arXiv subjects

BABAR Collaboration

Publications and source records attributed to BABAR Collaboration.

At least 91 records · Page 5Linked to original sources

arXiv2004

Measurement of the B0bar Lifetime and of the B0-B0bar Oscillation Frequency Using Partially Reconstructed B0bar -> D*+ l- anti-nu(l) Decays

We present a simultaneous measurement of the B0bar lifetime tau(B0) and mixing parameter $Delta m_d$. We use a sample of about 50000 B0bar -> D*+ l- anti-nu(l) partially reconstructed decays identified with the BABAR detector at the PEP-II storage ring at SLAC, where the flavor of the other B meson is determined from the charge of another high momentum lepton in the same event. The preliminary results are: tau(B0) = (1.501+/-0.008(stat.) +/- 0.030 (syst.)) ps, $Delta m_d$ = (0.523+/-0.004(stat.) +/- 0.007 (syst.)) ps^{-1}.

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arXiv2004

Partial Reconstruction of $B^0\to D_s^{\ast+} D^{\ast-}$ Decays and Measurement of the $D_s^+\toϕπ^+$ Branching Fraction

We present preliminary results on the branching fractions $BF(B^0\to D_s^{\ast+} D^{\ast-})$ and $BF(D_s^+\toϕπ^+)$, based on a data sample of approximately $124\times10^6$ \BB events collected by the \babar detector at the PEP-II $e^+ e^-$ \B--factory. $BF(B^0\to D_s^{\ast+} D^{\ast-})$ is measured selecting neutral \B meson decays to the final state $D_s^{\ast+} D^{\ast-}$ with partial reconstruction of the $D_s^{\ast+}$, in which only the $D^{\ast-}$ and the soft photons from the decay $D_s^{\ast+} \to D_s^+ γ$ are reconstructed. The branching fraction product $BF(B^0\to D_s^{\ast+} D^{\ast-}) \cdot BF(D_s^+\toϕπ^+)$ is measured via a complete reconstruction of the whole decay chain. Comparing these two measurements provides a model-independent determination of the $BF(D_s^+\toϕπ^+)$ branching fraction. We obtain the following preliminary results: $BF(B^0\to D_s^{\ast+} D^{\ast-}) = (1.85 \pm 0.09 \pm 0.16)%$, $BF(D_s^+\toϕπ^+) = (4.71 \pm 0.47 \pm 0.35)%$ where the first error in each measurement is statistical, the second systematic.

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arXiv2004

Amplitude Analysis of B -> pi pi pi and B -> K pi pi

We present preliminary results of a maximum-likelihood Dalitz-plot analysis of the charmless hadronic B decays to the final states pi pi pi and K pi pi from data corresponding to an integrated on-resonance luminosity of 166 fb^-1 recorded by the BABAR experiment at the SLAC PEP-II asymmetric-energy B Factory. We measure the total branching fractions B(B -> pi pi pi) = (16.2 +- 2.1 +- 1.3) x 10^-6 and B(B -> K pi pi) = (61.4 +- 2.4 +- 4.5) x 10^-6, and provide fit fractions and phases for intermediate resonance states.

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arXiv2004

Search for B --> chi_c K(*) decays

We report on the search for the factorization suppressed decays B -> chi_c0 K(*) and B -> chi_c2 K(*), with chi_c0 and chi_c2 decaying into J/psi gamma. We use a sample of 124 million BBbar events collected with the BABAR detector at the PEP-II storage ring at the Stanford Linear Accelerator Center. No significant signal is found and upper bounds for the branching fractions are obtained. All results are preliminary.

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arXiv2004

Measurement of exclusive B decays to charmonium and K or K* branching fractions with the BABAR detector

We report preliminary results on the measurement of branching fractions of exclusive decays of neutral and charged B mesons into two-body final states containing a charmonium state and a light strange meson. The charmonium mesons considered are J/psi, psi(2S) and chic_c1, and the light mesons are either K or K*. We use a sample of about 124 million BBbar events collected with the BABAR detector at the PEP-II storage ring at the Stanford Linear Accelerator Center.

