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B. Aubert

Publications and source records attributed to B. Aubert.

At least 73 records · Page 4Linked to original sources

Evidence for B+ -> K*0bar K*+

We present measurements of the branching fraction and fraction of longitudinal polarization for the decay B+ -> K*0bar K*+ with a sample of 467 +/- 5 million BBbar pairs collected with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at the SLAC National Accelerator Laboratory. We obtain the branching fraction Br(B+ -> K*0bar K*+) = (1.2 +/- 0.5 +/- 0.1) x 10^{-6} with a significance of 3.7 standard deviations including systematic uncertainties. We measure the fraction of longitudinal polarization f_L = 0.75+0.16-0.26 +/- 0.03. The first error quoted is statistical and the second is systematic.

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Angular Distributions in the Decays B -> K* l+l-

We use a sample of 384 million BBbar events collected with the Babar detector at the PEP-II e+e- collider to study angular distributions in the rare decays B -> K* l+l-, where l+l- is either e+e- or mu+mu-. For low dilepton invariant masses, m(l+l-)<2.5 GeV/c^2, we measure a lepton forward-backward asymmetry AFB=0.24 (+0.18,-0.23) +/- 0.05 and K* longitudinal polarization FL=0.35 +/- 0.16 +/- 0.04$. For m(l+l-)>3.2$ GeV/c^2, we measure AFB=0.76 (+0.52,-0.32) +/- 0.07 FL=0.71 (+0.20,-0.22) +/- 0.04.

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Measurements of ${\cal B}(\bar{B}^0 \to Λ_{c}^{+} \bar{p})$ and ${\cal B}(B^- \to Λ_{c}^{+} \bar{p} π^-)$ and Studies of $Λ_{c}^{+}π^-$ Resonances

We present an investigation of the decays $\bar{B}^0 \to Λ_{c}^{+} \bar{p}$ and $B^- \to Λ_{c}^{+} \bar{p} π^-$ based on $383\times10^6$ $Υ(4S) \to B\bar{B}$ decays recorded with the BABAR detector. We measure the branching fractions of these decays; their ratio is ${\cal B}(B^- \to Λ_{c}^{+} \bar{p} π^-) / {\cal B}(\bar{B}^0 \to Λ_{c}^{+} \bar{p}) = 15.4 \pm 1.8 \pm 0.3$. The $B^- \to Λ_{c}^{+} \bar{p} π^-$ process exhibits an enhancement at the $Λ_{c}^{+} \bar{p}$ threshold and is a laboratory for searches for excited charm baryon states. We observe the resonant decays $\bar{B}^- \to Σ_{c}(2455)^{0} \bar{p}$ and $B^- \to Σ_{c}(2800)^{0} \bar{p}$ but see no evidence for $B^- \to Σ_{c}(2520)^{0} \baver{p}$. This is the first observation of the decay $B^- \to Σ_{c}(2800)^{0} \bar{p}$; however, the mass of the observed excited $Σ_{c}^{0}$ state is $(2846\pm8\pm10)MeV/c^2$, which is somewhat inconsistent with previous measurements. Finally, we examine the angular distribution of the $B^- \to Σ_{c}(2455)^{0} \bar{p}$ decays and measure the spin of the $Σ_{c}(2455)^{0}$ baryon to be 1/2, as predicted by the quark model.

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Measurement of time dependent CP asymmetry parameters in B0 meson decays to omega K0S, eta'K0, and pi0K0S

We present measurements of the time-dependent CP-violation parameters S and C in the decays omega K0S, eta'K0, reconstructed as eta'K0S and eta'K0L, and pi0K0S. The data sample corresponds to the full BABAR dataset of 467 x 10^6 BB pairs produced at the PEP-II asymmetric-energy e+e- collider at the Stanford Linear Accelerator Center. The results are S_{omega K0S} = 0.55^{+0.26}_{-0.29} +/- 0.02, C_{omega K0S} = -0.52^{+0.22}_{-0.20} +/- 0.03, S_{eta' K0} = 0.57 +/- 0.08 +/- 0.02, C_{eta' K0} = -0.08 +/- 0.06 +/- 0.02, S_{pi0 K0S} = 0.55 +/- 0.20 +/- 0.03, and C_{pi0 K0S} = 0.13 +/- 0.13 +/- 0.03, where the first errors are statistical and the second systematic. These results are consistent with our previous measurements and the world average of sin2beta measured in B0 -> J/psi K0S.

