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B. Aubert

Publications and source records attributed to B. Aubert.

At least 127 records · Page 7Linked to original sources

Measurements of the Branching Fractions of B0 --> K^*0K+K-, B0 --> K^*0pi+K-, B0 --> K*0K+pi-, and B0 --> K*0pi+pi-

Branching fraction and asymmetry measurements of charmless $B^0\to K^{*0}h^+_1h^-_2$ ($h_{1,2}$ = $K$, $π$) decays are presented, using a data sample of 383 million $Υ(4S) \to$ $B\bar{B$} decays collected with the BaBar detector at the PEP-II asymmetric-energy $B$-meson factory at SLAC. The results are: ${\cal B}$($B^0 \to K^{*0}K^+ K^-)$ = (27.5 $\pm$ 1.3 $\pm$ 2.2) $\times$ 10$^{-6}$, ${\cal B}$($B^0$ $\to$ $K^{*0}π^+ K^-$) = (4.6 $\pm$ 1.1 $\pm$ 0.8) $\times$ 10$^{-6}$ and ${\cal B}$($B^0$ $\to$ $K^{*0}π^+π^-$) = (54.5 $\pm$ 2.9 $\pm$ 4.3) $\times$ 10$^{-6}$. The first errors quoted are statistical and the second are systematic. An upper limit is set for ${\cal B}$($B^0$ $\to$ $K^{*0}K^+ π^-$) $<$ 2.2 $\times$ 10$^{-6}$ at 90% confidence level. We also present measurements of CP-violating asymmetries for the observed decays.

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The $e^+ e^-\to 2(π^+π^-)π^0$, 2(π^+π^-)η$, $K^+ K^-π^+π^-π^0$ and $K^+ K^-π^+π^-η$ Cross Sections Measured with Initial-State Radiation

We study the processes $e^+ e^-\to 2(π^+π^-)π^0γ$, $2(π^+π^-)ηγ$, $K^+ K^-π^+π^-π^0γ$ and $K^+ K^-π^+π^-ηγ$ with the hard photon radiated from the initial state. About 20000, 4300, 5500 and 375 fully reconstructed events, respectively, are selected from 232 fb$^{-1}$ of BaBar data. The invariant mass of the hadronic final state defines the effective $e^+ e^-$ center-of-mass energy, so that the obtained cross sections from the threshold to about 5 GeV can be compared with corresponding direct \epem measurements, currently available only for the $ηπ^+π^-$ and $ωπ^+π^-$ submodes of the $e^+ e^-\to 2(π^+π^-)π^0$ channel. Studying the structure of these events, we find contributions from a number of intermediate states, and we extract their cross sections where possible. In particular, we isolate the contribution from $e^+ e^-\toω(782)π^+π^-$ and study the $ω(1420)$ and $ω(1650)$ resonances. In the charmonium region, we observe the $J/ψ$ in all these final states and several intermediate states, as well as the $ψ(2S)$ in some modes, and we measure the corresponding branching fractions.

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Measurements of B --> {pi, eta, eta'} l nu Branching Fractions and Determination of |Vub| with Semileptonically Tagged B Mesons

We report measurements of branching fractions for the decays B --> P l nu, where P are the pseudoscalar charmless mesons pi-, pi0, eta and eta', 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(*) l nu. Assuming isospin symmetry, we combine pionic branching fractions to obtain B(B0 --> pi- l+ nu) = (1.54 +/- 0.17(stat) +/- 0.09(syst)) x 10-4; we find 3.2 sigma evidence of the decay B+ --> eta l+ nu and measure its branching fraction to be (0.64 +/- 0.20 (stat) +/- 0.03 (syst)) x 10-4, and determine B(B+ --> eta' l+ nu) < 0.47 x 10-4 to 90% confidence level. Using partial branching fractions for the pionic decays in ranges of the momentum transfer and a recent form factor calculation, we obtain the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element |Vub| = (4.0 +/- 0.5(stat) +/- 0.2(syst) +0.7-0.5(theory)) x 10-3.

