arXiv subjects

B. Aubert

Publications and source records attributed to B. Aubert.

At least 559 records · Page 31Linked to original sources

arXiv2003

Measurements of Branching Fractions and CP-violating Asymmetries in B0->pi+ pi-, K+ pi-, K+ K- Decays

We present measurements of branching fractions and CP-violating asymmetries for neutral B meson decays to two-body final states of charged pions and kaons based on a sample of about 88 million Y(4S)-->BB decays. From a time-independent fit we measure the charge-averaged branching fractions B(B0-->pi+pi-) = (4.7 +/- 0.6 +/- 0.2) x 10^-6, B(B0-->K+pi-) = (17.9 +/- 0.9 +/- 0.7) x 10^-6, and the direct CP-violating charge asymmetry A(Kpi) = -0.102 +/- 0.050 +/- 0.016; [-0.188,-0.016], where the ranges in square brackets indicate the 90% confidence intervals. From a time-dependent fit we measure the B0-->pi+pi- CP-violating parameters Spipi = 0.02 +/- 0.34 +/- 0.05; [-0.54,+0.58] and Cpipi = -0.30 +/- 0.25 +/- 0.04; [-0.72,+0.12].

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arXiv2003

Study of semi-inclusive production of eta' mesons in B decays

We report a measurement of the rate for $B \to η' X_s$ transitions where the $η'$ meson has center-of-mass momentum in the range 2.0 to 2.7\gevc and $X_s$ represents a system comprising a kaon and up to four pions. Our study is based on 22.2 million $B\bar{B}$ pairs collected at the $Υ(4S)$ with the BABAR detector at the Stanford Linear Accelerator Center. We find $\mathcal{B}(B \to η' X_s)=(6.8^{+0.7}_{-1.7}(stat)\pm1.0(syst)^{+0.0}_{-0.5}(bkg))\times10^{-4}$ assuming that the signal is due to $b \to sg^*$ transitions.

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arXiv2003

Measurement of the branching fractions for psi(2S)-->e+e- and psi(2S)-->mu+mu-

We measure the branching fractions of the psi(2S) meson to the leptonic final states e+e- and mu+mu- relative to that for psi(2S)-->J/psi pi+pi-. The method uses psi(2S) mesons produced in the decay of B mesons at the Upsilon(4S) resonance in a data sample collected with the BABAR detector at the Stanford Linear Accelerator Center. Using previous measurements for the psi(2S)-->J/psi pi+pi- branching fraction, we determine the e+e- and mu+mu- branching fractions to be 0.0078+/-0.0009+/-0.0008 and 0.0067+/-0.0008+/-0.0007 respectively.

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arXiv2003

Study of Inclusive Production of Charmonium Mesons in B Decay

The inclusive production of charmonium mesons in B meson decay has been studied in a 20.3 fb$^{-1}$ data set collected by the BaBar experiment operating at the $Υ(4S)$ resonance. Branching fractions have been measured for the inclusive production of the charmonium mesons $J/ψ$, $ψ(2S)$, $χ_{c1}$, and $χ_{c2}$. The branching fractions are also presented as a function of the center-of-mass momentum of the mesons and of the helicity of the $J/ψ$.

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arXiv2003

Measurement of $J/ψ$ production in continuum $e^+e^-$ annihilations near $\sqrt s = 10.6$ GeV

The production of $J/ψ$ mesons in continuum $e^+e^-$ annihilations has been studied with the BABAR detector at energies near the $Υ(4S)$ resonance, approximately 10.6 GeV. The mesons are distinguished from $J/ψ$ production in B decays through their center-of-mass momentum and energy. We measure the cross section $e^+e^-\to J/ψX$ to be $2.52\pm 0.21\pm 0.21$ pb; for momentum above 2 GeV/c, it is $1.87\pm 0.10\pm 0.15$ pb. We set a 90% confidence level upper limit on the branching fraction for direct $Υ(4S)$\to J/ψX$ decays at $4.7\times 10^{-4}$.

