K. J. Knoepfel

Publications (257)368.5 Total impact

• Article: Study of B̅ →Xuℓν̅ decays in BB̅ events tagged by a fully reconstructed B-meson decay and determination of |Vub|

  J. P. Lees, V. Poireau, V. Tisserand, J. Garra Tico, E. Grauges, M. Martinelli, D. A. Milanes, A. Palano, M. Pappagallo, G. Eigen, [......], N. Tasneem, T. J. Gershon, P. F. Harrison, T. E. Latham, E. M. T. Puccio, H. R. Band, S. Dasu, Y. Pan, R. Prepost, S. L. Wu
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  ABSTRACT: We report measurements of partial branching fractions for inclusive charmless semileptonic B decays B̅ →Xuℓν̅ and the determination of the Cabibbo–Kobayashi–Maskawa (CKM) matrix element |Vub|. The analysis is based on a sample of 467×106 Υ(4S)→BB̅ 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 |Vub| based on different QCD predictions. For decays with a charged lepton momentum pℓ*>1.0 GeV in the B meson rest frame, we obtain ΔB=(1.80±0.13stat±0.15sys±0.02theo)×10-3 from a fit to the two-dimensional MX-q2 distribution. Here, MX refers to the invariant mass of the final state hadron X and q2 is the invariant mass squared of the charged lepton and neutrino. From this measurement we extract |Vub|=(4.33±0.24exp⁡±0.15theo)×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 B̅ 0 and B- decays and derive a limit on the isospin breaking in B̅ →Xuℓν̅ decays.
  Phys. Rev. D. 08/2012; 86(3).
• Article: Cross sections for the reactions e+e-→K+K-π+π-, K+K-π0π0, and K+K-K+K- measured using initial-state radiation events

  J. P. Lees, V. Poireau, E. Prencipe, V. Tisserand, J. Garra Tico, E. Grauges, M. Martinelli, D. A. Milanes, A. Palano, M. Pappagallo, [......], T. J. Gershon, P. F. Harrison, T. E. Latham, E. M. T. Puccio, H. R. Band, S. Dasu, Y. Pan, R. Prepost, C. O. Vuosalo, S. L. Wu
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  ABSTRACT: We study the processes e+e-→K+K-π+π-γ, K+K-π0π0γ, and K+K-K+K-γ, where the photon is radiated from the initial state. About 84 000, 8000, and 4200 fully reconstructed events, respectively, are selected from 454 fb-1 of BABAR data. The invariant mass of the hadronic final state defines the e+e- center-of-mass energy, so that the K+K-π+π-γ data can be compared with direct measurements of the e+e-→K+K-π+π- reaction. No direct measurements exist for the e+e-→K+K-π0π0 or e+e-→K+K-K+K- reactions, and we present an update of our previous result based on a data sample that is twice as large. Studying the structure of these events, we find contributions from a number of intermediate states and extract their cross sections. In particular, we perform a more detailed study of the e+e-→ϕ(1020)ππγ reaction and confirm the presence of the Y(2175) resonance in the ϕ(1020)f0(980) and K+K-f0(980) modes. In the charmonium region, we observe the J/ψ in all three final states and in several intermediate states, as well as the ψ(2S) in some modes, and measure the corresponding products of branching fraction and electron width.
  Phys. Rev. D. 07/2012; 86(1).
• Article: Search for the decay modes B±→h±τℓ

