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The BABAR Collaboration

Publications and source records attributed to The BABAR Collaboration.

At least 523 records · Page 29Linked to original sources

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

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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arXiv2002

Measurement of the Inclusive Electron Spectrum in Charmless Semileptonic B Decays Near the Kinematic Endpoint

A preliminary result on the study of the inclusive electron spectrum in B -> X_u e nu decays above the kinematic limit for the dominant B -> X_c e nu transitions is presented. This study is performed at the PEP-II asymmetric B Factory, where B meson pairs are produced in the decay of the Upsilon(4S) resonance. For the electron momentum range of 2.3 - 2.6 GeV/c in the Upsilon(4S) rest frame, the partial branching ratio is measured to be Delta B(B -> X_u e nu)=(0.152+-0.014+-0.014) 10^{-3}.

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arXiv2002

Search for Decays of B0 Mesons into Pairs of Leptons

We present a search for the decays B0->e+e-, B0->mu+mu-, and B0->emu in data collected at the Upsilon(4S) with the BABAR detector at the SLAC B Factory. Using a data set of 54.4 fb-1, we find no evidence for a signal and set the following preliminary upper limits at the 90% confidence level: B(B0->e+e-)< 3.3*10E-7, B(B0->mu+mu-) < 2.0*10E-7, and B(B0->emu) < 2.1*10E-7.

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arXiv2002

Measurement of the First Hadronic Spectral Moment from Semileptonic B Decays

A preliminary determination of the first moment of the hadronic mass distribution <(M_X)^2 - bar{m_D}^2> in semileptonic B decays has been obtained as a function of the minimum lepton momentum, ranging from 0.9 to 1.6 GeV/c. The measurement is based on a new technique involving BBbar events in which one fully reconstructed B meson decays hadronically and the recoiling B decays semileptonically. The mass of the hadrons in the semileptonic decay is determined from a kinematic fit to the whole event. For different minimum lepton momenta, the mass distribution is decomposed into contributions from various charm resonant states and a non-resonant contribution, allowing for the determination of the first moment. From these moments the Heavy Quark Effective Theory (HQET) parameters lambda_1 and Lambdabar can be derived. For lepton momenta in the B rest frame above 1.5 GeV/c, we find a first moment that is compatible with existing measurements. However, if we extend the measurement to lower values of lepton momenta, the data can only be described by Operator Product Expansion calculations if we use significantly different values for Lambdabar and lambda_1 than obtained from earlier measurements based on lepton momentum spectra and the photon spectrum in b --> s gamma transitions.

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arXiv2002

A Search for the Decay B0 -> pi0 pi0

We present a search for the decay B^0 --> pi^0 pi^0 by the BABAR experiment at the PEP-II asymmetric-energy B-factory at SLAC. Using approximately 88 million B bar{B} pairs collected between 1999 and 2002, we place a 90% confidence level upper limit on the branching fraction of B(B^0 --> pi^0 pi^0) < 3.6 times 10^{-6}. This result is preliminary.

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arXiv2002

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

We measure the B0 lifetime tau_B0 and the B-Bbar oscillation frequency Deltam_d with a sample of approximately 14,000 exclusively reconstructed B0 -> D*- l+ nu_l signal events, selected from 23 million B-Bbar pairs recorded at the Upsilon(4S) resonance with the BABAR detector at the Stanford Linear Accelerator Center. The b-quark flavor of the other B at the time of decay and its decay position are determined inclusively. The lifetime and oscillation frequency are measured simultaneously with an unbinned maximum-likelihood fit that uses, for each event, the measured difference in B decay times (Delta-t), the calculated uncertainty on Delta-t, the signal and background probabilities, and b-quark tagging information for the other B. The preliminary results are tau_B0 = (1.523 +0.024 -0.023 (stat) +/- 0.022 (syst)) ps and Deltam_d = (0.492 +/- 0.018 (stat) +/- 0.013 (syst)) ps^-1. The statistical correlation coefficient between tau_B0 and Deltam_d is -0.22.

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arXiv2002

Measurement of Time-Dependent CP Asymmetries and the CP-odd Fraction in the Decay B^0 --> D^{+}D^{-}

We present a measurement of time-dependent CP asymmetries and an updated determination of the CP-odd fraction in the decay B^0 --> D^{*+}D^{*-}. The measurements are derived from a data sample of 88 times 10^{6} B bar{B} pairs collected by the BaBar detector at the PEP-II energy asymmetric B Factory at SLAC. All results are preliminary.

