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The BABAR Collaboration

Publications and source records attributed to The BABAR Collaboration.

At least 487 records · Page 27Linked to original sources
arXiv2004

Observation of a Narrow Meson Decaying to Ds pi0 gamma at a Mass of 2.458 GeV/c^2

A narrow state, which we label DsJ(2458)+, with mass 2458.0 +/- 1.0(stat.) +/- 1.0(syst.) MeV/c^2, is observed in the inclusive Ds+ pi0 γ$ mass distribution in 91 fb-1 of e^+e^- annihilation data recorded by the BABAR detector at the PEP-II asymmetric-energy e^+e^- storage ring. The observed width is consistent with the experimental resolution. The data favor decay through Ds*(2112)+ pi0 rather than through DsJ*(2317)+ gamma. An analysis of Ds+ pi0 data accounting for the influence of the DsJ(2458)+ produces a DsJ*(2317)+ mass of 2317.3 +/- 0.4(stat.) +/- 0.8(syst.) MeV/c^2.

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arXiv2003

Search for Lepton-Flavor Violation in the Decay $τ^-\to\ell^-\ell^+\ell^-$

A search for the lepton-flavor-violating decay of the tau into three charged leptons has been performed using $91.5 \mathrm{fb}^{-1}$ of data collected at an $e^+e^-$ center-of-mass energy of 10.58 GeV with the BaBar detector at the PEP-II storage ring. In all six 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 $(1-3) \times 10^{-7}$ at 90% confidence level.

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arXiv2003

Observation of the Decay B0 => rho+ rho- and Measurement of the Branching Fraction and Polarization

We have observed the rare decay B0 => rho+ rho- in a sample of 89 million BB pairs recorded with the BABAR detector. The number of observed events is 88 +23-21 +-9, with a significance of 5.1 standard deviations with systematic uncertainties included. The branching fraction and the longitudinal polarization are measured to be BR(B0 => rho+ rho-) = (25 +7-6 +5-6)*10^{-6} and Gamma_L/Gamma = 0.98 +0.02-0.08 +-0.03, respectively.

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arXiv2003

Observation of $B^0\raωK^0$, $B^+\raηπ^+$, and $B^+\raηK^+$ and Study of Related Decays

We present measurements of branching fractions and charge asymmetries for seven B-meson decays with an eta, eta' or omega meson in the final state. The data sample corresponds to 89 million BBbar pairs produced from e+e- annihilation at the Upsilon(4S) resonance. We measure the following branching fractions in units of 10^{-6}: B(etapi+)=5.3+/-1.0+/-0.3, B(etaK+)=3.4+/-0.8+/-0.2, B(etaK0)=2.9+/-1.0+/- 0.2 (<5.2, 90% C.L.), B(eta'pi+=2.7+/-1.2+/-0.3 (<4.5, 90% C.L.), B(omegapi+)=5.5+/-0.9+/-0.5, B(omegaKp)=4.8+/-0.8+/-0.4, and B(omegaK0)=5.9+1.6-1.3+/-0.5. The charge asymmetries are A_ch(etapi+)=-0.44+/-0.18+/-0.01, A_ch(etaK+)=-0.52+/-0.24+/-0.01, A_ch(omegapi+)=0.03+/-0.16+/-0.01 and A_ch(omegaK+)=-0.09+/-0.17+/-0.01.

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arXiv2003

Rates, Polarizations, and Asymmetries in Charmless Vector-Vector B Meson Decays

With a sample of approximately 89 million BBbar pairs collected with the BABAR detector, we perform a search for B meson decays into pairs of charmless vector mesons (phi, rho, and K*). We measure the branching fractions, determine the degree of longitudinal polarization, and search for CP violation asymmetries in the processes B->phiK*+, B->phiK*0, B->rho0K*+, and B->rho0rho+. We also set an upper limit on the branching fraction for the decay B->rho0rho0.

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arXiv2003

Measurement of Time-Dependent CP Asymmetries and Constraints on sin(2beta+gamma) with Partial Reconstruction of B0 -> D*-+ pi+- Decays

We present a measurement of time-dependent CP-violating asymmetries in decays of neutral B mesons to the final states D*-+ pi+-, using approximately 82 million B B bar events recorded by the BABAR experiment at the PEP-II e+ e- storage ring. Events containing these decays are selected with a partial reconstruction technique, in which only the high-momentum pi+- from the B decay and the low-momentum pi-+ from the D*-+ decay are used. We measure the amplitude of the asymmetry to be -0.063 +- 0.024(stat.) +- 0.014(syst.) and compute bounds on |sin(2beta + gamma)|.