  J. P. Lees, V. Poireau, V. Tisserand, J. Garra Tico, E. Grauges, D. A. Milanes, A. Palano, M. Pappagallo, G. Eigen, B. Stugu, [......], N. Tasneem, T. J. Gershon, P. F. Harrison, T. E. Latham, E. M. T. Puccio, H. R. Band, S. Dasu, Y. Pan, R. Prepost, S. L. Wu
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  ABSTRACT: We present a search for the lepton flavor violating decay modes B±→h±τℓ (h=K, π; ℓ=e, μ) using the BABAR data sample, which corresponds to 472×106 BB̅ pairs. The search uses events where one B meson is fully reconstructed in one of several hadronic final states. Using the momenta of the reconstructed B, h, and ℓ candidates, we are able to fully determine the τ four-momentum. The resulting τ candidate mass is our main discriminant against combinatorial background. We see no evidence for B±→h±τℓ decays and set a 90% confidence level upper limit on each branching fraction at the level of a few times 10-5.
  Phys. Rev. D. 07/2012; 86(1).
• Article: Study of CP violation in Dalitz-plot analyses of B0→K+K-KS0, B+→K+K-K+, and B+→KS0KS0K+

  J. P. Lees, V. Poireau, V. Tisserand, J. Garra Tico, E. Grauges, D. A. Milanes, A. Palano, M. Pappagallo, G. Eigen, B. Stugu, [......], N. Tasneem, T. J. Gershon, P. F. Harrison, T. E. Latham, E. M. T. Puccio, H. R. Band, S. Dasu, Y. Pan, R. Prepost, S. L. Wu
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  ABSTRACT: We perform amplitude analyses of the decays B0→K+K-KS0, B+→K+K-K+, and B+→KS0KS0K+, and measure CP-violating parameters and partial branching fractions. The results are based on a data sample of approximately 470×106 BB̅ decays, collected with the BABAR detector at the PEP-II asymmetric-energy B factory at the SLAC National Accelerator Laboratory. For B+→K+K-K+, we find a direct CP asymmetry in B+→ϕ(1020)K+ of ACP=(12.8±4.4±1.3)%, which differs from zero by 2.8σ. For B0→K+K-KS0, we measure the CP-violating phase βeff(ϕ(1020)KS0)=(21±6±2)°. For B+→KS0KS0K+, we measure an overall direct CP asymmetry of ACP=(4-5+4±2)%. We also perform an angular-moment analysis of the three channels and determine that the fX(1500) state can be described well by the sum of the resonances f0(1500), f2′(1525), and f0(1710).
  Phys. Rev. D. 06/2012; 85(11).
• Article: Observation and study of the baryonic B-meson decays B→D(*)pp̅ (π)(π)

  P. del Amo Sanchez, J. P. Lees, V. Poireau, E. Prencipe, V. Tisserand, J. Garra Tico, E. Grauges, M. Martinelli, A. Palano, M. Pappagallo, [......], P. F. Harrison, T. E. Latham, E. M. T. Puccio, H. R. Band, S. Dasu, K. T. Flood, Y. Pan, R. Prepost, C. O. Vuosalo, S. L. Wu
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  ABSTRACT: We present results for B-meson decay modes involving a charm meson, protons, and pions using 455×106 BB̅ pairs recorded by the BaBar detector at the SLAC PEP-II asymmetric-energy e+e- collider. The branching fractions are measured for the following ten decays: B̅ 0→D0pp̅ , B̅ 0→D*0pp̅ , B̅ 0→D+pp̅ π-, B̅ 0→D*+pp̅ π-, B-→D0pp̅ π-, B-→D*0pp̅ π-, B̅ 0→D0pp̅ π-π+, B̅ 0→D*0pp̅ π-π+, B-→D+pp̅ π-π-, and B-→D*+pp̅ π-π-. The four B- and the two five-body B̅ 0 modes are observed for the first time. The four-body modes are enhanced compared to the three- and the five-body modes. In the three-body modes, the M(pp̅ ) and M(D(*)0p) invariant-mass distributions show enhancements near threshold values. In the four-body mode B̅ 0→D+pp̅ π-, the M(pπ-) distribution shows a narrow structure of unknown origin near 1.5 GeV/c2. The distributions for the five-body modes, in contrast to the others, are similar to the expectations from uniform phase-space predictions.
  Phys. Rev. D. 05/2012; 85(9).
• Article: B0 meson decays to ρ0K*0, f0K*0, and ρ-K*+, including higher K* resonances