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arXiv2002

Search for the Exclusive Radiative Decays B -> rho gamma and B -> omega gamma

A search for the exclusive radiative decays B->rho(770) gamma and B^0->omega(782) gamma is performed on a sample of 84 million BB-bar events collected by the BABAR detector at the PEP-II asymmetric e^+e^- collider. No significant signal is seen in any of the channels. We set preliminary upper limits of BR[B^0->rho^0 gamma]< 1.4 times 10^{-6}, BR[B^+ -> rho^+ gamma] < 2.3 times 10^{-6} and BR[B^0 -> omega gamma]< 1.2 times 10^{-6} at 90% Confidence Level. Combining these into a single limit on the generic process B-> rho gamma, we find the preliminary limit BR[B -> rho gamma]<1.9 times 10^{-6}, corresponding to a limit of BR[B -> rho gamma]/BR[B-> K* gamma] < 0.047 at 90% Confidence Level.

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arXiv2002

b --> s gamma using a Sum of Exclusive Modes

This paper describes preliminary results on the inclusive process b --> s gamma obtained from 20.7 fb^-1 of data recorded with the BaBar detector during 1999-2000. Signal event yields are found from a combination of twelve exclusive decay channels after subtracting continuum and BBbar backgrounds. Cross-feed from incorrectly reconstructed b --> s gamma events is also removed. Branching fractions in bins of hadronic mass are calculated using corrected Monte Carlo signal efficiencies; this is equivalent to measuring the gamma energy spectrum. We measure the first moment of the gamma energy spectrum constraining the HQET parameter LambdaBar = (0.37 +/- 0.09 (stat) +/- 0.07 (syst) +/- 0.10 (model)) GeV/c^2. A fit to the hadronic mass spectrum gives B(b --> s gamma) = (4.3 +/- 0.5 (stat) +/- 0.8 (syst) +/- 1.3 (model))x 10^-4 for the inclusive branching fraction. We also constrain the HQET parameter lambda_1.

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arXiv2002

A Study of The Rare Decays B0 -> Ds()+ pi- and B0 -> Ds()-K+

We report on the evidence for the decays B0 -> Ds+ pi- and B0 -> Ds- K+ and the results of a search for the decays B0 -> Ds*+ pi- and B0 -> Ds*-K+ from a sample of 84 million Upsilon(4S) decays into B meson pairs collected with the BABAR detector at the PEP II asymmetric-energy e^{+}e^{-} collider. The measured B0 -> Ds+ pi- yield has a probability of less than 10^{-3} to be a fluctuation of the background and we measure the branching fraction Br(B0 -> Ds+ pi-) = (3.2 +- 0.9 (stat) +- 1.0 (syst)) x 10^-5. The measured B0 -> Ds- K+ yield has a probability of less than 5 times 10^{-4} to be a fluctuation of the background and we measure the branching fraction Br(B0 -> Ds- K+) = (3.2 +- 1.0 (stat) +- 1.0 (syst)) x 10^-5. We also set 90% C.L. limits Br(B0 -> Ds*+ pi-)< 4.1 x 10^-5 and Br(B0 -> Ds*- K+) < 2.5 x 10^-5. All results are preliminary

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arXiv2002

Measurements of the branching fractions of charmless three-body charged B decays

We present preliminary results of searches for charged B mesons decaying into the charmless three-body final states hhh, where h = pi or K, using 51.5 fb^-1 of data collected at the Upsilon(4S) resonance with the BABAR detector at the SLAC PEP-II asymmetric B Factory. No assumptions are made about intermediate resonances. We measure the branching fractions B(B+ -> K+ pi- pi+) = (59.2 +- 4.7 +- 4.9) x 10^-6 and B(B+ -> K+ K- K+) = (34.7 +- 2.0 +- 1.8) x 10^-6, where the first error is statistical and the second error is systematic. In the same study, we do not observe significant signals for the final states B+ -> pi+ pi- pi+ and B+ -> K+ K- pi+, and therefore provide the 90% confidence upper limits B(B+ -> pi+ pi- pi+) < 15 x 10^-6 and B(B+ -> K+ K- pi+) < 7 x 10^-6.