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arXiv2003

J/psi production via initial state radiation in e+ e- --> mu+ mu- gamma at an e+e- center-of-mass energy near 10.6 GeV

We have used a study of the process e+e- --> mu+ mu- gamma at a center-of-mass energy near the Y(4S) resonance for a mu+ mu- invariant mass range near the J/psi mass to extract the cross section sigma(e+e- --> J/psi gamma --> mu+ mu- gamma). The data set, corresponding to an integrated luminosity of 88.4 fb-1, was collected using the BaBar detector at the PEP-II collider. We measure the product Gamma(J/psi --> e+e-)B(J/psi --> mu+ mu-) to be 0.330 +/- 0.008(stat) +/- 0.007(syst) keV. Using the world averages for B(J/psi --> mu+ mu-) and B(J/psi --> e+e-), we derive the J/psi electronic and total widths: Gamma(J/psi --> e+e-)=5.61+/-0.20 keV and Gamma=94.7+/-4.4 keV.

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arXiv2003

Search for the B Meson Decay to eta' phi

We present preliminary results of a search for the decay B0 -> eta' phi. The data were recorded with the BaBar detector at the PEP-II asymmetric-energy B-meson Factory at SLAC and correspond to 89 million B B-bar pairs produced in e+e- annihilation at the Upsilon(4S) resonance. We find no evidence for a signal and set a 90% CL upper limit of BF(B0 -> eta' phi) < 1.0 x 10^-6

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arXiv2003

Measurements of CP-violating Asymmetries and Branching Fractions in B Meson Decays to eta' K

We present measurements of the branching fractions of the decays B+ -> eta' K+ and B0 -> eta' K0. For B0 -> eta' K0s we also measure the time dependent CP-violation parameters S and C, and for B+ ->eta' K+ the time-integrated charge asymmetry Ach. The data sample corresponds to 88.9 million BBbar pairs produced by e+e- annihilation at the Upsillon(4S). The results are B(B+->eta'K+) = (76.9 +/- 3.5 +/- 4.4)*10^-6, B(B0->eta'K0) = (60.6 +/- 5.6 +/- 4.6)*10^-6, S = 0.02+/-0.34 +/- 0.03, C = 0.10+/-0.22 +/- 0.04, and Ach = 0.037 +/- 0.045+/- 0.011.

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arXiv2003

Measurement of |Vcb| using B0 -> D* l nu_l Decays

A preliminary measurement of |Vcb| and the branching fraction BR(B0 -> D* l nu_l) has been performed based on a sample of about 55,700 B0 -> D* l nu_l decays recorded with the BaBar detector. The decays are identified in the D* -> D0 pi final state, with the D0 reconstructed in three different decay modes. The differential decay rate is measured as a function of the relativistic boost of the D* in the B0 rest frame. The value of the differential decay rate at `zero recoil', namely the point at which the D* is at rest in the B0 frame, is predicted in Heavy Quark Effective Theory as a kinematic factor times F(1)|Vcb|, where F(1) is the unique form factor governing the decay. We extrapolate the measured differential decay rate to the zero recoil point and obtain F(1)|Vcb|=(34.03+-0.24+-1.31) x 10^-3. Using a theoretical calculation for F(1) we extract |Vcb| = (37.27+-0.26(stat.)+-1.43(syst.)+1.5-1.2(theo.) x 10^-3. From the integrated decay rate we obtain BR(B0 -> D* l nu_l) = (4.68+-0.03+-0.29)%.