  J. P. Lees, V. Poireau, V. Tisserand, J. Garra Tico, E. Grauges, M. Martinelli, D. A. Milanes, A. Palano, M. Pappagallo, G. Eigen, [......], T. J. Gershon, P. F. Harrison, T. E. Latham, E. M. T. Puccio, H. R. Band, S. Dasu, Y. Pan, R. Prepost, C. O. Vuosalo, S. L. Wu
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  ABSTRACT: We present branching fraction measurements for the decays B0→ρ0K*0, B0→f0K*0, and B0→ρ-K*+, where K* is an S-wave (Kπ)0* or a K*(892) meson; we also measure B0→f0K2*(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)×106 BB̅ pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at the SLAC National Accelerator Laboratory. We observe ρ0K*(892)0, ρ0(Kπ)0*0, f0K*(892)0, and ρ-K*(892)+ with greater than 5σ significance, including systematics. We report first evidence for f0(Kπ)0*0 and f0K2*(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.
  Phys. Rev. D. 04/2012; 85(7).
• Article: Amplitude analysis and measurement of the time-dependent CP asymmetry of B0→KS0KS0KS0 decays

  J. P. Lees, V. Poireau, V. Tisserand, J. Garra Tico, E. Grauges, M. Martinelli, D. A. Milanes, A. Palano, M. Pappagallo, G. Eigen, [......], N. Tasneem, T. J. Gershon, P. F. Harrison, T. E. Latham, E. M. T. Puccio, H. R. Band, S. Dasu, Y. Pan, R. Prepost, S. L. Wu
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  ABSTRACT: We present the first results on the Dalitz-plot structure and improved measurements of the time-dependent CP-violation parameters of the process B0→KS0KS0KS0 obtained using 468×106 BB̅ decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. The Dalitz-plot structure is probed by a time-integrated amplitude analysis that does not distinguish between B0and B̅ 0 decays. We measure the total inclusive branching fraction B(B0→KS0KS0KS0)=(6.19±0.48±0.15±0.12)×10-6, where the first uncertainty is statistical, the second is systematic, and the third represents the Dalitz-plot signal model dependence. We also observe evidence for the intermediate resonant states f0(980), f0(1710), and f2(2010). Their respective product branching fractions are measured to be (2.70-1.19+1.25±0.36±1.17)×10-6, (0.50-0.24+0.46±0.04±0.10)×10-6, and (0.54-0.20+0.21±0.03±0.52)×10-6. Additionally, we determine the mixing-induced CP-violation parameters to be S=-0.94-0.21+0.24±0.06 and C=-0.17±0.18±0.04, where the first uncertainty is statistical and the second is systematic. These values are in agreement with the standard model expectation. For the first time, we report evidence of CP violation in B0→KS0KS0KS0 decays; CP conservation is excluded at 3.8 standard deviations including systematic uncertainties.
  Phys. Rev. D. 03/2012; 85(5).
• Article: Search for the Z1(4050)+ and Z2(4250)+ states in B̅ 0→χc1K-π+ and B+→χc1KS0π+

  J. P. Lees, V. Poireau, V. Tisserand, J. Garra Tico, E. Grauges, M. Martinelli, D. A. Milanes, A. Palano, M. Pappagallo, G. Eigen, [......], N. Tasneem, T. J. Gershon, P. F. Harrison, T. E. Latham, E. M. T. Puccio, H. R. Band, S. Dasu, Y. Pan, R. Prepost, S. L. Wu
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  ABSTRACT: We search for the Z1(4050)+ and Z2(4250)+ states, reported by the Belle Collaboration, decaying to χc1π+ in the decays B̅ 0→χc1K-π+ and B+→χc1KS0π+ where χc1→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 χc1π+ 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 χc1π+ mass distribution. No evidence is found for the Z1(4050)+ and Z2(4250)+ resonances, and 90% confidence level upper limits on the branching fractions are reported for the corresponding B-meson decay modes.
  Phys. Rev. D. 03/2012; 85(5).
• Source

