arXiv subjects

B. Aubert

Publications and source records attributed to B. Aubert.

At least 91 records · Page 5Linked to original sources

arXiv2008

Measurement of Ratios of Branching Fractions and CP-Violating Asymmetries of B -> D*K Decays

We report a study of B -> D*K decays with D* decaying to D pi0 or D gamma, using 383 * 10**6 B Bbar pairs collected at the Upsilon(4S) resonance with the BaBar detector at the SLAC PEP-II B-Factory. The D meson decays under study include a non-CP mode (Kpi), CP-even modes (K+K-, pi^+pi^-) and CP-odd modes (KS pi0, KS phi, KS omega). We measure ratios (R*_{CP+-}) of branching fractions of decays to CP eigenmode states and to flavor-specific states as well as CP asymmetries (A*_{CP+-}). These measurements are sensitive to the unitarity triangle angle gamma. We obtain A*_{CP+} = -0.11 pm 0.09 pm 0.01, R*_{CP+} = ~1.31 pm 0.13 pm 0.04, and A*_{CP-} = 0.06 pm 0.10 pm 0.02, R*_{CP-} = ~1.10 pm 0.12 pm 0.04, where the first error is statistical and the second error is systematic. Translating our results into an alternative parametrization, widely used for related measurements, we obtain x*_{+}=0.11 pm 0.06 pm 0.02 and x*_{-} = 0.00 pm 0.06 pm 0.02. No significant CP-violating charge asymmetry is found in either the flavor-specific mode D -> K pi or in B -> D* pi decays.

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arXiv2008

Time-dependent and time-integrated angular analysis of $B\toϕK^0_Sπ^0$ and $ϕK^\pmπ^\mp$

We perform a time-dependent and time-integrated angular analysis of the decays $B^0\toϕK^{*}(892)^0$, $ϕK^{*}_2(1430)^0$, and $ϕ(Kπ)^{*0}_{0}$ with the final sample of about 465 million $\BB$ pairs recorded with the $\babar$ detector. Twenty-four parameters are investigated, including the branching fractions, CP-violation parameters, and parameters sensitive to final-state interactions. We use the dependence on the $Kπ$ invariant mass of the interference between the scalar and vector or tensor components to resolve discrete ambiguities of the strong and weak phases. We use the time-evolution of the $B\toϕK^0_Sπ^0$ channel to extract the CP-violation phase difference $Δϕ_{00}=0.28\pm0.42\pm 0.04$ between the $B$ and $\Bbar$ decay amplitudes. When the $B\toϕK^\pmπ^\mp$ channel is included, the fractions of longitudinal polarization ${f_L}$ of the vector-vector and vector-tensor decay modes are measured to be $0.494\pm0.034\pm0.013$ and $0.901^{+0.046}_{-0.058}\pm 0.037$, respectively. This polarization pattern requires the presence of a positive-helicity amplitude in the vector-vector decay from a currently unknown source.

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arXiv2008

Measurement of the e+e- --> b anti-b cross section between sqrt(S)=10.54 and 11.20 GeV

We report e+e- --> b anti-b cross section measurements by the BABAR experiment performed during an energy scan in the range of 10.54 to 11.20 GeV at the PEP-II e+e- collider. A total relative error of about 5% is reached in more than three hundred center-of-mass energy steps, separated by about 5 MeV. These measurements can be used to derive precise information on the parameters of the Y(10860) and Y(11020) resonances. In particular we show that their widths may be smaller than previously measured.

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arXiv2008

Search for CP Violation in Neutral D Meson Cabibbo-suppressed Three-body Decays

Using 385 fb^-1 of e^+e^- collision data collected at center-of-mass energies around 10.6 GeV, we search for time-integrated CP violation in the singly Cabibbo-suppressed decays D0/D0bar --> pi^- pi^+ pi^0 and D0/D0bar --> K^- K^+ pi^0. Our model-independent and model-dependent analyses show no evidence of CP violation in these decays. The intermediate amplitudes include well-defined flavor states [e.g., rho(770)^+- pi^-+, K*(892)^+- K^-+] and CP-odd eigenstates [e.g., rho(770)^0 pi^0, phi(1020) pi^0]. With the null results of the previous analyses for CP-even eigenstates D0/D0bar --> K^+ K^- and D0/D0bar --> pi^+ pi^-, we conclude that any CP violation in the singly Cabibbo-suppressed charm decays occurs at a rate which is not larger than a few percent. These results are in accord with the Standard Model predictions, and provide constraints on some models beyond the Standard Model.