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arXiv2003

Measurement of the CKM Matrix Element |Vub| with B->rho e nu Decays

We present a measurement of the branching fraction for the rare decays B->rho e nu and extract a value for the magnitude of Vub, one of the smallest elements of the Cabibbo-Kobayashi-Maskawa quark-mixing matrix. The results are given for five different calculations of form factors used to parametrize the hadronic current in semileptonic decays. Using a sample of 55 million BBbar meson pairs recorded with the BABAR detector at the PEP-II e+e- storage ring, we obtain Br(B0->rho- e+ nu)=(3.29 +-0.42 +-0.47 +-0.60) x 10^-4 and |Vub|=(3.64 +-0.22 +-0.25 +0.39-0.56)x10^-3, where the uncertainties are statistical, systematic, and theoretical, respectively.

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arXiv2002

Simultaneous Measurement of the B0 Meson Lifetime and Mixing Frequency with B0 --> D*- l+ nu Decays

We measure the B0 lifetime τ_{B0} and the B0-B0bar oscillation frequency Δm_d with a sample of approximately 14,000 exclusively reconstructed B0 --> D*- l+ nu signal events, selected from 23 million BBbar pairs recorded at the Υ(4S) resonance with the BABAR detector at the Stanford Linear Accelerator Center. The decay position of the other B is determined with the remaining tracks in the event, and its b-quark flavor at the time of decay is determined with a tagging algorithm that exploits the correlation between the flavor of the b-quark and the charges of its decay products. The lifetime and oscillation frequency are measured simultaneously with an unbinned maximum-likelihood fit that uses, for each event, the measured difference in decay times of the two B mesons (Δt), the calculated uncertainty on Δt, the signal and background probabilities, and b-quark tagging information for the other B. The results are τ_{B^0} = (1.523^{+0.024}_{-0.023} \pm 0.022) \rm{ps} and Δm_d = (0.492 \pm 0.018 \pm 0.013) \rm{ps}^{-1}. The statistical correlation coefficient between τ_{B0} and Δm_d is -0.22.

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arXiv2002

Measurement of the B0 meson lifetime with partial reconstruction of B0 --> D- pi+ and B0 --> D- rho+ decays

The neutral $B$ meson lifetime is measured with the data collected by the BaBar detector at the PEP-II storage ring during the years 1999 and 2000, with a total integrated luminosity of 20.7 ${\rm fb}^{-1}$. The decays $B^0 \to D^{*-} π^+$ and $B^0 \to D^{*-} ρ^+$ are selected with a partial-reconstruction technique, yielding samples of $6970 \pm 240$ and $5520 \pm 250$ signal events, respectively. With these events, the $B^0 $ lifetime is measured to be $ 1.533 \pm 0.034 {\rm (stat.)} \pm 0.038 {\rm (syst.)} {\rm ps}$. This measurement serves as a test and validation of procedures required to measure the CP violation parameter $\sin(2β+ γ)$ with partial reconstruction of these modes.

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arXiv2002

A Study of the Rare Decays $B^0\to D_s^{()+} π^-$ and $B^0\to D_s^{()-} K^+$

We report evidence for the decays $B^0\to D_s^{+} π^-$ and $B^0\to D_s^{-} K^+$ and the results of a search for $B^0 \to D_s^{*+} π^-$ and $B^0\to D_s^{*-} K^+$ in a sample of 84 milion Y(4S) decays into $B\bar{B}$ pairs collected with the BaBar detector at the PEP II asymmetric-energy $e^{+}e^{-}$ storage ring. We measure the branching fraction Br($B^0 \to D_s^{+} π^-) = 3.2 \pm 0.9 ({\rm stat.})\pm 1.0 ({\rm syst.})$. and Br($B^0 \to D_s^{+} π^-) = 3.2 \pm 1.0 ({\rm stat.})\pm 1.0 ({\rm syst.})$. We also set 90% C.L. limits BR($B^0 \to D_s^{*+} π^-) < 4.1\times 10^{-5}$ at 90% C.L and BR($B^0 \to D_s^{*-} K^+)< 2.5\times 10^{-5}$ at 90% C.L.