  Available from: Marco Bomben

  Article: Initial-State Radiation Measurement of the e+e- -> pi+pi-pi+pi- Cross Section

  J. P. Lees, V. Poireau, V. Tisserand, J. Garra Tico, E. Grauges, M. Martinelli, D. A. Milanes, A. Palano, M. Pappagallo, G. Eigen, [......], N. Tasneem, T. J. Gershon, P. F. Harrison, T. E. Latham, E. M. T. Puccio, H. R. Band, S. Dasu, Y. Pan, R. Prepost, S. L. Wu
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  ABSTRACT: We study the process e+e- -> pi+pi-pi+pi-gamma, with a photon emitted from the initial-state electron or positron, using 454.3 fb^-1 of data collected with the BABAR detector at SLAC, corresponding to approximately 260,000 signal events. We use these data to extract the non-radiative sigma(e+e- ->pi+pi-pi+pi-) cross section in the energy range from 0.6 to 4.5 Gev. The total uncertainty of the cross section measurement in the peak region is less than 3%, higher in precision than the corresponding results obtained from energy scan data.
  01/2012;
• Article: Branching fraction measurements of the color-suppressed decays B̅ 0 to D(*)0π0, D(*)0η, D(*)0ω, and D(*)0η′ and measurement of the polarization in the decay B̅ 0→D*0ω

  J. P. Lees, V. Poireau, V. Tisserand, J. Garra Tico, E. Grauges, M. Martinelli, D. A. Milanes, A. Palano, M. Pappagallo, G. Eigen, [......], N. Tasneem, T. J. Gershon, P. F. Harrison, T. E. Latham, E. M. T. Puccio, H. R. Band, S. Dasu, Y. Pan, R. Prepost, S. L. Wu
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  ABSTRACT: We report updated branching fraction measurements of the color-suppressed decays B̅ 0→D0π0, D*0π0, D0η, D*0η, D0ω, D*0ω, D0η′, and D*0η′. We measure the branching fractions (×10-4): B(B̅ 0→D0π0)=2.69±0.09±0.13, B(B̅ 0→D*0π0)=3.05±0.14±0.28, B(B̅ 0→D0η)=2.53±0.09±0.11, B(B̅ 0→D*0η)=2.69±0.14±0.23, B(B̅ 0→D0ω)=2.57±0.11±0.14, B(B̅ 0→D*0ω)=4.55±0.24±0.39, B(B̅ 0→D0η′)=1.48±0.13±0.07, and B(B̅ 0→D*0η′)=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)×106 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.
  Phys. Rev. D. 12/2011; 84(11).
• Article: Branching fraction measurements of the color-suppressed decays B̅ 0 to D(*)0π0, D(*)0η, D(*)0ω, and D(*)0η′ and measurement of the polarization in the decay B̅ 0→D*0ω

  J. P. Lees, V. Poireau, V. Tisserand, J. Garra Tico, E. Grauges, M. Martinelli, D. A. Milanes, A. Palano, M. Pappagallo, G. Eigen, [......], N. Tasneem, T. J. Gershon, P. F. Harrison, T. E. Latham, E. M. T. Puccio, H. R. Band, S. Dasu, Y. Pan, R. Prepost, S. L. Wu
  [show abstract] [hide abstract]
  ABSTRACT: We report updated branching fraction measurements of the color-suppressed decays B̅ 0→D0π0, D*0π0, D0η, D*0η, D0ω, D*0ω, D0η′, and D*0η′. We measure the branching fractions (×10-4): B(B̅ 0→D0π0)=2.69±0.09±0.13, B(B̅ 0→D*0π0)=3.05±0.14±0.28, B(B̅ 0→D0η)=2.53±0.09±0.11, B(B̅ 0→D*0η)=2.69±0.14±0.23, B(B̅ 0→D0ω)=2.57±0.11±0.14, B(B̅ 0→D*0ω)=4.55±0.24±0.39, B(B̅ 0→D0η′)=1.48±0.13±0.07, and B(B̅ 0→D*0η′)=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)×106 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.
  Phys. Rev. D. 12/2011; 84(11).
• Article: Observation of the rare decay B+→K+π0π0 and measurement of the quasi-two-body contributions B+→K*(892)+π0, B+→f0(980)K+, and B+→χc0K+

