arXiv subjects

B. Aubert

Publications and source records attributed to B. Aubert.

At least 415 records · Page 23Linked to original sources

arXiv2004

Study of the decay B0(B0bar)-->rho+rho-, and constraints on the CKM angle alpha

Using a data sample of 89 million Y(4s)-->B0B0bar decays collected with the BaBar detector at the PEP-II asymmetric B Factory at SLAC, we measure the B0(B0bar)-->rho+rho- branching fraction as $(30\pm 4 stat \pm 5 syst) \times 10^{-6}$ and a longitudinal polarization fraction of $f_L = 0.99 \pm 0.03 stat ^{+0.04}_{-0.03} syst$. We measure the time-dependent-asymmetry parameters of the longitudinally polarized component of this decay as $C_L = -0.17\pm 0.27 stat \pm 0.14 syst$ and ${S_L} = -0.42 \pm 0.42 stat \pm 0.14 syst$. We present constraints on the CKM angle $α$.

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arXiv2004

Search for Lepton-Flavor Violation in the Decay tau -> lhh

A search for the lepton-flavor-violating decay of the tau into one charged lepton and two charged hadrons has been performed using $221.4 \mathrm{fb}^{-1}$ of data collected at an $e^+e^-$ center-of-mass energy around 10.58 GeV with the BABAR detector at the PEP-II storage ring. In all 14 decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range $(0.7-4.8)\times 10^{-7}$ at 90% confidence level. All results are preliminary.

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arXiv2004

Measurement of CP-Asymmetries for the Decays B+/- to D_cp Kstar+/- with the BABAR Detector

Using a sample of 227 million $Υ(4S) \to B \bar{B}$ events collected with the $BABAR$ detector at the PEP-II $B$ Factory in 1999--2004, we study $B^- \to D^0 K^*(892)^-$ decays where $K^{*-} \to K^0_S π^-$ and $D^0 \to K^-π^+, K^- π^+ π^0, K^-π^+ π^+ π^-$ (non-CP final states), $K^+ K^-, π^+ π^- (CP+$ eigenstates), $K^0_S~π^0, K^0_S ϕ$ and $K^0_S ω(CP-$ eigenstates). The partial rate charge asymmetries $\mathcal{A}_{CP}$ and the ratios $\mathcal{R}_{CP}$ defined in the literature as the sum of the $B^+$ and $B^-$ partial rates to a charged $K^*$ and a $D^0 CP$-eigenstate divi ded by the $B \to D^0 K^*$ decay rate, %of the \ensuremath{\Bu}\xspace\xspace m \ensuremath{\to}\xspace \Dcp \ensuremath{K^*}\xspacepm branch ing fractions summed over %\B charge to the \ensuremath{B^-}\xspace \xspace\ensuremath{\to}\xspace \ensuremath{D^0}\xspace \ensu remath{K^{*-}}\xspace branching fraction are sensitive to the angle $γ$ of the CKM unitarity triangle. We measure: \mathcal{A}_{CP+} &=&-0.09 \pm 0.20 (stat.) \pm 0.06 (syst.) \mathcal{A}_{CP-} &=& -0.33 \pm 0.34 (stat.) \pm 0.10 (syst.) (+1.15 \pm 0.12) \cdot (\mathcal{A}_{CP-} - \mathcal{A}_{CP+}) \mathcal{R}_{CP+} &=& +1.77 \pm 0.37 (stat.) \pm 0.12 (syst.) \mathcal{R}_{CP-} &=& +0.76 \pm 0.29 (stat.) \pm 0.06 (syst.) ^{- 0.04}_{-\ 0.14} The third uncertainty quoted for the CP- measurements reflects possible interference effects in the final states with $ϕ$ and $ω$ resonances. All results are preliminary.

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arXiv2004

D+ -> K-K+pi+ Meson Decays: A Search for CP Violation and a Measurement of the Branching Ratio

We present a preliminary measurement of the CP asymmetry in singly Cabibbo-suppressed D+ -> K-K+π+ decays and in the resonant decays D+ -> ϕπ+ and D+ -> K*0 K+. We use a data sample of 79.9 fb^{-1} recorded by the BABAR detector. The Cabibbo-favored Ds+ -> K-K+π+ branching fraction is used as normalization in the measurements to reduce systematic uncertainties. Preliminary results of the CP asymmetries obtained are A_{CP}(K+K-π\pm) = (1.4 \pm 1.0(stat.) \pm 1.1(syst.))\times 10^{-2}, A_{CP}(ϕπ\pm) = (0.2 \pm 1.5(stat.) \pm 0.8(syst.))\times 10^{-2}, and A_{CP}(K^{\pm} K*0) = (0.9 \pm 1.7(stat.) \pm 0.8(syst.))\times 10^{-2}. A preliminary determination of the branching ratio is \frac{Γ(D+ -> K-K+π+)}{Γ(D+ -> K-π+π+)} =(10.7 \pm 0.1(stat.) \pm 0.2(syst.))\times 10^{-2}.

