arXiv subjects

B. Aubert

Publications and source records attributed to B. Aubert.

At least 325 records · Page 18Linked to original sources

arXiv2006

A Search for the Decay B+ --> tau+ nu_tau

We search for the rare leptonic decay B+ --> tau+ nu_tau in a sample of 232x10^6 BBbar pairs collected with the BABAR detector at the SLAC PEP-II B-Factory. Signal events are selected by examining the properties of the B meson recoiling against the semileptonic decay B- --> D*0 l- nu_lbar. We find no evidence for a signal and set an upper limit on the branching fraction of BR(B+ --> tau+ nu_tau) < 2.8x10^{-4} at the 90% confidence level. We combine this result with a previous, statistically independent BABAR search for B+ --> tau+ nu_tau to give an upper limit of BR(B+ --> tau+ nu_tau) < 2.6x10^{-4} at the 90% confidence level.

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arXiv2006

The e+ e- --> 3(pi+pi-), 2(pi+pi-pi0) and K+K- 2(pi+pi-) Cross Sections at Center-of-Mass Energies from Production Threshold to 4.5 GeV Measured with Initial-State Radiation

We study the processes e+ e- --> 3(pi+pi-)gamma, 2(pi+pi-pi0)gamma and K+ K- 2(pi+pi-)gamma, with the photon radiated from the initial state. About 20,000, 33,000 and 4,000 fully reconstructed events, respectively, have been 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 these data can be compared with the corresponding direct e+e- measurements. From the 3(pi+pi-), 2(pi+pi-pi0) and K+ K- 2(pi+pi-) mass spectra, the cross sections for the processes e+ e- --> 3(pi+pi-), e+ e- --> 2(pi+pi-pi0) and e+ e- --> K+ K- 2(pi+pi-) are measured for center-of-mass energies from production threshold to 4.5 GeV. The uncertainty in the cross section measurement is typically 6-15%. We observe the J/psi in all these final states and measure the corresponding branching fractions.

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arXiv2006

Search for Lepton Flavor Violation in the Decay tau -> electron gamma

A search for the non-conservation of lepton flavor in the decay tau -> electron gamma has been performed with 2.07 x 10^8 e+e- -> tau+ tau- events collected by the BABAR detector at the PEP-II storage ring at a center-of-mass energy near 10.58 GeV. We find no evidence for a signal and set an upper limit on the branching ratio of BR(tau -> electron gamma) < 1.1 x 10^-7 at 90% confidence level.

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arXiv2006

Measurement of Branching Fractions and Resonance Contributions for B0 -> D0bar K+ pi- and Search for B0 -> D0 K+ pi- Decays

Using 226 million $Υ(4S)\to B\bar{B}$ events collected with the BaBar detector at the PEP-II $e^+e^-$ storage ring at the Stanford Linear Accelerator Center, we measure the branching fraction for $B^0\to \bar{D}^0 K^+π^-$, excluding $B^0\to D^{*-} K^+$ to be $ {\cal B}(B^0\to \bar{D}^0 K^+π^-) = (88 \pm 15 \pm 9)\times 10^{-6} . $ We observe $B^0\to \bar{D}^0 K^*(892)^0$ and $B^0\to D_2^*(2460)^- K^+$ contributions. The ratio of branching fractions ${\cal B}(B^0\to D^{*-}K^+)/{\cal B}(B^0\to D^{*-}π^+) = (7.76\pm 0.34 \pm 0.29)%$ is measured separately. The branching fraction for the suppressed mode $B^0\to D^0 K^+π^-$ is $ {\cal B}(B^0\to D^0 K^+π^-) < 19 \times 10^{-6} $ at the 90% confidence level.

