±0.5(stat)±1.2(syst)]×10^-4.

The properties of the Ξ(1530) resonance are investigated in the Λ_c⁺→Ξ^-π⁺K⁺ decay process. The data sample was collected with the BABAR detector at the SLAC PEP-II asymmetric-energy e⁺e^- collider operating at center-of-mass energies 10.58 and 10.54 GeV. The corresponding integrated luminosity is approximately 230  fb^-1. The spin of the Ξ(1530) is established to be 3/2. The existence of an S-wave amplitude in the Ξ^-π⁺ system is inferred, and its interference with the Ξ(1530)⁰ amplitude provides the first clear demonstration of the Breit-Wigner phase motion expected for the Ξ(1530). The P₁(cos⁡θ_Ξ^-) Legendre polynomial moment indicates the presence of a significant S-wave amplitude for Ξ^-π⁺ mass values above 1.6  GeV/c², and a dip in the mass distribution at approximately 1.7  GeV/c² is interpreted as due to the coherent addition of a Ξ(1690)⁰ contribution to this amplitude. This would imply J^P=1/2^- for the Ξ(1690). Attempts at fitting the Ξ(1530)⁰ line shape yield unsatisfactory results, and this failure is attributed to interference effects associated with the amplitudes describing the K⁺π⁺ and/or Ξ^-K⁺ systems.

We report the measurement of the branching fractions of the rare decays B⁰→D_s^(*)+π^-, B⁰→D_s^(*)+ρ^-, and B⁰→D_s^(*)-K^(*)+ in a sample of 381×10⁶Υ(4S) decays into BB̅ pairs collected with the BABAR detector at the PEP-II asymmetric-energy e⁺e^- storage ring. We present evidence for the decay B⁰→D_s^-K^*+ and the vector-vector decays B⁰→D_s^*+ρ^- and B⁰→D_s^*-K^*+, as well as the first measurement of the vector meson polarization in these decays. We also determine the ratios of the CKM-suppressed to CKM-favored amplitudes r(D^(*)π) and r(D^(*)ρ) in decays B⁰→D^(*)±π^∓ and B⁰→D^(*)±ρ^∓, and comment on the prospects for measuring the CP observable sin⁡(2β+γ).

We present measurements of branching fractions for five B-meson decays to two-body charmless final states. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 459×10⁶ BB̅ pairs. The results for branching fractions are, in units of 10^-6 (upper limits at 90% C.L.), B(B⁺→ηρ⁺)=9.9±1.2±0.8, B(B⁰→η^′η)=0.5±0.4±0.1(<1.2), B(B⁰→ηπ⁰)=0.9±0.4±0.1(<1.5), B(B⁰→η^′π⁰)=0.9±0.4±0.1(<1.5), and B(B⁰→ωπ⁰)=0.07±0.26±0.02(<0.5). The first error quoted is statistical and the second systematic. For the ηρ⁺ mode, we measure the charge asymmetry A_ch(B⁺→ηρ⁺)=0.13±0.11±0.02.