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Study of hadronic transitions between Y states and observation of Y(4S)-> eta Y(1S) decay

We present a study of hadronic transitions between Y(mS) (m=4,3,2) and Y(nS) (n=2,1) resonances based on 347.5\invfb of data taken with the BABAR detector at the PEP-II storage rings. We report the first observation of Y(4S)-> eta Y(1S) decay with a branching fraction BR((Y(4S)->eta Y(1S))=(1.96+-0.06_{stat} +-0.09_{syst}) x 10^{-4} and measure the ratio of partial widths Gamma(Y(4S)->etaY(1S))/Gamma(Y(4S)->pi+pi-Y(1S))=2.41+- 0.40_{stat}+- 0.12_{syst}. We set 90% CL upper limits on the ratios Gamma(Y(2S)->etaY(1S))/Gamma(Y(2S)->pi+pi-Y(1S))<5.2 x10^{-3}$ and Gamma(Y(3S)->etaY(1S))/Gamma(Y(3S)->pi+pi-Y(1S))<1.9x10^{-2}. We also present new measurements of the ratios Gamma(Y(4S)->pi+pi-Y(2S))/Gamma(Y(4S)->pi+pi-Y(1S))=1.16+- 0.16_{stat}+- 0.14_{syst} and Gamma(Y(3S)->pi+pi-Y(2S))/Gamma(Y(3S)->pi+pi-Y(1S))=0.577+- 0.026_{stat}+- 0.060_{syst}.

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Search for Lepton Flavour Violating Decays $τ\to \ell K^0_S$ with the BaBar Experiment

A search for the lepton flavour violating decays $τ^- \to l^- K^0_{\scriptscriptstyle S}$ ($l = e$ or $μ$) has been performed using a data sample corresponding to an integrated luminosity of 469 ${fb}^{-1}$, collected with the {\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}} detector at the SLAC PEP-II $e^+e^-$ asymmetric energy collider. No statistically significant signal has been observed in either channel and the estimated upper limits on branching fractions are ${\cal B}(τ^- \to e^- K^0_{\scriptscriptstyle S}) < 3.3 \times 10^{-8}$ and ${\cal B}(τ^- \to μ^- K^0_{\scriptscriptstyle S}) < 4.0 \times 10^{-8}$ at 90% confidence level.

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Measurements of the Semileptonic Decays $\Bb\to D\ell\nub$ and $\Bb\to D^*\ell\nub$ Using a Global Fit to $D X\ell\nub$ Final States

Semileptonic $\bar{B}$ decays to $DX\ell\barν$ ($\ell=e$ or $mu$) are selected by reconstructing $D0\ell$ and $D^+\ell$ combinations from a sample of 230 million $Υ(4S) \to B\bar{B}$ decays recorded with the BaBar detector at the PEPII $e^+e^-$ collider at SLAC. A global fit to these samples in a 3-dimensional space of kinematic variables is used to determine the branching fractions $\mathcal{B}(B^- \to D0\ell\barν) = (2.34 \pm 0.03 \pm 0.13) %$ and $\mathcal{B}(B^- \to D^{*0}\ell\barν) = (5.40 \pm 0.02 \pm 0.21) %$,where the errors are statistical and systematic, respectively. The fit also determines form factor parameters in a HQET-based parameterization, resulting in $ρ_D2 = 1.20 \pm 0.04 \pm 0.07$ for $\bar{B} \to D\ell\barν$ and $ρ_{D^*}2 = 1.22 \pm 0.02 \pm 0.07$ for $\bar{B} \to D^*\ell\barν$ These values are used to obtain the product of the CKM matrix element $|V_{cb}|$ times the form factor at the zero recoil point for both $\bar{B} \to D\ell\barν$ decays, $\mathcal{G}(1)|V_{cb}| = (43.1 \pm 0.8 \pm 2.3)\times 10^{-3}$, and for $\bar{B} \to D^*\ell\barν$ decays, $\mathcal{F}(1)|V_{cb}| = (35.9 \pm 0.2 \pm 1.2)\times 10^{-3}$.

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A Measurement of CP Asymmetry in b->sgamma using a Sum of Exclusive Final States

We perform a measurement of the CP asymmetry in b->sgamma decays using a sample of 383 BB events collected by the BABAR detector at the PEP-II asymmetric B factory. We reconstruct sixteen flavor-specific B decay modes containing a high-energy photon and a hadronic system (Xs) containing an s quark. We measure the \CP asymmetry to be -0.011+/- 0.030(stat)+/-0.014(syst) for a photon energy threshold at 1.6 GeV and the hadronic system mass between 0.6 and 2.8 GeV/c2.