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Branching Fractions and CP-Violating Asymmetries in Radiative B Decays to eta K gamma

We present measurements of the CP-violation parameters S and C for the radiative decay B0 -> eta K0s gamma; for B -> eta K gamma we also measure the branching fractions and for B+ -> eta K+ gamma the time-integrated charge asymmetry Ach. The data, collected with the BaBar detector at the Stanford Linear Accelerator Center, represent $465 \times 10^6$ BBbar pairs produced in $e^{+} e^{-}$ annihilation. The results are $S = -0.18^{+0.49}_{-0.46} \pm 0.12$, $C = -0.32^{+0.40}_{-0.39} \pm 0.07$, BF(B0 -> eta K0 gamma) = $(7.1^{+2.1}_{-2.0} \pm 0.4) \times 10^{-6}$, BF(B+ -> eta K+ gamma) = $(7.7+-1.0 \pm 0.4) \times 10^{-6}$, and Ach = $(-9.0^{+10.4}_{-9.8} \pm 1.4) \times 10^{-2}$. The first error quoted is statistical and the second systematic.

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Observation of B+->b_1+K0 and search for B-meson decays to b_10K0 and b_1pi0

We present the results of searches for decays of B mesons to final states with a b_1 meson and a neutral pion or kaon. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 465 million BBbar pairs produced in e+e- annihilation. The results for the branching fractions are, in units of 1e-6, BR(B+ to b_1+K0) = 9.6+/-1.7+/-0.9, BR(B0 to b_10K0) = 5.1+/-1.8+/-0.5 (<7.8), BR(B+ to b_1+pi0) = 1.8+/-0.9+/-0.2 (<3.3), and BR(B0 to b_10pi0) = 0.4+/-0.8+/-0.2 (<1.9), with the assumption that BR(B_1 to omega pi)=1. We also measure the charge asymmetry A_ch(B+ to b_1+K0) = -0.03+/-0.15+/-0.02. The first error quoted is statistical, the second systematic, and the upper limits in parentheses indicate the 90% confidence level.

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Measurement of branching fractions and mass spectra of B -> K pi pi gamma

We present a measurement of the partial branching fractions and mass spectra of the exclusive radiative penguin processes B -> K pi pi gamma in the range m_Kpipi < 1.8 GeV/c^2. We reconstruct four final states: K+ pi- pi+ gamma, K+ pi- pi0 gamma, Ks pi- pi+ gamma, and Ks pi+ pi- gamma, where Ks -> pi+ pi-. Using 232 million e+ e- -> B Bbar events recorded by the BaBar experiment at the PEP-II asymmetric-energy storage ring, we measure the branching fractions BR(B+ -> K+ pi- pi+ gamma) = (2.95 +- 0.13 (stat.) +- 0.20 (syst.)) x 10^-5, BR(B0 -> K+ pi- pi0 gamma) = (4.07 +- 0.22 (stat.) +- 0.31 (syst.)) x 10^-5, BR(B0 -> K0 pi+ pi- gamma) = (1.85 +- 0.21 (stat.) +- 0.12 (syst.)) x 10^-5, and BR(B+ -> K0 pi+ pi0 gamma) = (4.56 +- 0.42 (stat.) +- 0.31 (syst.)) x 10^-5.

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Observation of B->etarho+ and search for B0 Decays to eta'eta, etapi0, eta'pi0, and omegapi0

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 million BBbar pairs. The results for branching fractions are, in units of 10^{-6} (upper limits at 90% C.L.): BR(B+ -> etarho+) = 9.9 +/- 1.2 +/- 0.8, BR(B0 -> eta'eta) = 0.5 +/- 0.4 +/- 0.1 (<1.2), BR(B0 -> etapi0) = 0.9 +/- 0.4 +/- 0.1 (<1.5), BR(B0 -> eta'pi0) = 0.9 +/- 0.4 +/- 0.1 (<1.5), and BR(B0 -> omegapi0) = 0.07 +/- 0.26 +/- 0.02 (<0.5). The first error quoted is statistical and the second systematic. For the etarho+ mode, we measure the charge asymmetry Ach(B+ -> etarho+) = 0.13 +/- 0.11 +/- 0.02.