  J. P. Lees, V. Poireau, V. Tisserand, J. Garra Tico, E. Grauges, M. Martinelli, D. A. Milanes, A. Palano, M. Pappagallo, G. Eigen, [......], N. Tasneem, T. J. Gershon, P. F. Harrison, T. E. Latham, E. M. T. Puccio, H. R. Band, S. Dasu, Y. Pan, R. Prepost, S. L. Wu
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  ABSTRACT: We report an analysis of charmless hadronic decays of charged B mesons to the final state K+π0π0, using a data sample of (470.9±2.8)×106 BB̅ events collected with the BABAR detector at the Υ(4S) resonance. We observe an excess of signal events, with a significance above 10 standard deviations including systematic uncertainties, and measure the branching fraction and CP asymmetry to be B(B+→K+π0π0)=(16.2±1.2±1.5)×10-6 and ACP(B+→K+π0π0)=-0.06±0.06±0.04, where the uncertainties are statistical and systematic, respectively. Additionally, we study the contributions of the B+→K*(892)+π0, B+→f0(980)K+, and B+→χc0K+ quasi-two-body decays. We report the world’s best measurements of the branching fraction and CP asymmetry of the B+→K+π0π0 and B+→K*(892)+π0 channels.
  Phys. Rev. D. 11/2011; 84(9).
• Article: Search for hadronic decays of a light Higgs boson in the radiative decay Υ→γA0.

  J P Lees, V Poireau, V Tisserand, J Garra Tico, E Grauges, M Martinelli, D A Milanes, A Palano, M Pappagallo, G Eigen, [......], N Tasneem, T J Gershon, P F Harrison, T E Latham, E M T Puccio, H R Band, S Dasu, Y Pan, R Prepost, S L Wu
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  ABSTRACT: We search for hadronic decays of a light Higgs boson (A(0)) produced in radiative decays of an Υ(2S) or Υ(3S) meson, Υ→γA(0). The data have been recorded by the BABAR experiment at the Υ(3S) and Υ(2S) center-of-mass energies and include (121.3±1.2)×10(6) Υ(3S) and (98.3±0.9)×10(6) Υ(2S) mesons. No significant signal is observed. We set 90% confidence level upper limits on the product branching fractions B(Υ(nS)→γA(0))B(A(0)→hadrons) (n=2 or 3) that range from 1×10(-6) for an A(0) mass of 0.3 GeV/c(2) to 8×10(-5) at 7 GeV/c(2).
  Physical Review Letters 11/2011; 107(22):221803. · 7.37 Impact Factor
• Article: Study of Υ(3S,2S)→ηΥ(1S) and Υ(3S,2S)→π+π-Υ(1S) hadronic transitions

  J. P. Lees, V. Poireau, V. Tisserand, J. Garra Tico, E. Grauges, M. Martinelli, D. A. Milanes, A. Palano, M. Pappagallo, G. Eigen, [......], N. Tasneem, T. J. Gershon, P. F. Harrison, T. E. Latham, E. M. T. Puccio, H. R. Band, S. Dasu, Y. Pan, R. Prepost, S. L. Wu
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  ABSTRACT: We study the Υ(3S,2S)→ηΥ(1S) and Υ(3S,2S)→π+π-Υ(1S) transitions with 122×106Υ(3S) and 100×106Υ(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/c2 and 893.813±0.015(stat.)±0.107(syst.) MeV/c2, respectively.
  Phys. Rev. D. 11/2011; 84(9).
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  Available from: Marco Bomben

