Browsing by Author "Eigen, G."
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Item Branching Fraction and Form-Factor Shape Measurements of Exclusive Charmless Semileptonic B Decays, and Determination of |V_{ub}|(American Physical Society, 2012-11-05) Lees, J. P.; Poireau, V.; Tisserand, V.; Tico, J. Garra; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We report the results of a study of the exclusive charmless semileptonic decays, B0→π -+ν, B+ → π0⁺ν, B +→ω +ν, B +→η +ν, and B +→η ′+ν (=e or μ) undertaken with approximately 462×106 BB̄ pairs collected at the Υ(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions in several bins of q2, the square of the momentum transferred to the lepton-neutrino pair, for B0→π - +ν, B +→π0 +ν, B +→ω +ν, and B +→η +ν. From these distributions, we extract the form-factor shapes f +(q2) and the total branching fractions B(B0→π -+ν)=(1.45±0.04 stat±0.06 syst)×10 -4 (combined π - and π0 decay channels assuming isospin symmetry), B(B +→ω +ν)=(1.19±0.16 stat±0.09 syst)×10 -4 and B(B +→η +ν)=(0.38±0.05 stat±0.05 syst)×10 -4. We also measure B(B +→η ′+ν)=(0.24±0. 08 stat±0.03 syst)×10 -4. We obtain values for the magnitude of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |V ub| by direct comparison with three different QCD calculations in restricted q2 ranges of B→π +ν decays. From a simultaneous fit to the experimental data over the full q2 range and the FNAL/MILC lattice QCD predictions, we obtain |V ub|=(3.25±0.31)×10 -3, where the error is the combined experimental and theoretical uncertainty. © 2012 American Physical Society.Item Branching fraction of τ-→π-Ks0Ks0(π0)ν τ decays(American Physical Society, 2012-11-26) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We present a study of τ -→π -KS0KS0(π0) ν τ and τ -→K -KS0KS0(π0) ν τ decays using a data set of 430 million tau lepton pairs, corresponding to an integrated luminosity of 468 fb(-1), collected with the BABAR detector at the PEP-II asymmetric energy e(+)e(-) storage rings. We measure branching fractions of (2.31 +/- 0.04 +/- 0.08) x 10(-4) and (1.60 +/- 0.20 +/- 0.22) x 10(-5) for the τ -→π -KS0KS0ν τ and τ -→π -KS0KS0π0ν τ decays, respectively. We find no evidence for τ -→K -KS0KS0ν τ and τ -→K -KS0KS0π0ν τ decays and place upper limits on the branching fractions of 6.3 x 10(-7) and 4.0 x 10(-7) at the 90% confidence level.Item Evidence for an excess of B̄ → D^(*)_τ⁻ ν̅_τ decays(Amer Physical Soc, 2012-09-06) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 56366505900 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.Based on the full BABAR data sample, we report improved measurements of the ratios R(D^( *) = ℬ(B̄→D^( *)τ -ν {̄τ}) / ℬ(B̄→D^( *)ℓe̅ν ̅ℓ), where ℓ is either e or μ. These ratios are sensitive to new physics contributions in the form of a charged Higgs boson. We measure R(D*) = 0.440 ± 0.058 ± 0.042 and R(D*) = 0.332 ± 0.024 ± 0.018, which exceed the standard model expectations by 2.0σ and 2.7σ, respectively. Taken together, our results disagree with these expectations at the 3.4σ level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model.Item Measurement of Branching Fractions and Rate Asymmetries in the Rare Decays B → K^{(*)}ℓ⁺ℓ⁻(American Physical Society, 2012-08-24) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.In a sample of 471 x 106 BB̅ events collected with the BABAR detector at the PEP-II e⁺e⁻ collider we study the rare decays B → K^{(*)}ℓ⁺ℓ⁻, where ℓ⁺ℓ⁻ is either e⁺e⁻ or μ⁺μ⁻. We report results on partial branching fractions and isospin asymmetries in seven bins of dilepton mass-squared. We further present CP and lepton-flavor asymmetries for dilepton masses below and above the J/ψ resonance. We find no evidence for CP or lepton-flavor violation. The partial branching fractions and isospin asymmetries are consistent with the Standard Model predictions and with results from other experiments.Item Measurement of ℬ(B → Χ_sγ), the B → Χ_sγ Photon Energy Spectrum, and the Direct CP Asymmetry in B → Χ_{s+d}γ Decays.(American Physical Society, 2012-12-28) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.The photon spectrum in B → X{s}γ decay, where X{s} is any strange hadronic state, is studied using a data sample of (382.8 ± 4.2) x 10⁶ e⁺e⁻ → Υ(4S) → BB̅ events collected by the BABAR experiment at the PEP-II collider. The spectrum is used to measure the branching fraction ℬ(B → X{s}γ) = (3. 