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arXiv2008

A Search for $B^+ \to \ell^+ ν_{\ell}$ Recoiling Against $B^{-}\to D^{0} \ell^{-}\barν X$

We present a search for the decay $\B^+ \to \ell^+ ν_{\ell} (\ell = τ, μ, \mathrm{or} e)$ in $(458.9 \pm 5.1) \times 10^{6}$ $Υ(4S)$ decays recorded with the Babar detector at the SLAC PEP-II $B$-Factory. A sample of events with one reconstructed exclusive semi-leptonic B decay ($B^{-}\to D^{0} \ell^{-}\barν X$) is selected, and in the recoil a search for $\B^+ \to \ell^+ ν_{\ell}$ signal is performed. The $τ$ is identified in the following channels: $τ^+ \to e^+ ν_e \overlineν_τ$, $τ^+ \to μ^+ ν_μ \overlineν_τ$, $τ^+ \to π^+ \overlineν_τ$, and $τ^+ \to π^+ π^{0} \overlineν_τ$. The analysis strategy and the statistical procedure is set up for the branching fraction extraction or upper limit determination. We determine from the dataset a preliminary measurement of $\mathcal{B}(\B^+ \to τ^+ ν_τ) = (1.8 \pm 0.8 \pm 0.1) \times 10^{-4}$, which excludes zero at $2.4 σ$, and $f_{B} = 230 \pm 57 \mev $. Combination with the hadronically tagged measurement yields $\mathcal{B}(\B^+ \to τ^+ ν_τ) = (1.8 \pm 0.6) \times 10^{-4}$. We also set preliminary limits on the branching fractions at $\mathcal{B}(\B^+ \to e^+ ν_{e}) < 7.7 \times 10^{-6} (\textrm{90% C.L.})$, $\mathcal{B}(\B^+ \to μ^+ ν_μ) < 11 \times 10^{-6} (\textrm{90% C.L.})$, and $\mathcal{B}(\B^+ \to τ^+ ν_τ) < 3.2 \times 10^{-4} (\textrm{90% C.L.})$.

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arXiv2008

Observation of Y(3940) -> J/psi omega in B -> J/psi omega K at BABAR

We present a study of the decays $B^{0,+}\to J/ψωK^{0,+}$ using $383\times 10^{6}$ $B\bar{B}$ events obtained with the \babar detector at PEP-II. We observe $Y(3940) \to J/ψω$, with mass $3914.6 ^{+3.8}_{-3.4} (stat) \pm{2.0} (syst)$ \mevcc, and width $34^{+12}_{-8}(stat)\pm{5}(syst)$ \mev. The ratio of $B^0$ and $B^+$ decay to $YK$ is $0.27^{+0.28}_{-0.23}(stat)^{+0.04}_{-0.01}(syst)$, and the relevant $B^0$ and $B^+$ branching fractions are reported.

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arXiv2008

Dalitz Plot Analysis of the Decay B0(B0bar) --> K+/- pi-/+ pi0

We report a Dalitz-plot analysis of the charmless hadronic decays of neutral B mesons to K^+/- pi^-/+ pi^0. With a sample of (231.8+/-2.6) 10^6 Upsilon(4S) to B Bbar decays collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, we measure the magnitudes and phases of the intermediate resonant and nonresonant amplitudes for B0 and B0bar decays and determine the corresponding CP-averaged branching fractions and charge asymmetries. The inclusive branching fraction and CP-violating charge asymmetry are measured to be BF(B0 --> K+ pi^- pi0)=(35.7-1.5+2.6 +/-2.2)10^(-6), and A_CP=-0.030+0.045-0.051 +/-0.055 where the first errors are statistical and the second systematic. We observe the decay B0 --> K^{*0}(892) pi^0 with the branching fraction BF(B0 --> K^{*0}(892) pi^0)=(3.6_{-0.8}^{+0.7} +/-0.4) 10^{-6}. This measurement differs from zero by 5.6 standard deviations (including the systematic uncertainties). The selected sample also contains B0 --> D^0bar pi^0 decays where D^0bar --> K+ pi-, and we measure BF(B0 --> D0bar pi^0)=(2.93 +/- 0.17 +/-0.18) 10^{-4}.

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arXiv2008

Amplitude Analysis of the Decay B0 -> K+pi-pi0

We report an updated amplitude analysis of the charmless hadronic decays of neutral B mesons to K+pi-pi0. With a sample of 454 million Upsilon(4S) -> B0B0bar decays collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, we measure the magnitudes and phases of the intermediate resonant and nonresonant amplitudes for B0 and B0bar decays and determine the corresponding CP-averaged fit fractions and charge asymmetries.