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Search for the Lepton-Flavor Violating Decays Upsilon(3S) -> e tau and Upsilon(3S) -> mu tau

Charged lepton-flavor violating processes are extremely rare in the Standard Model, but they may occur in several beyond-the-Standard Model theories, including Supersymmetry or models with leptoquarks or compositeness. We present a search for such processes in a sample of 117M Upsilon(3S) decays recorded with the BaBar detector. We place upper limits on the branching fractions BF(Upsilon(3S) -> e tau) < 5.0e-6 and BF(Upilon(3S) -> mu tau) < 4.1e-6 at 90% confidence level. These results are used to place lower limits on the mass scale of beyond-the-Standard Model physics contributing to lepton-flavor violating decays of the Upsilon(3S).

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Observation of the bottomonium ground state in the decay Upsilon(3S) -> gamma eta_b

We report the results of a search for the bottomonium ground state eta_b(1S) in the photon energy spectrum with a sample of (109 +/- 1) million of Upsilon(3S) recorded at the Upsilon(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_gamma = 921.2 {+2.1} {-2.8} (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 Upsilon(3S) -> gamma eta_b(1S). This photon energy corresponds to an eta_b(1S) mass of $9388.9 {+3.1} {-2.3} (stat) +/- 2.7(syst) MeV/c2. The hyperfine Upsilon(1S)-eta_b(1S) mass splitting is 71.4 {+2.3} {-3.1} (stat) +/- 2.7(syst) MeV/c2. The branching fraction for this radiative Upsilon(3S) decay is estimated to be (4.8 +/- 0.5(stat) +/- 1.2 (syst)) x 10^(-4).

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Search for B0 -> K*+ K*-

We report the results of a search for the decay B0 -> K*+ K*- with a sample of 454 +/- 5 million BBbar 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 Br(B0 -> K*+ K*-) < 2.0 x 10^{-6}, assuming the decay is fully longitudinally polarized.

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Search for the highly suppressed decays B- -> K+ pi- pi- and B- -> K- K- pi+

We report a search for the decays B- -> K+ pi- pi- and B- -> K- K- pi+, which are highly suppressed in the Standard Model. Using a sample of (467 +/- 5) x 10^6 BBbar pairs collected with the BaBar detector, we do not see any evidence of these decays and determine 90% confidence level upper limits of BF(B- -> K+ pi- pi-) < 9.5 x 10^-7 and BF(B- -> K- K- pi+) < 1.6 x 10^-7 on the corresponding branching fractions, including systematic uncertainties.

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Observation of B0 -> chi_c0K*0 and evidence for B+ -> chi_c0K*+

We present the observation of the decay B0 -> chi_c0K*0 as well as evidence of B+ -> chi_c0K*+, with an 8.9 and a 3.6 standard deviation significance, respectively, using a data sample of 454 million Y(4S) -> BB 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 -> chi_c0K*0) = (1.7 +/- 0.3 +/- 0.2) * 10^{-4} and B(B+ -> chi_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+ -> chi_c0K*+) < 2.1 * 10^{-4} at the 90% confidence level.

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Search for the Z(4430)^- at BABAR

We report the results of a search for $Z(4430)^-$ decay to $J/ψπ^-$ or $ψ(2S)π^-$ in $B^{-,0}\to \jpsiπ^- K^{0,+}$ and $B^{-,0}\to \psitwos π^- K^{0,+}$ decays. 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 the sample corresponds to an integrated luminosity of 413 fb$^{-1}$. Each $Kπ$ mass distribution exhibits clear $K^{\ast}(892)$ and $K^{\ast}_2(1430)$ signals, and the efficiency-corrected spectrum is well-described by a superposition of the associated Breit-Wigner intensity distributions, together with an $S$-wave contribution obtained from the LASS $I=1/2$ $Kπ$ scattering amplitude measurements. Each $Kπ$ angular distribution varies significantly in structure with $Kπ$ mass, and is represented in terms of low-order Legendre polynomial moments. We find that each $J/ψπ$ or $ψ(2S)π$ mass distribution is well-described by the reflection of the measured $Kπ$ mass and angular distribution structures. We see no significant evidence for a $Z(4430)^-$ signal for any of the processes investigated, neither in the total $J/ψπ$ or $ψ(2S)π$ mass distribution, nor in the corresponding distributions for the regions of $Kπ$ mass for which observation of the $Z(4430)^-$ signal was reported. We obtain branching fraction upper limits ${\cal{B}}(B^-\to Z^-\bar{K^0}, Z^-\to J/ψπ^-)<1.5\times 10^{-5}$, ${\cal{B}}(B^0\to Z^-K^+, Z^-\to J/ψπ^-)<0.4\times 10^{-5}$, ${\cal{B}}(B^-\to Z^-\bar{K^0}, Z^-\to ψ(2S)π^-)<4.7\times 10^{-5}$, and ${\cal{B}}(B^0\to Z^-K^+, Z^-\to ψ(2S)π^-)<3.1\times 10^{-5}$ at 95% confidence level, where the $Z(4430)^-$ mass and width have been fixed to the reported central values.