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arXiv2002

Measurement of the CP-Violating Asymmetry Amplitude sin2beta

We present results on time-dependent CP-violating asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 88 million Y(4S) --> B Bbar decays collected between 1999 and 2002 with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We study 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. The amplitude of the CP-violating asymmetry, which in the Standard Model is proportional to sin2beta, is derived from the decay-time distributions in such events. We measure sin2beta = 0.741 +/- 0.067 (stat) +/- 0.034 (syst) and |lambda| = 0.948 +/- 0.051 (stat) +/- 0.030 (syst). The magnitude of lambda is consistent with unity, in agreement with the Standard Model expectation of no direct CP violation in these modes.

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arXiv2002

A Measurement of the B0 -> J/psi pi+pi- Branching Fraction

We present a measurement of the branching fraction for the decay of the neutral $B$ meson into the final state $J/ψπ^+π^-$. The data set contains approximately 56 million $B\bar{B}$ pairs produced at the $Υ(4S)$ resonance and recorded with the BaBar detector at the PEP-II asymmetric-energy $e^+e^-$ storage ring. The result of this analysis is $\mathcal{B}$($B^0\to J/ψπ^+π^-$) = (4.6 $\pm$ 0.7 $\pm$ 0.6)$\times 10^{-5}$, where the first error is statistical and the second is systematic. In addition we measure $\mathcal{B}(B^0\to J/ψρ^0) = (1.6 \pm 0.6 \pm 0.4 )\times 10^{-5}$.

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arXiv2002

Measurement of the Branching Fraction for Inclusive Semileptonic B Meson Decays

A largely model-independent measurement of the inclusive electron momentum spectrum and branching fraction for semileptonic decays of B mesons is presented based on data recorded at the Upsilon(4S) resonance with the BABAR detector. Backgrounds from secondary charm decays are separated from prompt B decays using charge and angular correlations between the electron from one B meson and a high momentum electron tag from the second B meson. The resulting branching fraction is BR(B -> X e nu) = (10.87 +-0.18(stat)+-0.30(syst))%. Based on this measurement we determine the CKM matrix element |V_cb|.

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arXiv2002

Measurement of Branching Fractions of Color-Suppressed Decays of the B0bar Meson to D0 pi0, D0 eta, and D0 omega

We report preliminary results of an experimental investigation of the color-suppressed decays bar{B^0} --> D^0 pi^0, D^0 eta, and D^0 omega. We measure the branching fractions B (bar{B^0} --> D^0 pi^0) = (2.89 +/- 0.29 (stat.) +/- 0.38 (syst.)) times 10^{-4}, B (\bar{B^0} \to D^0 η) = (2.41 \pm 0.39 (stat.) +/- 0.32 (syst.)) times 10^{-4}, and B (bar{B^0} --> D^0 omega) = (2.48 +/- 0.40 (stat.) +/- 0.32 (syst.)) times 10^{-4}. The results are based on (48.8 +/- 0.5) times 10^6 B B-bar pairs collected with the BaBar detector. The branching fractions of these color-suppressed decays are significantly larger than theoretical expectations based upon factorization.

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arXiv2002

Measurement of Branching Ratios and CP Asymmetries in B- -> D0(CP)K- Decays

We present preliminary results of the analysis of B -> D0 h decays, with h = pi, K and the D0 reconstructed in the channels K- pi+, K- pi+ pi+ pi-, K- pi+ pi0 and in the CP eigenstate K-K+, using data collected by the BABAR detector during the years 2000-2002 at the PEP-II asymmetric-energy B Factory at SLAC. We have measured the ratio of the branching fractions R = Br(B- -> D0 K-) / Br(B- -> D0 pi-) = (8.31 +- 0.35 (stat) +- 0.20 (syst))% and the direct CP asymmetry A(CP) = (Br(B- -> D0(CP) K-) - Br(B+ -> D0(CP) K+)) / (Br(B- -> D0(CP) K-)+Br(B+ -> D0(CP) K+)) = 0.17 +- 0.23 (stat) +0.09 -0.07 (syst).