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arXiv2008

Measurement of Branching Fractions and CP and Isospin Asymmetries in B -> K* gamma

We present a preliminary analysis of the decays B0 -> K*0 gamma and B+ -> K*+ gamma using a sample of 383 x 10^6 BBbar events collected with the BABAR dector at the PEP-II asymmetric energy B factory. We measure the branching fractions BF(B0 -> K*0 Gamma) = (4.58 +/- 0.11 +/- 0.16) x 10^-5 and BF(B+ -> K*+ Gamma) = 4.73 +/- 0.15 +/- 0.17 x 10^-5. We measure the direct CP asymmetry to be -0.043 < A(B -> K* gamma) < 0.025 and the isospin asymmetry to be -0.021 < Delta0- < 0.079, where the limits are determined at the 90% confidence interval and include both the statistical and systematic uncertainties.

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arXiv2008

Update of Time-Dependent CP Asymmetry Measurements in $b$-->$c\bar{c}s$ Decays

We present updated measurements of time-dependent CP asymmetries in fully reconstructed neutral B decays containing a charmonium meson. The measurements reported here use a data sample of $(465\pm 5)\times 10^6$ $Υ(4S) \to B \bar{B}$ decays collected with the BABAR detector at the PEP-II $B$ factory. The time-dependent CP asymmetry parameters measured from $J/ψK_S^0$, $J/ψK_L^0$, $ψ(2S) K_S^0$, $χ_{c1} K_S^0$, $η_c K_S^0$, and $J/ψK^{*0}$ decays are \begin{eqnarray} C_f &=& 0.026 \pm 0.020(stat) \pm 0.016(syst), S_f &=& 0.691 \pm 0.029(stat) \pm 0.014(syst). \end{eqnarray}

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arXiv2008

Measurement of the Branching Fractions of the Radiative Charm Decays $D^{0} \to {\bar K}^{*0} γ$ and $D^{0} \to ϕγ$

We present a measurement of the branching fractions for the Cabibbo-favored radiative decay, $D^{0} \to {\bar K}^{*0} γ$, and the Cabibbo-suppressed radiative decay, $D^{0} \to ϕγ$. These measurements are based on a data sample corresponding to an integrated luminosity of $387.1 fb^{-1}$, recorded with the BaBar detector at the PEP-II $e^+e^-$ asymmetric-energy collider operating at center-of-mass energies 10.58 and 10.54 GeV. We measure the branching fractions relative to the well-studied decay $D^{0} \to K^{-} π^{+}$ and find ${\cal B}(D^{0} \to {\bar K}^{*0} γ)/{\cal B}(D^{0} \to K^{-} π^{+}) = (8.43 \pm 0.51 \pm 0.70) \times 10^{-3}$ and ${\cal B}(D^{0} \to ϕγ)/{\cal B}(D^{0} \to K^{-} π^{+}) = (7.15 \pm 0.78 \pm 0.69) \times 10^{-4}$, where the first error is statistical and the second is systematic. This is the first measurement of ${\cal B}(D^{0} \to {\bar K}^{*0} γ)$.

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arXiv2008

Study of the pi+pi-J/psi Mass Spectrum via Initial-State Radiation at BABAR

We present an update of the study of the Y(4260) resonance, produced in the process $e^+e^-\toγ_{ISR} π^+π^-J/ψ$ using initial-state radiation events at the PEP-II $e^+e^-$ storage rings. This study is based on 454fb$^{-1}$ of data recorded with the {\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}} detector at a center-of-mass energy in the $Υ(4S)$ resonance region. From a fit with a single non-relativistic Breit-Wigner shape we obtain updated parameters for the Y(4260) resonance which are $m_Y = 4252 \pm6 ^{+2}_{-3}$MeV/c$^2$ and $Γ_Y = 105 \pm 18^{+4}_{-6}$MeV/c$^2$; we also measure ${\calB}(π^+π^-J/ψ)Γ_{e^+e^-} = (7.5\pm 0.9 \pm0.8)$ eV. We cannot confirm the recent BELLE observation of a broad structure around 4.05GeV/c$^2$ in this decay mode.

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arXiv2008

Measurement of the branching fraction B(tau- --> K0 pi- nu) using the BaBar detector

A preliminary measurement of the branching fraction B(tau- --> K0 pi- nu) is made using 384.6 fb-1 of e+e- collision data provided by the PEP-II collider, operating primarily at sqrt(s)=10.58 GeV, and recorded using the BaBar detector. From this we measure: B(tau- --> K0 pi- nu) = (0.840 +/- 0.004 (stat) +/- 0.023 (syst)) %. This result is the most precise measurement to date and is consistent with the world average.