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arXiv2004

Measurement of Time-Dependent CP Asymmetry in $B^0\to D^{(*)\pm}π^\mp$ Decays and Constraints on $sin(2β+γ)$

We present a measurement of time-dependent CP-violating asymmetries in fully reconstructed $B^0->D^{(*)\pm}π^\mp$ decays in a data sample of approximately 88 million $Y(4S)\to B\bar{B}$ decays collected with the BaBar detector at the PEP-II asymmetric-energy B factory at SLAC. We interpret the results in terms of the angles of the Cabibbo-Kobayashi-Maskawa unitarity triangle, and find $|sin(2β+γ)|>0.69$ at 68% confidence level. We exclude the hypothesis of no CP-violation ($sin(2β+γ) = 0$) at 83% confidence level.

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arXiv2004

Improved Measurement of CP Asymmetries in B0 -> (ccbar)K0(*) Decays

We present results on time-dependent CP asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 227 million Upsilon(4S) -> BBbar decays collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. The amplitude of the CP asymmetry, sin2Beta in the Standard Model, is derived from decay-time distributions from events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other $B$ meson is determined to be either a B0 or B0bar from its decay products. We measure sin2Beta = 0.722 +/- 0.040 (stat.) +/- 0.23 (syst.) in agreement with the Standard Model expectation.

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arXiv2004

Measurement of Neutral B Decay Branching Fractions to Kspi+pi- Final States

Branching fraction measurements using B-meson decays to Kspi+pi- are presented. These measurements were obtained by analyzing a data sample of 88.9 million Y(4S) --> BB decays collected with the BaBar detector at the SLAC PEP-II asymmetric-energy B factory. Using a maximum likelihood fit, the following branching fraction results were obtained: Br(B0 -> K0pi+pi- = (43.7 +/- 3.8 +/- 3.4) * 10^-6, Br(B0 --> K{*+}pi-) = (12.9 +/- 2.4 +/- 1.4) * 10$^-6} and Br(B0 --> D-(--> Kspi-)pi+ = (42.7 +/- 2.1 +/- 2.2) * 10^{-6}. The CP violating char ge asymmetry A(K*pi} for the decay B0 --> $K{*+}pi-$ was measured to be A(K*pi} = 0.23 +/- $0.18^{+0.09}_{-0.06}$. For all these measurements the first error is statistical and the second is systematic.

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arXiv2004

Measurement of the Branching Fractions for Inclusive $B^-$ and $\bar B^0$ Decays to Flavor-tagged $D$, $D_s$ and $Λ_c$

We report on the inclusive branching fractions of $B^-$ and of ${\bar B}^0$ mesons decaying to ${D^0 X}$, ${{\bar D}^0 X}$, ${D^+ X}$, ${D^- X}$, ${D_s^+ X}$, ${D_s^- X}$, ${Λ_c^+ X}$, ${{\bar Λ}_c^- X}$, based on a sample of 88.9 million $B \bar B$ events recorded with the $BABAR$ detector at the $Υ(4S)$ resonance. Events are selected by completely reconstructing one $B$ and searching for a reconstructed charmed particle in the rest of the event. We measure the number of charmed and of anti-charmed particles per $B$ decay and derive the total charm yield per $B^-$ decay, $n_c^- = 1.313 \pm 0.037 \pm 0.062 ^{+0.063}_{-0.042} $, and per ${\bar B}^0$ decay, $n_c^0 = 1.276 \pm 0.062 \pm 0.058 ^{+0.066}_{-0.046}$ where the first uncertainty is statistical, the second is systematic, and the third reflects the charm branching-fraction uncertainties.