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arXiv2004

A Search for the Theta^*++ Pentaquark in B+ -> p pbar K+

We report the results of a search for the Theta*++ pentaquark in the decay B+ -> Theta*++ pbar where Theta*++ -> pK+ using 81fb^-1 of data collected on the Upsilon(4S) resonance with the BaBar detector at PEP-II. We find an upper limit on the branching fraction of B+ -> Theta*++ pbar where Theta*++ -> pK+ to be 1.5x10^-7 for 1.43<m(Theta*++)<1.85GeV/c^2, 2.4x10^-7 for 1.85<m(Theta*++)<2.00GeV/c^2 and 3.3x10^-7 for 2.00<m(Theta*++)<2.36GeV/c^2, at 90% confidence level. All results are preliminary.

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arXiv2004

Limits on the Decay-Rate Difference of Neutral-B Mesons and on CP, T, and CPT Violation in B0-antiB0 Oscillations

Using events in which one of two neutral-B mesons from the decay of an Y(4S) resonance is fully reconstructed, we set limits on the difference between the decay rates of the two neutral-B mass eigenstates and on CP, T, and CPT violation in B0-antiB0 mixing. The reconstructed decays, comprising both CP and flavor eigenstates, are obtained from 88 million Y(4S) --> Banti-B decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We determine six independent parameters governing oscillations (Deltam, DeltaGamma/Gamma), CPT and CP violation (Re Z, Im Z), and CP and T violation (Im lambdaCP, |q/p|), where lambdaCP characterizes B0 and anti-B0 decays to states of charmonium plus K0S or K0L. The results are sgn(Re lambdaCP)xDeltaGamma/Gamma = -0.008 +/- 0.037(stat) +/- 0.018(syst) [-0.084,0.068], |q/p| = 1.029 +/- 0.013(stat) +/- 0.011(syst) [ 1.001,1.057], (Re lambdaCP)/|lambdaCP|xRe z = 0.014 +/- 0.035(stat) +/- 0.034(syst) [-0.072,0.101], Im z = 0.038 +/- 0.029(stat) +/- 0.025(syst) [-0.028,0.104], The values inside square brackets indicate the 90% confidence-level intervals. The values of Im lambdaCP and Deltam are consistent with previous analyses and are used as cross-checks. These measurements are in agreement with Standard Model expectations.

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arXiv2004

Measurements of $Λ^+_c$ Branching Fractions of Cabibbo-Suppressed Decay Modes

We have measured the branching fractions of the Cabibbo-suppressed decays $Λ^+_c$ $\to$ $Λ^{0}$ $K^+$ and $Λ^+_c$ $\to$ $Σ^0$ $K^+$ %(measured with improved accuracy). relative to the Cabibbo-allowed decay modes $Λ^+_c$ $\to$ $Λ^{0}$ $π^+$ and $Λ^+_c$ $\to$ $Σ^0$ $π^+$ to be $ 0.044 \pm 0.004 (\textnormal{stat.}) \pm 0.002 (\textnormal{syst.})$ and $ 0.040 \pm 0.005 (\textnormal{stat.}) \pm 0.004 (\textnormal{syst.})$, respectively. We also present the first observation of $Λ^+_c$ $\to$ $Λ^{0}$ $K^+ π^+ π^-$ and have measured the branching fraction relative to $Λ^+_c$ $\to$ $Λ^{0}$ $π^+$ to be $0.266 \pm 0.027 (\textnormal{stat.}) \pm 0.032 (\textnormal{syst.})$. The upper limit of the branching fraction into the decay $Λ^+_c$ $\to$ $Σ^0$ $K^+ π^+ π^-$ relative to $Λ^+_c$ $\to$ $Σ^0$ $π^+$ has been measured to be %7.6 \times 10^{-4}$ $ < 3.9 \times 10^{-2}$ at the 90% confidence level. This analysis was performed using a data sample of %approximately 125 fb$^{-1}$ (integrated luminosity) collected by the \babar$ $detector at the PEP-II asymmetric-energy $B$ Factory at the Stanford Linear Accelerator Center. All results presented in this conference contribution are preliminary.