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arXiv2005

Measurements of the branching fractions and CP-asymmetries of B- --> D0_(CP) K- decays

We present a study of the decay B- --> D0_(CP) K- and its charge conjugate, where D0_(CP) is reconstructed in CP-even, CP-odd, and non-CP flavor eigenstates, based on a sample of 232 million Y(4S) --> B Bbar decays collected with the BABAR detector at the PEP-II e+e- storage ring. We measure the partial-rate charge asymmetries A_CP+, A_CP- and the ratios R_CP+, R_CP- of the B --> D0 K decay branching fractions as measured in CP+, CP-, and non-CP D0 decays: A_CP+ = 0.35 +/- 0.13 (stat) +/- 0.04 (syst) A_CP- = -0.06 +/- 0.13 (stat) +/- 0.04 (syst) R_CP+ = 0.90 +/- 0.12 (stat) +/- 0.04 (syst) R_CP- = 0.86 +/- 0.10 (stat) +/- 0.05 (syst)

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arXiv2005

Search for rare quark-annihilation decays, B --> Ds(*) Phi

We report on searches for B- --> Ds- Phi and B- --> Ds*- Phi. In the context of the Standard Model, these decays are expected to be highly suppressed since they proceed through annihilation of the b and u-bar quarks in the B- meson. Our results are based on 234 million Upsilon(4S) --> B Bbar decays collected with the BABAR detector at SLAC. We find no evidence for these decays, and we set Bayesian 90% confidence level upper limits on the branching fractions BF(B- --> Ds- Phi) < 1.9x10^(-6) and BF(B- --> Ds*- Phi)<1.2x10^(-5). These results are consistent with Standard Model expectations.

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arXiv2005

A study of e+e- -> p anti-p using initial state radiation with BABAR

The e+e- -> p anti-p cross section is determined over a range of p anti-p masses, from threshold to 4.5 GeV/c^2, by studying the e+e- -> p anti-p gamma process. The data set corresponds to an integrated luminosity of 232 fb^-1, collected with the BABAR detector at the PEP-II storage ring, at an e+e- center-of-mass energy of 10.6 GeV. The mass dependence of the ratio of electric and magnetic form factors, |G_E/G_M|, is measured for p anti-p masses below 3 GeV/c^2; its value is found to be significantly larger than 1 for masses up to 2.2 GeV/c^2. We also measure J/psi -> p anti-p and psi(2S) -> p anti-p branching fractions and set an upper limit on Y(4260) -> p anti-p production and decay.

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arXiv2005

Measurement of the Inclusive Electron Spectrum in Charmless Semileptonic B Decays Near the Kinematic Endpoint and Determination of |Vub|

We present a measurement of the inclusive electron spectrum in charmless semileptonic B decays near the kinematic limit for B->X_c eνtransitions, using a sample of 88 million Upsilon(4S) decays recorded by the BABAR detector. Partial branching fraction measurements are performed in five overlapping intervals of the electron momentum. For the interval of 2.0-2.6 GeV/c we obtain ΔBr(B->X_u eν) = (0.572+-0.041(stat)+-0.065(syst))x10^{-3}. Combining this result with shape function parameters extracted from BABAR measurements of moments of the inclusive photon spectrum in B->X_s+gamma decays and moments of the hadron mass and lepton energy spectra in B->X_c lνdecays we determine |V_{ub}|=((4.44+-0.25(exp) ^{+0.42}_{-0.38}(SF)+-0.22(theory))x10^{-3}. Here the first error represents the combined statistical and systematic experimental uncertainties of the partial branching fraction measurement, the second error refers to the uncertainty of the determination of the shape function parameters, and the third error is due to theoretical uncertainties in the QCD calculations.

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arXiv2005

Search for the Radiative Decay B --> phi gamma

We perform a search for the exclusive radiative decay B0 --> phi gamma, which is dominated by b d annihilation, in a sample of 124 million BB events collected with the BABAR detector at the PEP-II asymmetric-energy e+e- storage ring at SLAC. No significant signal is seen. We set an upper limit on the branching fraction BR(B0 --> phi gamma < 8.5x10-7) at the 90% confidence level.