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arXiv2004

Measurement of Time-Dependent CP-Violating Asymmetries in B0 Meson Decays to eta' K0

We present a preliminary measurement of CP-violating parameters S and C from fits of the time-dependence of B0 meson decays to eta' K0. The data were recorded with the BaBar detector at PEP-II and correspond to 227 * 10^6 B-Bbar pairs produced in e+e- annihilation through the Upsilon(4S) resonance. From a maximum likelihood fit we measure the CP-violation parameters S = 0.27 +/- 0.14 (stat) +/- 0.03 (syst) and C = -0.21 +/- 0.10 (stat) +/- 0.03 (syst).

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arXiv2004

Measurement of CP-Violating Asymmetries in B0->(rho pi)0 Using a Time-Dependent Dalitz Plot Analysis

We present the preliminary measurement of CP-violating asymmetries in B0->(rhopi)0->pi+pi-pi0 decays using a time-dependent Dalitz plot analysis. The results are obtained from a data sample of 213 million Y(4S)->BB-bar decays, collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. This analysis extends the narrow-rho quasi-two-body approximation used in the previous analysis, by taking into account the interference between the rho resonances of the three charges. We measure 16 coefficients of the bilinear form factor terms occurring in the time-dependent decay rate of the B0 meson with the use of a maximum-likelihood fit. We derive the physically relevant quantities from these coefficients. We measure the direct CP-violation parameters Acp = -0.088 +- 0.049 +- 0.013 and C = 0.34 +- 0.11 +- 0.05, where the first errors are statistical and the second systematic. For the mixing-induced CP-violation parameter we find S = -0.10 +- 0.14 +- 0.04, and for the dilution and strong phase shift parameters respectively, we obtain dC = 0.15 +- 0.11 +- 0.03 and dS = 0.22 +- 0.15 +- 0.03. For the angle alpha of the Unitarity Triangle we measure (113 +27 -17 +-6) deg, while only a weak constraint is achieved at the significance level of more than two standard deviations. Finally, for the relative strong phase delta+- between the B0->rho-pi+ and B0->rho+pi- transitions we find (-67 +28 -31 +- 7) deg, with a similarly weak constraint at two standard deviations and beyond.

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arXiv2004

Measurement of Time-Dependent CP Asymmetry in B0->D^(*)+-pi-+ Decays and Constraints on |sin(2beta+gamma)|

We present preliminary results of a time-dependent measurement of CP-violating asymmetry in fully reconstructed B0->D^(*)+-pi-+ decays in a data sample of approximately 88 million Y(4S)->BB decays collected with the BaBar detector at the PEP-II asymmetric-energy B factory at SLAC. We interpret the results in terms of the angles of the Cabibbo-Kobayashi-Maskawa unitarity triangle, and set the bound |sin(2beta+gamma)|>0.69 at 68% confidence level. We exclude sin(2beta+gamma) = 0 at 83% confidence level.

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arXiv2004

Search for the D_(sJ)(2632)^+ at BaBar

We have performed a search for the $D^*_{sJ}(2632)^+$ state recently reported by the SELEX Collaboration at FNAL. This preliminary analysis makes use of an integrated luminosity of 125 ${\rm fb}^{-1}$ collected by the BaBar detector at the PEP-II asymmetric-energy $e^+e^-$ collider. The resulting $D_s η$ and $D^0 K^+$ mass spectra show no evidence for the $D^*_{sJ}(2632)^+$ state. In addition, no signal is observed in the $D^{*+} K_S$ mass spectrum.

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arXiv2004

Search for decays of B0 mesons into pairs of charged leptons: B0->e+e-, B0->mu+mu-, B0->e+-mu-+

We present a search for the decays B0->e+e-, B0->mu+mu-, and B0->e+- mu-+ in data collected at the Y(4S) resonance with the Babar detector at the SLAC B Factory. Using a data set of 111 fb^-1, we find no evidence for a signal in any of the three channels investigated and set the following branching fraction upper limits at the 90% confidence level: B(B0->e+e-)< 6.1 x 10^-8, B(B0->mu+mu-) < 8.3 x 10^-8, and B(B0->e+-mu-+) < 18 x 10^-8.