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arXiv2004

Measurement of the B0bar --> D*+ l- nubar_l Decay Rate and |Vcb|

We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb| based on a sample of about 53,700 B0bar --> D*+ l- nubar_l decays observed by the BaBar detector. We obtain the branching fraction averaged over l = e, mu, BR(B0bar --> D*+ l- nubar_l) = (4.90 +- 0.07(stat.) +0.36-0.35(syst.))%. We measure the differential decay rate as a function of w, the relativistic boost gamma of the D*+ in the B0bar rest frame. By extrapolating dGamma/dw to the kinematic limit w --> 1, we extract the product of |Vcb| and the axial form factor A_1(w=1). We combine this measurement with a lattice QCD calculation of A_1(w=1) to determine |Vcb| = (38.7 +- 0.3(stat.) +- 1.7(syst.) +1.5-1.3(theory)) * 10^-3.

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arXiv2004

Search for the Rare Leptonic Decay B- -> tau- nubar

We present a search for the decay $B^{-} \to τ^{-} \barν_τ$ in a sample of $88.9 \times 10^{6}$ $B\bar{B}$ pairs recorded with the BaBar detector at the SLAC $B$-Factory. One of the two $B$ mesons from the $Υ(4S)$ is reconstructed in a hadronic or a semileptonic final state and the decay products of the other $B$ in the event are analyzed for consistency with a $B^{-} \to τ^{-} \barν_τ$ decay. We find no evidence of a signal and set an upper limit on the branching fraction of $\mathcal{B}(B^{-} \to τ^{-} \barν_τ) < 4.2 \times 10^{-4}$ at the 90% confidence level.

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arXiv2004

Measurements of the Branching Fraction and CP-Violation Asymmetries in B^0-->f0(980)Ks

We present measurements of the branching fraction and CP-violating asymmetries in the decay $B^0 \to f_0(980)K^0_S$. The results are obtained from a data sample of $123\times10^6$ $Υ(4S) \to B\bar{B}$ decays. From a time-dependent maximum likelihood fit we measure the branching fraction ${\cal B}(\Bz\to f_0(980)(\toπ^+π^-)K^0)=(6.0\pm0.9\pm0.6\pm1.2)\times 10^{-6}$, the mixing-induced CP violation parameter $S=-1.62^{+0.56}_{-0.51} \pm 0.09\pm 0.04$ and the direct CP violation parameter $C=0.27\pm 0.36\pm 0.10 \pm 0.07 $, where the first errors are statistical, the second systematic and the third due to model uncertainties. We measure the $f_0(980)$ mass and width to be $m_{f_0(980)}=(980.6 \pm 4.1 \pm 0.5\pm 4.0){\rm MeV}/c^2$ and $Γ_{f_0(980)}=(43^{+12}_{-9} \pm 3 \pm 9){\rm MeV}/c^2$, respectively.

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arXiv2004

Measurement of Time-dependent CP-violating Asymmetries in B0 -> K0 gamma (K0 -> K0_S pi0) Decays

We present a measurement of the time-dependent CP-violating asymmetries in $B^0 \to K^{*0}γ(K^{*0}\to K_S^0 π^0)$ decays based on 124 million $Υ(4S)\to B^0\bar{B}^0$ decays collected with the BaBar detector at the PEP-II asymmetric-energy $B$ Factory at the Stanford Linear Accelerator Center. In a sample containing $105\pm 14$ signal decays, we measure $S_{K^{*0}} = 0.25 \pm 0.63 \pm 0.14$ and $S_{K^{*0}} = -0.57 \pm 0.32 \pm 0.09$, where the first error is statistical and the second systematic.

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arXiv2004

Search for B0 Decays to Invisible Final States and to nu nubar gamma

We establish upper limits on branching fractions for B0 decays to final states where the decay products are purely invisible (i.e., no observable final state particles) and for B0 decays to nu nubar gamma. Within the Standard Model, these decays have branching fractions that are below current experimental sensitivity, but various models of physics beyond the Standard Model predict significant contributions from these channels. Using 88.5 million B Bbar pairs collected at the Y(4S) resonance by the BaBar experiment at the PEP-II e+e- storage ring at the Stanford Linear Accelerator Center, we establish upper limits at the 90% confidence level of 22 x 10^-5 for the branching fraction of B0 -> invisible and 4.7 x 10^-5 for the branching fraction of B0 -> nu nubar gamma.