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arXiv2002

Evidence for the $b\to u$ Transition $B^0\to D_s^+ pi^-$ and a Search for $B^0\to D_s^*+ pi^-$

We report evidence for the $b\to u$ transition $B^0 \to D_s^{+}π^-$ and the results of a search for $B^0 \to D_s^{*+} π^-$ from a sample of $61.6\times 10^6$ $Y(4S)$ decays into $B$ meson pairs collected with the BaBar detector at the PEP II asymmetric $e^{+}e^{-}$ collider. The observed $B^0 \to D_s^{+} π^-$ yield has a probability of $4.4 \times 10^{-4}$ to be a fluctuation of the background (3.5 $σ$) and we measure the branching fraction $B^0 \to D_s^{+} π^-=3.1 \pm 1.0 ({\rm stat.})\pm 1.0 ({\rm syst.})$. We also set a limit $B^0 \to D_s^{*+} π^- <~4.3\times 10^{-5}$ at 90% C.L.

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arXiv2002

Branching Fraction Measurements of the Decays B -> EtaC K, where EtaC -> KKbarPi and EtaC -> 4K

In this report, we present the observation of the exclusive decays B0 -> EtaC K0 and B+ -> EtaC K+, and the measurement of the related branching fractions. Using a sample of 22.7x10^6 Upsilon(4S) -> BBbar decays collected with the BABAR detector at the SLAC PEP-II asymmetric B Factory during 1999-2000, we have observed statistically significant signals in the EtaC -> KsK+Pi- and K+K-Pi0 channels and set upper limits in the EtaC -> K+K-K+K- channels. All the results presented are preliminary. We have measured BF(B+ -> EtaC K+) = (1.50 +/- 0.19 +/- 0.15 +/- 0.46)x10^{-3} BF(B0 -> Etac K0) = (1.06 +/- 0.28 +/- 0.11 +/- 0.33)x10^{-3} where the first error is statistical, the second systematic and the last due to the uncertainty on the world average EtaC -> KKbarPi branching fraction.

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arXiv2002

A Measurement of the Neutral B Meson Lifetime using Partially Reconstructed B0 --> D*-pi+ Decays

The neutral B meson lifetime has been measured with the data collected by the BABAR detector at the PEP-II storage ring during the year 2000 for a total integrated luminosity of 20.3 fb-1. The B0 --> D*- pi+ decays have been selected with a partial reconstruction method in which only the fast pion from the B0 decay and the slow pion from D*- --> D0 bar pi- are reconstructed. The B0 lifetime has been measured to be 1.510 +/- 0.040 +/- 0.038 ps with a sample of 6971 +/- 241 reconstructed signal events.

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arXiv2002

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

We present a preliminary 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 by the BaBar detector at the PEP-II $e^+e^-$ collider. The result of this analysis is $\mathcal{B}(B^0\to J/ψπ^+π^-$) = (5.0 $\pm$ 0.7 $\pm$ 0.6)$\times 10^{-5}$, where the first error is statistical and the second is systematic.

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arXiv2002

Rare B Decays to States Containing a J/psi Meson

We report preliminary measurements of the branching fractions for B+ -> J/psi phi K+, B0 -> J/psi phi K0S, B0 -> J/psi phi, B0 -> J/psi eta and B -> J/psi eta' using 56 million BBbar events collected at the Y(4S) resonance with the BABAR detector at PEP-II. We measure branching fractions of B(B+ -> J/psi phi K+)=(4.4+-1.4(stat)+-0.7(syst))*10^-5 and B(B0 -> J/psi phi K0S)=(5.1+-1.9(stat)+-0.9(syst))*10^-5, and set upper limits at 90% C.L. for branching fractions, B(B -> J/ψphi)< 0.95*10^-5, B(B -> J/ψeta)< 2.7*10^-5, and B(B -> J/ψeta')< 6.4*10^-5.

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arXiv2002

Measurement of the B0 Lifetime with Partial Reconstruction of B0bar -> D*+ rho-

A sample of about 5500 $\bar B^0 \to D^{*+} ρ^-$ and 700 $\bar B^0 \to D^{*+} a_1^-$ events is identified, using the technique of partial reconstruction, among 22.7 $B\bar B$ pairs collected by the BaBar experiment at the PEP-II storage ring. With these events, the $B^0$ lifetime is measured to be $1.616 \pm 0.064 \pm 0.075$ ps. This measurement serves as validation for the procedures required to measure $\sin(2β+ γ)$ with partial reconstruction of $\bar B^0 \to D^{*+} ρ^-$.

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