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Search for B --> K* nu anti-nu decays

We present a search for the decays $B \to K^{*} ν\barν$ using 454$\times10^{6}$ $B \bar{B}$ pairs collected at the $Υ(4S)$ resonance with the $mbox{\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}}$ 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 $B \to K^{*} ν\barν$ decay. The charged $K^{*}$ is reconstructed as $ K^{*+} \to K^0_{\scriptscriptstyle S} π^{+}$ or $ K^{*+} \to K^{+} π^{0}$; the neutral $K^{*}$ is identified in the $K^{*0} \to K^{+} π^{-}$ mode. We establish upper limits at 90% confidence level of $\matchal{B}(B^{+} \to K^{*+} ν\barν) < 8 \times 10^{-5}$, $\matchal{B}(B^{0} \to K^{*0} ν\barν) < 12 \times 10^{-5}$, and $\matchal{B}(B \to K^{*} ν\barν) < 8 \times 10^{-5}$.

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Observation and Polarization Measurements of B+- ->phi K_1+- and B+- ->phi K_2*+-

With the full $\babar$ data sample of 465 million BaBar pairs, we observe the decays B+- ->phi(1020) K_1(1270)+- and B+- ->phi(1020) K_2*(1430) +-. We measure the branching fractions (6.1+-1.6+-1.1)\times 10^{-6} and (8.4+- 1.9+- 0.9)\times 10^{-6} and the fractions of longitudinal polarization 0.46(+0.12-0.13)(+0.03-0.07) and 0.80(+0.09-0.10)+-0.03, respectively. We also report on the B+- ->phi K_0*(1430)+- decay branching fraction of (7.0+-1.3+-0.9)\times10^{-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 phi and K_1(1400)+-, K*(1410)+-, K_2(1770)+-,or K_2(1820)+-. Understanding the observed polarization pattern requires amplitude contributions from an uncertain source.

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Measurement of Time-Dependent CP Asymmetry in B0 --> KS pi0 gamma Decays

We measure the time-dependent CP asymmetry in B0 --> K_S0 pi0 gamma decays for two regions of K_S0-pi0 invariant mass, m(K_S0 pi0), using the final BABAR data set of 467 x 10^6 BBbar pairs collected at the PEP-II e+e- collider at SLAC. We find 339 +/- 24 B0 --> K*0 gamma candidates and measure S_{K* gamma} = -0.03 +/- 0.29 +/- 0.03 and C_{K* gamma} = -0.14 +/- 0.16 +/- 0.03. In the range 1.1 < m(K_S0 pi0) < 1.8 GeV/c^2 we find 133 +/- 20 B0 --> K_S0 pi0 gamma candidates and measure S_{K_S0 pi0 gamma} = -0.78 +/- 0.59 +/- 0.09 and C_{K_S0 pi0 gamma} = -0.36 +/- 0.33 +/- 0.04. The uncertainties are statistical and systematic, respectively.

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Searches for B meson decays to phiphi, phirho, phifzero(980), and fzero(980)fzero(980) final states

We present the results of searches for B decays to charmless final states involving phi, fzero(980), and charged or neutral rho mesons. The data sample corresponds to 384 million BBbar pairs collected with the babar detector operating at the PEP-II asymmetric-energy epem 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->phiphi) < 2.0 x 10^-7, B(B+->phirho+) < 30 x 10^-7, B(B0->phirho0) < 3.3 x 10^-7, B(B0-phif0) x B(f0->pi+pi-) < 3.8 x 10^-7, and B(B0->f0f0) x B(f0->pi+pi-) x B(f0->K+K-) < 2.3 x 10^-7

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