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arXiv2005

Study of B --> pi l nu and B --> rho l nu decays and determination of |Vub|

We present an analysis of exclusive charmless semileptonic B-meson decays based on 83 million BBbar pairs recorded with the BABAR detector at the Upsilon(4S) resonance. Using isospin symmetry, we measure branching fractions B(B0 --> pi- l+ nu) = (1.38 +- 0.10 +- 0.16 +- 0.08) x 10^-4 and B(B0 --> rho- l+ nu) = (2.14 +- 0.21 +- 0.48 +- 0.28) x 10^-4, where the errors are statistical, experimental systematic, and due to form-factor shape uncertainties. We compare the measured distribution in q^2, the momentum-transfer squared, with theoretical predictions for the form factors from lattice QCD and light-cone sum rules, and extract the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |V_{ub}| = (3.82 +- 0.14 +- 0.22 +- 0.11 +0.88 -0.52) x 10^-3 from B --> pi l nu, where the fourth error reflects the uncertainty of the form-factor normalization.

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arXiv2005

Measurement of the Branching Ratios Gamma(D_s+ -> D_s+ pi0)/Gamma(D_s+ -> D_s+ gamma) and Gamma(D0+ -> D0 pi0)/Gamma(D0* -> D0 gamma)

Data samples corresponding to the isospin-violating decay $D_s^{*+}\to D_s^+ π^0$ and the decays $D_s^{*+}\to D_s^+γ$, $D^{*0}\to D^0π^0$ and $D^{*0}\to D^0γ$ are reconstructed using 90.4 ${\rm fb}^{-1}$ of data recorded by the BaBar detector at the PEP-II asymmetric-energy $e^+e^-$ collider. The following branching ratios are extracted: $Γ(D_s^{*+}\to D_s^+ π^0)/Γ(D_s^{*+}\to D_s^+γ) = 0.062\pm0.005 ({\rm stat.})\pm0.006 ({\rm syst.})$ and $Γ(D^{*0}\to D^0π^0)/Γ(D^{*0}\to D^0γ) = 1.74\pm0.02 ({\rm stat.})\pm0.13 ({\rm syst.})$. Both measurements represent significant improvements over present world averages.

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arXiv2005

Measurement of CP Observables for the Decays B+/- --> D0_CP K*+/-

Using a sample of 232 million Upsilon(4S) --> B Bbar events collected with the BABAR detector at the PEP-II B Factory in 1999-2004, we study B- --> D0 K*(892)- decays where K*- --> KS pi- and D0 --> K-pi+, K-pi+pi0, K-pi+pi+pi- (non-CP final states); K+K-, pi+pi- (CP+ eigenstates); KSpi0, KSphi and KSomega (CP- eigenstates). We measure four observables that are sensitive to the angle gamma of the CKM unitarity triangle; the partial-rate charge asymmetries A_CP+/- and the ratios of the B-decay branching fraction in CP+/- and non-CP decays R_CP+/-: A_CP+ = -0.08 +/- 0.19 (stat.) +/- 0.08 (syst.) A_CP- = -0.26 +/- 0.40 (stat.) +/- 0.12 (syst.) R_CP+ = 1.96 +/- 0.40 (stat.) +/- 0.11 (syst.) R_CP- = 0.65 +/- 0.26 (stat.) +/- 0.08 (syst.)

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arXiv2005

Search for the rare decay B0bar --> D*0 gamma

We report on a search for the rare decay B0bar --> D*0 gamma, which in the standard model is dominated by W-exchange. The analysis is based on a data sample comprising 87.8 x 10^6 BBbar pairs collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. No significant signal is observed, and an upper limit on the branching fraction of 2.5 x 10^{-5} at the 90% confidence level is obtained.

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arXiv2005

Search for the W-exchange decays B0 --> Ds()- Ds()+

We report a search for the decays $B^{0} \to D_{s}^{-} D_{s}^{+}$, $B^{0} \to D_{s}^{*-} D_{s}^{+}$, $B^{0} \to D_{s}^{*-} D_{s}^{*+}$ in a sample of 232 million $Υ(4S)$ decays to \BBb ~pairs collected with the \babar detector at the PEP-II asymmetric-energy $e^+ e^-$ storage ring. We find no significant signal and set upper bounds for the branching fractions: ${\cal B}(B^{0} \to D_{s}^{-} D_{s}^{+}) < 1.0 \times 10^{-4}, {\cal B}(B^{0} \to D_{s}^{*-} D_{s}^{+}) < 1.3 \times 10^{-4}$ and ${\cal B}(B^{0} \to D_{s}^{*-} D_{s}^{*+}) < 2.4 \times 10^{-4}$ at 90% confidence level.