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Measurements of e+e- -> K+K-eta, K+K-pi0 and KsK+pi- Cross Sections Using Initial State Radiation Events

This paper reports measurements of processes: e+e- -> gamma KsK+pi-, e+e- -> gamma K+K-pi0, e+e- -> gamma phi eta, and e+e- -> gamma phi pi0. The initial state radiated photon allows to cover the hadronic final state in the energy range from thresholds up to ~4.6 GeV. The overall size of the data sample analyzed is 232 fb-1, collected by the BaBar detector running at the PEP-II e+e- storage ring. From the Dalitz plot analysis of the KsK+pi- final state, moduli and relative phase of the isoscalar and the isovector components of the e+e- -> K K*(892) cross section are determined. Parameters of phi and rho recurrences are also measured, using a global fitting procedure which exploits the interconnection among amplitudes, moduli and phases of the e+e- -> KsK+pi-, K+K-pi0, phi eta final states. The cross section for the OZI-forbidden process e+e- -> phi pi0, and the J/psi branching fractions to KK*(892) and K+K-eta are also measured.

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Evidence for CP violation in B0->J/Psi pi0 decays

We present measurements of the branching fraction and time-dependent CP asymmetries in B0->J/Psi pi0 decays based on 466 million Y(4S)->BBbar events collected with the BaBar detector at the SLAC PEP-II asymmetric-energy B factory. We measure the CP asymmetry parameters S=-1.23 +/- 0.21 +/- 0.04 and C=-0.20 +/- 0.19 +/- 0.03, where the measured value of S is 4.0 standard deviations from zero including systematic uncertainties. The branching fraction is determined to be B(B0->J/Psi pi0)=(1.69 +/- 0.14 +/- 0.07)*10^{-5}.

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Measurement of the Branching Fractions of the Rare Decays B0->Ds(*)+pi-, B0->Ds(*)+rho-, and B0->Ds(*)-K(*)+

We report the measurement of the branching fractions of the rare decays B0->Ds(*)+pi-, B0->Ds(*)+rho-, and B0->Ds(*)-K(*)+ in a sample of 381 million Y(4S) decays into BBbar pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+e- storage ring. We present evidence for the decay B0->Ds-K*+ and the vector-vector decays B0->Ds*+rho- and B0->Ds*-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(*)pi) and r(D(*)rho) in decays B0->D(*)pi and B0->D(*)rho, and comment on the prospects for measuring the CP observable sin(2beta+gamma).

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Observation of B-meson decays to b_1 pi and b_1 K

We present the results of searches for decays of B mesons to final states with a b_1 meson and a charged pion or kaon. The data, collected with the BaBar detector at the Stanford Linear Accelerator Center, represent 382 million B-Bbar pairs produced in e+e- annihilation. The results for the branching fractions are, in units of 10^{-6}, B(B+ -> b1^0 pi+) = 6.7 +/- 1.7 +/- 1.0 (4.0 sigma), B(B+ -> b1^0 K+ = 9.1+/- 1.7+/- 1.0 (5.3 sigma), B(B0 -> b1^-/+ pi^+/-) = 10.9 +/- 1.2 +/- 0.9 (8.9 sigma), and B(B0 -> b1^-K+) = 7.4 +/- 1.0 +/- 1.0 (6.1 sigma), with the assumption that B(b_1 -> omega pi)=1. We also measure charge and flavor asymmetries Ach(B+ -> b1^0 pi+) = 0.05 +/- 0.16 +/- 0.02, Ach(B+ -> b1^0 K+ = -0.46 +/- 0.20 +/- 0.02, Ach(B0 -> b1^-/+ pi^+/-) = -0.05 +/- 0.10 +/- 0.02, C(B0 -> b1^-/+ pi^+/-) = -0.22 +/- 0.23 +/- 0.05, deltaC(B0 -> b1^-/+ pi^+/-) = -1.04 +/- 0.23 +/- 0.08, and Ach(B0 -> b1^-K+) = -0.07 +/- 0.12 +/- 0.02, The first error quoted is statistical, the second systematic, and for the branching fractions, the significance is given in parentheses.