  Article: A Measurement of the Semileptonic Branching Fraction of the B_s Meson

  The BaBar Collaboration, J. P. Lees, V. Poireau, V. Tisserand, J. Garra Tico, E. Grauges, M. Martinelli, D. A. Milanes, A. Palano, M. Pappagallo, [......], N. Tasneem, T. J. Gershon, P. F. Harrison, T. E. Latham, E. M. T. Puccio, H. R. Band, S. Dasu, Y. Pan, R. Prepost, S. L. Wu
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  ABSTRACT: We report a measurement of the inclusive semileptonic branching fraction of the B_s meson using data collected with the BaBar detector in the center-of-mass (CM) energy region above the Upsilon(4S) resonance. We use the inclusive yield of phi mesons and the phi yield in association with a high-momentum lepton to perform a simultaneous measurement of the semileptonic branching fraction and the production rate of B_s mesons relative to all B mesons as a function of CM energy. The inclusive semileptonic branching fraction of the B_s meson is determined to be B(B_s to l nu X)=9.5 (+2.5/-2.0)(stat)(+1.1/-1.9)(syst)%, where l indicates the average of e and mu.
  10/2011;
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  Available from: Marco Bomben

  Article: Search for hadronic decays of a light Higgs boson in the radiative decay Upsilon --> gamma A0

  The BABAR Collaboration, J P Lees, V Poireau, V Tisserand, J Garra Tico, E Grauges, M Martinelli, D. A. Milanes, A Palano, M Pappagallo, [......], N. Tasneem, T. J. Gershon, P F Harrison, T E Latham, E. M. T. Puccio, H R Band, S Dasu, Y Pan, R Prepost, S L Wu
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  ABSTRACT: We search for hadronic decays of a light Higgs boson (A0) produced in radiative decays of an Upsilon(2S) or Upsilon(3S) meson, Upsilon --> gamma A0. The data have been recorded by the BABAR experiment at the Upsilon(3S) and Upsilon(2S) center of mass energies, and include (121.3 \pm 1.2) x 10^6 Upsilon(3S) and (98.3 \pm 0.9) x 10^6 Upsilon(2S) mesons. No significant signal is observed. We set 90% confidence level upper limits on the product branching fractions B(Upsilon(nS)-->gamma A0) x B(A0-->hadrons) (n=2 or 3) that range from 1 x 10^{-6} for an A0 mass of 0.3 GeV/c^2 to 8 x 10^{-5} at 7 GeV/c^2.
  08/2011;
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  Available from: Marco Bomben

  Article: Observation of the baryonic B decay B0bar --> Lambda_c^+ anti-Lambda K-

  The BABAR Collaboration, J P Lees, V Poireau, V Tisserand, J Garra Tico, E Grauges, M Martinelli, D. A. Milanes, A Palano, M Pappagallo, [......], T. J. Gershon, P F Harrison, T E Latham, E. M. T. Puccio, H R Band, S Dasu, Y Pan, R Prepost, C. O. Vuosalo, S L Wu
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  ABSTRACT: We report the observation of the baryonic B decay B0bar --> Lambda_c^+ anti-Lambda K- with a significance larger than 7 standard deviations based on 471x10^6$ BBbar pairs collected with the BABAR detector at the PEP-II storage ring at SLAC. We measure the branching fraction for the decay B0bar --> Lambda_c^+ anti-Lambda K- to be (3.8 \pm 0.8_{stat} \pm 0.2_{sys} \pm 1.0_{Lambda_c^+})x10^{-5}. The uncertainties are statistical, systematic, and due to the uncertainty in the Lambda_c^+ branching fraction. We find that the Lambda_c^+ K^- invariant mass distribution shows an enhancement above 3.5 GeV/c^2.
  08/2011;
• Article: Observation of the decay B- → D(s)((*)+) K- ℓ- ν(ℓ).