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arXiv2002

Dalitz Plot Analysis of D0 Hadronic Decays D0 -> K0K-pi+, D0 -> K0barK+pi- and D0 -> K0barK+K-

A Dalitz plot analysis of the D0 hadronic decays D0 -> K0 K- pi+, D0 -> K0bar K+ pi- and D0 -> K0bar K+ K- is presented. This analysis is based on a data sample of 22 fb-1 collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC running on or near the Y(4S) resonance. The events are selected from continuum e+ e- annihilations using the decay D*+ -> D0 pi+. Preliminary measurements of the branching fractions of the above hadronic decays are obtained. Preliminary estimates of fractions and phases for resonant and nonresonant contributions to the Dalitz plot are also presented.

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arXiv2002

Measurement of the Branching Fractions for the Exclusive Decays of B0 and B+ to Dbar()D()K

Using data collected with the babar detector between 1999 and 2002, we report the observation of 823+-57 B0 and 969+-65 B+ decays to Dbar(*)D^(*)K, where Dbar(*) and D(*) are fully reconstructed and where K is either a K+ or a K0_S decaying to pi+pi-. All 22 possible B decays to Dbar(*)D(*)K are reconstructed exclusively and the corresponding branching fractions or limits are determined. The preliminary branching fractions of the B0 and of the B+ to Dbar(*)D^(*)K are found to be Br(B0->Dbar(*)D^(*)K)=(4.3+-0.3(stat)+-0.6 (syst))10^-2 Br(B+->Dbar(*)D^(*)K)=(3.5+-0.3(stat)+-0.5 (syst))10^-2

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arXiv2002

Determination of the Branching Fraction for Inclusive Decays B -> X_{s} gamma

We present a preliminary determination of the inclusive branching fraction for the rare radiative penguin transition B -> X_{s} gamma. The measurement is based on a data sample of 60 million BB pairs collected between 1999 and 2001 with the BaBar detector at the PEPII asymmetric-energy e+e- B Factory at SLAC. We study events containing a high-energy photon from one B (or Bbar) decay and a tagging primary lepton from the decay of the other B meson. By this means, we are able to reduce a significant component of the background without introduction of model dependent uncertainties in the event selection efficiency. We determine the branching fraction BR(B->X_{s} gamma)=3.88 +-0.36(stat.)+-0.37(sys.) +0.43-0.23(model.)x10^{-4}, which is consistent with Standard Model predictions and provides a constraint on possible new physics contributions to the electromagnetic penguin amplitude in B decays.

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arXiv2002

Measurement of B0->Ds()+D- branching fractions and polarization in the decay B0->Ds+D- with a partial reconstruction technique

We present measurements of the decays B0->Ds(*)+D*-, using data recorded by the BABAR detector in 1999 and 2000, consisting of 20.8 fb^-1. The analysis is conducted with a partial reconstruction technique, in which only the Ds(*)+ and the soft pion from the D*- decay are reconstructed. From the observed rates, we measure the branching fractions BR(B0->Ds+D*-) = (1.03 +- 0.14 +- 0.13 +- 0.26)% and BR(B0->Ds*+D*-) = (1.97 +- 0.15 +- 0.30 +- 0.49)%, where the first error is statistical, the second is systematic, and the third is the error due to the Ds+->phi pi+ branching fraction uncertainty. From the B0->Ds*+D*- angular distributions, we measure the fraction of longitudinal polarization Gamma_L/Gamma = (51.9 +- 5.0 +- 2.8)%, which is consistent with the theoretical prediction, based on factorization. These results are preliminary.

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