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arXiv2004

Determination of the Branching Fraction for B --> Xc l nu Decays and of |Vcb| from Hadronic-Mass and Lepton-Energy Moments

We determine the inclusive B --> Xc l nu branching fraction, the CKM matrix element |Vcb|, and other heavy-quark parameters from a simultaneous fit to moments of the hadronic-mass and lepton-energy distributions in semileptonic B-meson decays, measured as a function of the lower limit on the lepton energy, using data recorded with the BABAR detector. Using Heavy Quark Expansions (HQEs) to order 1/mb^3, we extract BR_cenu=(10.61 +- 0.16(exp) +- 0.06(HQE))% and |Vcb| = (41.4 +- 0.4(exp) +- 0.4(HQE) +- 0.6(th)) 10^-3. The stated errors refer to the experimental, HQE, and additional theoretical uncertainties.

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arXiv2004

Measurement of the Ratio of Decay Amplitudes for B0bar -> J/psi K0 and B0 -> J/psi K0

We have measured the time-dependent decay rate for the process $B \to J/ψK^{*0}(892)$ in a sample of about 88 million $Υ(4S) \to B\bar{B}$ decays collected with the BaBar detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. In this sample we study flavor-tagged events in which one neutral $B$ meson is reconstructed in the $J/ψK^{*0}$ or $J/ψ\bar{K}^{*0}$ final state. We measure the coefficients of the cosine and sine terms in the time-dependent asymmetries for $J/ψK^{*0}$ and $J/ψ\bar{K}^{*0}$, find them to be consistent with the Standard Model expectations, and set upper limits at 90% C.L. on the decay amplitude ratios $|A (\bar{B}^0 \to J/ψK^{*0})|/|A (B^0 \to J/ψK^{*0})| < 0.26$ and $|A (B^0 \to J/ψ\bar{K}^{*0})|/|A (\bar{B}^0 \to J/ψ\bar{K}^{*0})| <0.32$. For a single ratio of wrong-flavor to favored amplitudes for $B^0$ and $\bar{B}^0$ combined, we obtain an upper limit of 0.25 at 90% C.L.

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arXiv2004

Measurement of the Direct CP Asymmetry in b -> s gamma Decays

We describe a measurement of the direct CP asymmetry between inclusive b -> s gamma and bbar -> sbar gamma decays. This asymmetry is expected to be less than 0.01 in the Standard Model, but could be enhanced up to about 0.10 by new physics contributions. We use a sample of 89 million BB pairs recorded with the BaBar detector at PEP-II, from which we reconstruct a set of 12 exclusive b -> s gamma final states containing one charged or neutral kaon and one to three pions. We measure an asymmetry of A_CP(b -> s gamma) = 0.025 +/- 0.050(stat.) +/- 0.015(syst.), corresponding to an allowed range of -0.06 < A_CP(b -> s gamma) < +0.11 at 90% confidence level.

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arXiv2004

Measurement of the Time-Dependent CP Asymmetry in the B0 --> Phi K0 Decay

We present a measurement of the time-dependent CP asymmetry for the neutral B-meson decay B0 --> Phi K0. We use a sample of approximately 114 million B-meson pairs taken at the Upsilon(4S) resonance with the BaBar detector at the PEP-II B-meson Factory at SLAC. We reconstruct the CP eigenstates Phi K0_S and Phi K0_L where Phi --> K+ K-, K0_S --> pi+ pi-, and K0_L is observed via its hadronic interactions. The other B meson in the event is tagged as either a B0 or B0-bar from its decay products. The values of the CP-violation parameters are S = 0.47 +/- 0.34 (stat) +0.08/-0.06 (syst) and C = 0.01 +/- 0.33 (stat) +/- 0.10 (syst).

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arXiv2004

Measurement of the B^+/B^0 Production Ratio from the Upsilon(4S) Meson using B^+ -> J/psi K^+ and B^0 -> J/psi K^{0}_{S} Decays

We report a measurement of the production ratio of charged and neutral B mesons from Upsilon(4S) decays based on the ratio of efficiency-corrected yields for the charmonium modes J/psi K^+ and J/psi K^{0}_{S} with 81.9 fb^-1 of data collected with the BABAR detector on the Upsilon(4S) resonance at 10.580 GeV. We find a value of 1.006 +/- 0.036 (stat) +/- 0.031 (sys) for the ratio R^{+/0}=Gamma(Upsilon(4S) -> B^+ B^-)/Gamma(Upsilon(4S)->B^0 B^0bar).

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