  P del Amo Sanchez, J P Lees, V Poireau, E Prencipe, V Tisserand, J Garra Tico, E Grauges, M Martinelli, A Palano, M Pappagallo, [......], P F Harrison, T E Latham, E M T Puccio, H R Band, S Dasu, K T Flood, Y Pan, R Prepost, C O Vuosalo, S L Wu
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  ABSTRACT: We report the observation of the decay B- → D(s)((*)+) K- ℓ- ν(ℓ) based on 342  fb(-1) of data collected at the Υ(4S) resonance with the BABAR detector at the PEP-II e+ e- storage rings at SLAC. A simultaneous fit to three D(s)(+) decay chains is performed to extract the signal yield from measurements of the squared missing mass in the B meson decay. We observe the decay B- → D(s)((*)+) K- ℓ- ν(ℓ) with a significance greater than 5 standard deviations (including systematic uncertainties) and measure its branching fraction to be B(B- → D(s)((*)+) K- ℓ- ν(ℓ)) = [6.13(-1.03)(+1.04)(stat)±0.43(syst)±0.51(B(D(s)))]×10(-4), where the last error reflects the limited knowledge of the D(s) branching fractions.
  Physical Review Letters 07/2011; 107(4):041804. · 7.37 Impact Factor
• Article: Observation of ηc(1S) and ηc(2S) decays to K+K-π+π-π0 in two-photon interactions

  P. del Amo Sanchez, J. P. Lees, V. Poireau, E. Prencipe, V. Tisserand, J. Garra Tico, E. Grauges, M. Martinelli, A. Palano, M. Pappagallo, [......], P. F. Harrison, T. E. Latham, E. M. T. Puccio, H. R. Band, S. Dasu, K. T. Flood, Y. Pan, R. Prepost, C. O. Vuosalo, S. L. Wu
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  ABSTRACT: We study the processes γγ→KS0K±π∓ and γγ→K+K-π+π-π0 using a data sample of 519.2fb-1 recorded by the BABAR detector at the PEP-II asymmetric-energy e+e- collider at center-of-mass energies near the Υ(nS) (n=2, 3, 4) resonances. We observe the ηc(1S), χc0(1P) and ηc(2S) resonances produced in two-photon interactions and decaying to K+K-π+π-π0, with significances of 18.1, 5.4 and 5.3 standard deviations (including systematic errors), respectively, and report 4.0σ evidence of the χc2(1P) decay to this final state. We measure the ηc(2S) mass and width in KS0K±π∓ decays, and obtain the values m(ηc(2S))=3638.5±1.5±0.8 MeV/c2 and Γ(ηc(2S))=13.4±4.6±3.2 MeV, where the first uncertainty is statistical and the second is systematic. We measure the two-photon width times branching fraction for the reported resonance signals, and search for the χc2(2P) resonance, but no significant signal is observed.
  Phys. Rev. D. 07/2011; 84(1).
• Article: Search for production of invisible final states in single-photon decays of Υ(1S).

  P del Amo Sanchez, J P Lees, V Poireau, E Prencipe, V Tisserand, J Garra Tico, E Grauges, M Martinelli, D A Milanes, A Palano, [......], P F Harrison, T E Latham, E M T Puccio, H R Band, S Dasu, K T Flood, Y Pan, R Prepost, C O Vuosalo, S L Wu
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  ABSTRACT: We search for single-photon decays of the Υ(1S) resonance, Υ → γ + invisible, where the invisible state is either a particle of definite mass, such as a light Higgs boson A⁰, or a pair of dark matter particles, χχ. Both A⁰ and χ are assumed to have zero spin. We tag Υ(1S) decays with a dipion transition Υ(2S) → π⁺π⁻Υ(1S) and look for events with a single energetic photon and significant missing energy. We find no evidence for such processes in the mass range m(A⁰) ≤ 9.2 GeV and m(χ) ≤ 4.5 GeV in the sample of 98 × 10⁶ Υ(2S) decays collected with the BABAR detector and set stringent limits on new physics models that contain light dark matter states.
  Physical Review Letters 07/2011; 107(2):021804. · 7.37 Impact Factor