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arXiv2005

Measurement of Time-Dependent CP Asymmetries and the CP-Odd Fraction in the Decay B0->D+D-

We present an updated measurement of time-dependent \CP asymmetries and the \CP-odd fraction in the decay $B^0 \to D^{*+}D^{*-}$ using $232 \times 10^{6} \BB$ pairs collected by the \babar detector at the PEP-II $B$ factory. We determine the \CP-odd fraction to be $0.125 \pm 0.044\stat \pm 0.007\syst$. The time-dependent \CP asymmetry parameters $C_+$ and $S_+$ are determined to be $0.06\pm 0.17\stat \pm 0.03\syst$ and $-0.75 \pm 0.25\stat \pm 0.03\syst$, respectively. The Standard Model predicts these parameters to be 0 and $-\stwob$, respectively, in the absence of penguin amplitude contributions.

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arXiv2005

Search for B -> J/psi D Decays

We report a search for B -> J/psi D decays, based on a sample of 124 10^6 BBbar events collected with the BABAR detector at the PEP-II storage ring of the Stanford Linear Accelerator Center. No significant signal is found. We obtain upper limits on the branching fractions of 1.3 10^{-5} for B0 -> J/psi D0bar and 1.2 10^{-4} for B+ -> J/psi D+ at 90% confidence level.

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arXiv2005

Measurement of the Partial Branching Fraction for Inclusive Charmless Semileptonic B Decays and Extraction of $|V_{ub}|$

Charmless semileptonic decays, ${\bar{B}} \to X_u \ell \barν$, are studied in a sample of 232 million $B\bar{B}$ decays recorded with the BaBar detector, in events where the decay of the second $B$ meson is fully reconstructed. Inclusive charmless decays are selected in kinematic regions where the dominant background from semileptonic B decays to charm is reduced by requirements on the hadronic mass $M_X$ and the momentum transfer $q^2$. The partial branching fraction for ${\bar{B}} \to X_u \ell \barν$ decays for $M_X<1.7$ GeV/c^2 and $q^2>8$ Gev^2/c^4 is measured to be $Δ{\cal{B}}({\bar{B}} \to X_u \ell \barν) = (0.87 \pm 0.09_{\rm stat}\pm 0.09_{\rm sys}\pm 0.01_{\rm th})\times 10^{-3}$. The CKM matrix element $|V_{ub}|$ is determined by using theoretical calculations of phase space acceptances. Theoretical uncertainties in this extrapolation are reduced by using the inclusive $b \to s γ$ photon spectrum and moments of the $b \to c \ell \barν$ lepton energy and hadronic invariant mass.

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arXiv2005

Production and decay of Xic0 at BABAR

Using 116.1 fb^-1 of data collected by the BABAR detector, we present an analysis of Xic0 production in B decays and from the ccbar continuum, with the Xic0 decaying into Omega- K+ and Xi- pi+ final states. We measure the ratio of branching fractions B(Xic0 -> Omega- K+)/B(Xic0 -> Xi- pi+) to be 0.294 +- 0.018 +- 0.016, where the first uncertainty is statistical and the second is systematic. The Xic0 momentum spectrum is measured on and 40 MeV below the Upsilon(4S) resonance. From these spectra the branching fraction product B(B -> Xic0 X) x B(Xic0 -> Xi- pi+) is measured to be (2.11 +- 0.19 +- 0.25) x 10^-4 and the cross-section product sigma(e+ e- -> Xic0 X) x B(Xic0 -> Xi- pi+) from the continuum is measured to be (388 +- 39 +- 41) fb at a center-of-mass energy of 10.58 GeV.

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