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A study of B->X(3872) K, with X(3872)->J/Psi pi+ pi-

We present measurements of the decays B+ -> X(3872) K+ and B0 -> X(3872) K0 with X(3872) -> Jpsi pi+ pi-. The data sample used, collected with the BABAR detector at the PEP-II e+e- asymmetric-energy storage ring, corresponds to 455 x 10^6 BBbar pairs. Branching fraction measurements of BF(B+ -> X(3872) K+) x BF(X(3872) -> Jpsi pi+ pi-) = (8.4 +/- 1.5 +/- 0.7) x 10^{-6} and BF(B0 -> X(3872) K0) x BF(X(3872) -> Jpsi pi+ pi- = (3.5 +/- 1.9 +/- 0.4) x 10^{-6} are obtained. We set an upper limit on the natural width of the X(3872) of Gamma < 3.3 MeV/c^2 at the 90% confidence level.

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Measurement of the B --> X_s gamma Branching Fraction and Photon Energy Spectrum using the Recoil Method

We present a measurement of the branching fraction and photon energy spectrum for the decay B --> X_s gamma using data from the BaBar experiment. The data sample corresponds to an integrated luminosity of 210 fb^{-1}, from which approximately 680 000 BB events are tagged by a fully reconstructed hadronic decay of one of the B mesons. In the decay of the second B meson, an isolated high--energy photon is identified. We measure BR(B --> X_s gamma) = (3.66 +- 0.85_{stat} +- 0.60_{syst}) x 10^{-4} for photon energies E_gamma above 1.9 GeV in the B rest frame. From the measured spectrum we calculate the first and second moments for different minimum photon energies, which are used to extract the heavy-quark parameters m_b and mu_{pi}^2. In addition, measurements of the direct CP asymmetry and isospin asymmetry are presented.

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Measurement of the tau -> 3pi eta nu Branching Fraction and a Search for a Second-Class Current in the tau -> eta'(958) pi nu Decay

The "τ\to 3πην" decay with the "η\to γγ" mode is studied using 384 fb^-1 of data collected by the BaBar detector. The branching fraction is measured to be (1.60+/-0.05+/-0.11)x10^-4. It is found that "τ\to f1 πνto 3πην" is the dominant decay mode with a branching fraction of (1.11+/-0.06+/-0.05)x10^-4. The first error on the branching fractions is statistical and the second systematic. In addition, a 90% confidence level upper limit on the branching fraction of the "τ\to η'(958) πν" decay is measured to be 7.2x10^-6. This last decay proceeds through a second-class current and is expected to be forbidden in the limit of isospin symmetry.

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Measurement of the Spin of the Xi(1530) Resonance

The properties of the Xi(1530) resonance are investigated in the Lambdac+ --> Xi- pi+ 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 inverse fb. The spin of the Xi(1530) is established to be 3/2. The existence of an S-wave amplitude in the Xi- pi+ system is inferred, and its interference with the Xi(1530)0 amplitude provides the first clear demonstration of the Breit-Wigner phase motion expected for the Xi(1530). The P_1(cos[theta(Xi-)]) Legendre polynomial moment indicates the presence of a significant S-wave amplitude for Xi- pi+ mass values above 1.6 GeV/c^2, and a dip in the mass distribution at approximately 1.7 GeV/c^2 is interpreted as due to coherent addition of a Xi(1690)0 contribution to this amplitude. This would imply J^P=1/2^- for the Xi(1690). Attempts at fitting the Xi(1530)0 lineshape yield unsatisfactory results, and this failure is attributed to interference effects associated with the amplitudes describing the K+ pi+ and/or Xi- K+ systems.