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arXiv2008

Measurements of Branching Fractions for B+ -> rho+ gamma, B0 -> rho0 gamma, and B0 -> omega gamma

We present branching fraction measurements for the radiative decays B+ -> rho+ gamma, B0 -> rho0 gamma, and B0 -> omega gamma. The analysis is based on a data sample of 465 million BBbar events collected with the BaBar detector at the PEP-II asymmetric B factory. We find BR(B+ -> rho+ gamma) = (1.20 +0.42 -0.37 +/-0.20) x 10^-6, BR(B0 -> rho0 gamma) = (0.97 +0.24 -0.22 +/-0.06) x 10^-6, and a 90% C.L. upper limit BR(B0 -> omega gamma) < 0.9 x 10^-6, where the first error is statistical and the second is systematic. We also measure the isospin-violating quantities Gamma(B+ -> rho+ gamma) / 2Gamma(B0 -> rho0 gamma) - 1 = -0.43 +0.25 -0.22 +/-0.10.

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arXiv2008

Improved measurement of the CKM angle gamma in B^-+ -> D^() K^()-+ decays with a Dalitz plot analysis of D decays to K_S^0 pi^+ pi^- and K_S^0 K^+ K^-

We report on an improved measurement of the Cabibbo-Kobayashi-Maskawa {\it CP}-violating phase $γ$ through a Dalitz plot analysis of neutral $D$ meson decays to $K_S^0 π^+ π^-$ and $K_S^0 K^+ K^-$ in the processes $B^\mp \to D K^\mp$, $B^\mp \to D^* K^\mp$ with $D^* \to Dπ^0,Dγ$, and $B^\mp \to D K^{*\mp}$ with $K^{*\mp} \to K_S^0 π^\mp$. Using a sample of 383 million $B\bar{B}$ pairs collected by the BABAR detector, we measure $γ=(76 \pm 22 \pm 5 \pm 5)^\circ$ (mod $180^\circ$), where the first error is statistical, the second is the experimental systematic uncertainty and the third reflects the uncertainty on the description of the Dalitz plot distributions. The corresponding two standard deviation region is $29^\circ < γ< 122^\circ$. This result has a significance of direct {\it CP} violation ($γ\ne 0$) of 3.0 standard deviations.

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arXiv2008

Measurement of the color-suppressed decays anti-B0->D(*)0 pi0 /omega/eta/eta prime branching fractions

We report results on the branching fraction ($\mathcal{BF}$) measurement of the color-suppressed decays $\bar{B}^0\to D^0 π^0$, $D^{*0}π^0$, $D^0η$, $D^{*0}η$, $D^0ω$, $D^{*0}ω$, $D^0η^{\prime}$, and $D^{*0}η^{\prime}$. The result is based on a sample of $(454\pm 5)\times 10^{6} B\bar{B}$ pairs collected at the $Υ(4S)$ resonance from 1999 to 2007, with the $\babar$ detector at the PEP-II storage rings at the Stanford Linear Accelerator Center. The measurements are compared to theoretical predictions by factorization, SCET and pQCD.

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arXiv2008

Search for B+ meson decay to a1+ K*0

We present the preliminary result of a search for the decay B+- --> a1+-K*0. The data, collected with the BaBar detector at the Stanford Linear Accelerator Center, represent 465 million BB pairs produced in e+e- annihilation at the Y(4s) energy. The result for the branching fraction is: B(B+ --> a1+ K*0) * B(a1+ --> pi+pi-pi+) = (0.7 +0.5/-0.4 +/-0.7) x 10-6, corresponding to an upper limit at 90% confidence level of 1.6 x 10-6. The first error quoted is statistical, the second systematic.

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arXiv2008

Measurement of the Branching Fractions of Bbar -> D** l^- nubar_l Decays in Events Tagged by a Fully Reconstructed B Meson

We report a measurement of the branching fractions of Bbar -> D** l^- nubar_l decays based on 417 fb-1 of data collected at the Upsilon(4S) resonance with the BaBar detector at the PEP-II e+e- storage rings. Events are selected by fully reconstructing one of the B mesons in a hadronic decay mode. A fit to the invariant mass differences m(D(*)pi)-m(D(*)) is performed to extract the signal yields of the different D** states. We observe the Bbar -> D** l^- nubar_l decay modes corresponding to the four D** states predicted by Heavy Quark Symmetry with a significance greater than six standard deviations including systematic uncertainties.

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