21 ± 0.15 ± 0.29 ± 0.08) x 10⁻⁴ and the first, second, and third moments E{γ} = 2.267 ± 0. 019 ± 0.032 ± 0.003 GeV, <(E{γ}) -- )² = 0.0484 ± 0.0053 ± 0.0077 ± 0.0005 GeV², and <(E{γ}) -- )³ = -0.0048 ± 0.0011 ± 0.0011± 0.0004 GeV3, for the range E{γ} > 1.8 GeV, where E{γ} is the photon energy in the B-meson rest frame. Results are also presented for narrower E{γ} ranges. In addition, the direct CP asymmetry A{CP}(B → X{s+d}γ) is measured to be 0.057 ± 0.063. The spectrum itself is also unfolded to the B-meson rest frame; that is the frame in which theoretical predictions for its shape are made.Item Observation of Time-Reversal Violation in the B⁰ Meson System(American Physical Society, 2012-11-19) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.Although CP violation in the B meson system has been well established by the B factories, there has been no direct observation of time-reversal violation. The decays of entangled neutral B mesons into definite flavor states (B⁰ or B̄⁰), and J/ψK_L⁰ or cc̄K_S⁰ final states (referred to as B₊ or B₋), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, B̅⁰ → B₋ and B₋ → B̅⁰, as a function of the time difference between the two B decays. Using 468 × 10⁶ BB̄ pairs produced in Υ(4S) decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding ΔS_T⁺ = -1.37 ± 0.14(stat) ± 0.06(syst) and ΔS_T⁻ = 1.17 ± 0.18(stat) ± 0.11(syst). These nonzero results represent the first direct observation of T violation through the exchange of initial and final states in transitions that can only be connected by a T-symmetry transformation.Item Precise Measurement of the e⁺e⁻ → π⁺π⁻ (γ) Cross Section with the Initial-State Radiation Method at BABAR(American Physical Society, 2012-08-28) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.A precise measurement of the cross section of the process e⁺e⁻ → π⁺π⁻ (γ) from threshold to an energy of 3 GeV is obtained with the initial-state radiation (ISR) method using 232 fb⁻¹ of data collected with the BABAR detector at e⁺e⁻ center-of-mass energies near 10.6 GeV. The ISR luminosity is determined from a study of the leptonic process e⁺e⁻ → μ⁺μ⁻ (γ) γ_{ISR}, which is found to agree with the next-to-leading-order QED prediction to within 1.1%. The cross section for the process e⁺e⁻ → π⁺π⁻ (γ) is obtained with a systematic uncertainty of 0.5% in the dominant ρ resonance region. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the measured π π cross section from threshold to 1.8 GeV is (514.1 ± 2.2(stat) ± 3.1(syst))×10⁻¹⁰.Item Precision Measurement of the B→X_sγ Photon Energy Spectrum, Branching Fraction, and Direct CP Asymmetry A_{CP}(B→X_{s+d}γ)(American Physical Society, 2012-11-09) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.The photon spectrum in the inclusive electromagnetic radiative decays of the B meson, B→X_sγ plus B→X_dγ, is studied using a data sample of (382.8 ± 4.2)×10⁶Υ(4S) →BB̄ decays collected by the BABAR experiment at SLAC. The spectrum is used to extract the branching fraction ℬ(B→X_sγ)=(3. 21 ± 0.33) ×10⁻⁴ for E_γ > 1.8 GeV and the direct CP asymmetry A_{CP} (B→X_{s+d}γ)=0. 057 ± 0.063. The effects of detector resolution and Doppler smearing are unfolded to measure the photon energy spectrum in the B meson rest frame.Item Search for Lepton-Number Violating Processes in B⁺ → h⁻ l⁺ l⁺ Decays(Amer Physical Soc, 2012-04-19) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We have searched for the lepton-number violating processes B +→h -- +- + with h -=K -/π - and - +=e +/μ +, using a sample of 471±3 million BB̄ events collected with the BABAR detector at the PEP-II e +e - collider at the SLAC National Accelerator Laboratory. We find no evidence for these decays and place 90%-confidence-level upper limits on their branching fractions B(B +→π -e +e +)<2.3×10 -8, B(B +→K -e +e +)<3.0×10 -8, B(B +→π -μ +μ +)<10. 