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Determination of the Form Factors for the Decay B0 -> D*- l+ nu_l and of the CKM Matrix Element |V_cb|

We present a combined measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V_{cb}| and of the parameters rho^2, R_1(1), and R_2(1), which fully characterize the form factors for the B0 -> D*- l+ nu_l decay in the framework of heavy-quark effective theory. The results, based on a selected sample of about 52,800 B0 -> D*- l+ nu_l decays, recorded by the BaBar detector, are rho2=1.157+-0.094+-0.027, R_1(1)=1.327+-0.131+-0.043, R_2(1)=0.859+-0.077+-0.021, and F(1)|V_cb|=(34.7+-0.4+-1.0)x10^-3. The first error is the statistical and the second is the systematic uncertainty. Combining these measurements with the previous BaBar measurement of the form factors, which employs a different fit technique on a partial sample of the data, we improve the statistical precision of the result, rho2=1.191+-0.048+-0.028, R_1(1)=1.429+-0.061+-0.044, R_2(1)=0.827+-0.038+-0.022, and F(1)|V_cb| = (34.4+-0.3+-1.1)x10^-3. Using lattice calculations for the axial form factor $\mathcal{F}(1)$, we extract |V_cb| =(37.4+-0.3+-1.2+1.2-1.4)x10^-3, where the third error is due to the uncertainty in F(1). We also present a measurement of the exclusive branching fraction, B = (4.69+-0.04+-0.34)%.

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Observation of tree-level B decays with $s\bar{s}$ Production from Gluon Radiation

We report on our search for $B^- \to D^{(*)+}_s K^- π^-$, $\bar{B^0} \to D_s^{(*)+} K_S^0 π^-$, and $B^- \to D^{(*)+}_s K^- K^-$ decays in 383 million $\FourS \to B \Bbar$ events collected by the Babar detector at the PEP2 asymmetric-energy $B$-factory. The decays proceed via a tree-level $b\to c$ quark transition in which a gluon radiates into an $s\bar{s}$ pair. Their branching fractions are measured to be ${\cal B}(B^- \to D^+_s K^- π^-) = (2.02 \pm 0.13_{stat} \pm 0.38_{syst}) \times 10^{-4},$ ${\cal B}(B^- \to D^{*+}_s K^- π^-)= (1.67 \pm 0.16_{stat} \pm 0.35_{syst}) \times 10^{-4},$ ${\cal B}(\bar{B^0} \to D_s^{+} K_S^0 π^-)= (0.55 \pm 0.13_{stat} \pm 0.10_{syst}) \times 10^{-4},$ and ${\cal B}(B^- \to D_s^{+} K^- K^-) = (0.11 \pm 0.04_{stat} \pm 0.02_{syst}) \times 10^{-4}$. Upper limits at the 90% C.L. are set on ${\cal B}(\bar{B^0} \to D_s^{*+} K_S^0 π^-)< 0.55 \times 10^{-4}$ and ${\cal B}(B^- \to D_s^{*+} K^- K^-) < 0.15 \times 10^{-4}$. We present evidence that the invariant mass distributions of $D^{(*)+}_s K^-$ pairs from $B^- \to D^{(*)+}_s K^- π^-$ decays are inconsistent with the phase-space model, suggesting the presence of charm resonances lying below the $D^{(*)+}_s K^-$ threshold.

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Measurement of the Absolute Branching Fraction of D0 --> K- pi+

We measure the absolute branching fraction for D0 --> K- pi+ using partial reconstruction of B0bar --> D^{*+} X \ell^{-} \barν_{\ell} decays, in which only the charged lepton and the pion from the decay D^{*+} --> D0 pi^+ are used. Based on a data sample of 230 million B Bbar pairs collected at the Upsilon(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, we obtain the absolute branching fractions of D0 --> K- pi+ = (4.007 \pm 0.037 \pm 0.072)%, where the first uncertainty is statistical and the second is systematic.

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