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arXiv2004

A Search for B --> tau nu Recoiling against B --> D*0 l nu

We present a search for the decay $B^{+} \to τ^{+} ν_τ$ in $124.1 \times 10^{6}$ $Υ(4S)$ 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 ($B^- \to D^{*0} \ell^- \barν_{\ell}$) is selected, and in the recoil a search for $B^{+} \to τ^{+} ν_τ$ signal is performed. The $τ$ is identified in the following channels: $τ^+ \to e^+ ν_e \barν_τ$, $τ^+ \to μ^+ ν_μ \barν_τ$, $τ^+ \to π^+ \barν_τ$, $τ^+ \to π^+ π^{0} \barν_τ$, $τ^+ \to π^+ π^{-} π^{+} \barν_τ$. We find no evidence of signal, and we set a preliminary upper limit on the branching fraction of $\mathcal{B}(B^{+} \to τ^{+} ν_τ) < 4.3 \times 10^{-4}$ at the 90% confidence level (CL). This result is then combined with a statistically independent $BABAR$ search for $B^{+} \to τ^{+} ν_τ$ to give a combined preliminary limit of $\mathcal{B}(B^{+} \to τ^{+} ν_τ) < 3.3 \times 10^{-4}$ at 90% CL.

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arXiv2004

Measurements of Branching Fraction, Polarization, and Direct-CP-Violating Charge Asymmetry in B+ --> K*0 Rho+ Decays

With a sample of 88.8 BBbar pairs produced at PEP-II in e+e- annihilation through the Upsilon(4S) resonance and recorded with the BABAR detector, we search for the B+ --> K*0 Rho+ decay mode. A signal is observed for the first time with a significance of more than 5 sigma. We measure a preliminary branching fraction of BR(B+ --> K*0 Rho+)=[17.0 +-2.9 (stat) +-2.0 (syst) +0.0 -1.9 (non-resonant)] 10(-6). The "non-resonant" error corresponds to the uncertainty from non-resonant backgrounds not modeled in the fit. The measurement of the longitudinal-polarized component to this vector-vector penguin decay is of special interest. We measure fL= 0.79 +-0.08(stat) +-0.04 (syst) +- 0.02 (non-resonant). We measure the direct-CP-violating charge asymmetry in this mode to be A_CP = -0.14 +- 0.17 +- 0.04.

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arXiv2004

Measurement of the Branching Ratio Gamma(D_s^* -> D_s pi0)/Gamma(D_s^* --> D_s gamma)

The (Delta I = 1) decay D_s^* --> Ds pi0 and (ΔI = 0) decay D_s^* --> Ds gamma have been reconstructed using 90.4 fb^-1 of data recorded by the BaBar detector at the PEP-II asymmetric-energy e^+e^- collider. The relative branching fraction of isospin violating decay to isospin conserving decay has been measured. Our preliminary result for this ratio is Gamma(D_s^* -> D_s pi0)/Gamma(D_s^* --> D_s gamma) = 0.0621 +/- 0.0049 (stat) +/- 0.0063 (syst). In addition we reconstruct the decays D^* --> D0 pi0 and D^* --> D0 gamma for completeness and measure a preliminary relative branching fraction to be Gamma(D^* --> D0 pi0)/Gamma(D&* --> D0 gamma) = = 1.740 +/- 0.020 (stat) +/- 0.125 (syst). Both measurements represent significant improvements over present world averages.

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arXiv2004

A Measurement of CP Violating Asymmetries in B0-->f0(980)K0s Decays

We present preliminary measurements of the CP-violating asymmetries in the decay $B^0\to f_0(980)(\toπ^+π^{-}) K_s^0$. The results are obtained from a data sample of $209\times10^6$ $Υ(4S) \to B\bar{B}$ decays collected with the BaBar detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. From a time-dependent maximum-likelihood fit we measure the mixing-induced CP violation parameter $S=-0.95^{+0.32}_{-0.23} \pm 0.10$ and the direct CP violation parameter $C=-0.24\pm 0.31 \pm 0.15 $, where the first errors are statistical and the second systematic.

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arXiv2004

Evidence For B0 -> rho0 K0S

We present evidence for the decay B0->rho0 K0s. The results are obtained from a data sample of 227 10^6 Y(4S) -> BBbar decays collected with the BABAR detector at the PEP-II asymmetric-energy B-Factory at SLAC. From a maximum-likelihood fit giving a yield of 99+/-19 events and efficiency estimated from simulation we make a preliminary measurement of the branching fraction B0->rho0 K0 =(5.1+/-1.0+/-1.2)10^-6 where the first error is statistical and the second systematic. The hypothesis of zero signal in the rho0 mass region, 600MeV-930MeV, is excluded at the 6.1sigma level. Allowing a B0->f_0(600)K0s contribution in the fit allows us to exclude the hypothesis of zero B0->rho0 K0s at the 3.5sigma level.

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