7×10 -8, and B(B +→K -μ +μ +)<6.7×10 -8. © 2012 American Physical Society.Item Search for Resonances Decaying to η_c π+ π- in Two-Photon Interactions(American Physical Society, 2012-11-06) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We report a study of the process γγ→X→η cπ +π -, where X stands for one of the resonances χ c2(1P), η c(2S), X(3872), X(3915), or χ c2(2P). The analysis is performed with a data sample of 473.9fb -1 collected with the BABAR detector at the PEP-II asymmetric-energy electron-positron collider. We do not observe a significant signal for any channel, and calculate 90% confidence-level upper limits on the products of branching fractions and two-photon widths Γ X→γγB(X→η cπ +π -): 15.7eV for χ c2(1P), 133eV for η c(2S), 11.1eV for X(3872) (assuming it to be a spin-2 state), 16eV for X(3915) (assuming it to be a spin-2 state), and 18eV for χ c2(2P). We also report upper limits on the ratios of branching fractions B(η c(2S) →η cπ +π -)/B(η c(2S) →KS0K +π -)<10.0 and B(χ c2(1P) →η cπ +π -) /B(χ c2(1P)→KS0K +π -)<32.9 at the 90%confidence level. © 2012 American Physical Society.Item Search for the Decay Modes D⁰ → e⁺e⁻, D⁰ → μ⁺μ⁻, and D⁰ → e^{±} μ^{∓}(Amer Physical Soc, 2012-08-01) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We present searches for the rare decay modes D0→e +e -, D0→μ +μ -, and D0→e ±μ ∓ in continuum e +e -→cc̄ events recorded by the BABAR detector in a data sample that corresponds to an integrated luminosity of 468fb -1. These decays are highly Glashow-Iliopoulos-Maiani suppressed but may be enhanced in several extensions of the standard model. Our observed event yields are consistent with the expected backgrounds. An excess is seen in the D0→μ +μ - channel, although the observed yield is consistent with an upward background fluctuation at the 5% level. Using the Feldman-Cousins method, we set the following 90% confidence level intervals on the branching fractions: B(D0→e +e -)<1. 7×10 -7, B(D0→μ +μ -) within 0.6, 8.1]×10 -7, and B(D0→e ±μ ∓)<3.3×10 -7. © 2012 American Physical Society.Item Study of High-Multiplicity Three-Prong and Five-Prong τ Decays at BABAR(Amer Physical Soc, 2012-11-27) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We present measurements of the branching fractions of three-prong and five-prong τ decay modes using a sample of 430million τ lepton pairs, corresponding to an integrated luminosity of 468fb -1, collected with the BABAR detector at the PEP-II asymmetric-energy e +e - storage rings at SLAC National Accelerator Laboratory. The τ -→(3π) -ην τ, τ -→(3π) -ων τ, and τ -→π -f 1(1285)ν τ branching fractions are presented, as well as a new limit on the branching fraction of the second-class current decay τ -→π -η ′(958)ν τ. We search for the decay mode τ -→K -η ′(958) ν τ and for five-prong decay modes with kaons, and place the first upper limits on their branching fractions. © 2012 American Physical Society.Item Study of the baryonic B decay B⁻ → Σ_{c ^{++}} ρ̅π⁻ π⁻(American Physical Society, 2012-11-19) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We report the measurement of the baryonic B decay B-→Σc++p̅ π-π-. Using a data sample of 467×106 BB̅ pairs collected with the BABAR detector at the PEP-II storage ring at SLAC, the measured branching fraction is (2.98±0.16(stat)±0.15(syst)±0.77(Λc))×10-4, where the last error is due to the uncertainty in B(Λc+→pK-π+). The data suggest the existence of resonant subchannels B-→Λc(2595)+p̅ π- and, possibly, B-→Σc++Δ̅ --π-. We see unexplained structures in m(Σc++π-π-) at 3.25 GeV/c2, 3.8 GeV/c2, and 4.2 GeV/c2.Item Study of the Reaction e⁺e⁻ -→ J/ψ π⁺π⁻ via Initial-State Radiation at BABAR(American Physical Society, 2012-09-12) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We study the process e⁺e⁻ → J/ψ π⁺π⁻ with initial-state-radiation events produced at the PEP-II asymmetric-energy collider. The data were recorded with the BABAR detector at center-of-mass energies 10.58 and 10.54 GeV, and correspond to an integrated luminosity of 454 fb⁻¹. We investigate the J/ψ π⁺π⁻ mass distribution in the region from 3.5 to 5.5 GeV/c². Below 3.7 GeV/c² the ψ(2S) signal dominates, and above 4 GeV/c² there is a significant peak due to the Y(4260). A fit to the data in the range 3.74-5.50 GeV/c² yields a mass value 4245 ±5(stat) ±4(syst) MeV/c² and a width value 114{_-15 ^{+16}} (stat) ±7(syst) MeV for this state. We do not confirm the report from the Belle Collaboration of a broad structure at 4.01 GeV/c². In addition, we investigate the π⁺π⁻ system which results from Y(4260) decay.