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arXiv2003

Measurement of Branching Fractions and Charge Asymmetries in B Meson Decays to eta(') K*, eta{'} rho, and eta' pi

We present preliminary measurements of branching fractions and charge asymmetries for the B meson decays B -> eta(')K*, B -> eta(')rho, and B+ -> eta' pi+. The data were recorded with the BaBar detector at PEP-II and correspond to 89 x 10^6 B B-bar pairs produced in e+e- annihilation through the Upsilon(4S) resonance. We find the branching fractions B(B0 -> eta K*0) = (19.0 +2.2 -2.1 +/- 1.3) x 10^-6, B(B+ -> eta K*+) = (25.7 +3.8 -3.6 +/- 1.8) x 10^-6, B(B+ -> eta rho+) = (10.5 +3.1 -2.8 +/- 1.3) x 10^-6, B(B+ -> eta' rho+) = (14.0 +5.1 -4.6 +/- 1.9) x 10^-6 (< 22 x 10^-6 with 90% confidence), and B(B+ -> eta' pi+) = (2.8 +1.3 -1.0 +/- 0.3) x 10^-6 (< 4.5 x 10^-6). We also set 90% CL upper limits of B(B0 -> eta' K*0) < 6.4 x 10^-6 and B(B+ -> eta' K*+) < 12 x 10^-6. The time-integrated charge asymmetries are Ach(eta K*0) = +0.03 +/- 0.11 +/- 0.02, Ach(eta K*+) = +0.15 +/- 0.14 +/- 0.02, and Ach(eta rho+) = +0.06 +/- 0.29 +/- 0.02.

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arXiv2003

Measurement of the B --> Xs l+ l- Branching Fraction Using a Sum over Exclusive Modes

We present a measurement of the branching fraction for the flavor-changing neutral current process B --> Xs l+ l- based on a sample of 88.9 \times 10^6 Upsilon(4S) --> BBbar events recorded with the BaBar detector at the PEP-II e+e- storage ring. The final state is reconstructed from pairs of electrons or muons and a hadronic system consisting of one K+/- or K0s and up to two pions, with at most one pi0. Summing over both lepton flavors, we observe a signal of 41 +/- 10(stat) +/- 2(syst) events with a statistical significance of 4.6 sigmas. The inclusive branching fraction is determined to be BF(B --> Xs l+ l-) = [6.3 +/- 1.6(stat) +1.8 -1.5(syst)] 10^{-6} for m(l+ l-) > 0.2 GeV/c^2. All results are preliminary.

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arXiv2003

Measurement of BR(B0 -> Ds*+D*-) and Determination of the Ds+ -> phi pi+ Branching Fraction with a Partial-Reconstruction Method

We present model-independent measurements of the branching fractions ${\cal B}(B^0\to D_s^{*+} D^{*-})$ and ${\cal B}(D_s^+ \to ϕπ^+)$ based on 19.3 $\textup{fb}^{-1}$ of data collected by the $BABAR$ detector at the PEP-II $e^+e^-$ $B$ Factory. Neutral $B$-meson decays to the $D_s^{*+}D^{*-}$ final state are selected with a partial reconstruction of the $D_s^{*+}$; that is, only the $D^{*-}$ and the soft photon from the decay $D_s^{*+} \to \Ds γ$ are reconstructed. The branching fraction ${\cal B}(B^0\to D_s^{*+} D^{*-})$ is extracted from these event yields, while ${\cal B}(D_s^+ \to ϕπ^+)$ is determined by combining this result with a previous measurement of the product ${\cal B}(B^0\to D_s^{*+} D^{*-}) \times {\cal B}(D_s^+ \to ϕπ^+)$ with partial reconstruction of the $D^{*-}$. We obtain the following preliminary results: ${\cal B}(B^0\to D_s^{*+} D^{*-}) = (1.50 \pm 0.16 \pm 0.12)%,$ ${\cal B}(D_s^+ \to ϕπ^+) = (4.7 \pm 0.6 \pm 0.8)%$ where the first error is statistical, and the second systematic.

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arXiv2003

Observation of the Decay $B^{0} \to π^{0}π^{0}$

We present an observation of the decay $B^{0} \to π^{0} π^{0}$ based on a sample of 124 million $B\bar{B}$ pairs recorded by the BABAR detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. We observe $46 \pm 13 \pm 3$ events, where the first error is statistical and the second is systematic, corresponding to a significance of 4.2 standard deviations including systematic uncertainties. We measure the branching fraction $\BR(B^{0} \to π^{0} π^{0}) = (2.1 \pm 0.6 \pm 0.3) \times 10^{-6}$, averaged over $B^{0}$ and $\bar{B}^{0}$ decays.

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arXiv2003

Limits on D0-D0bar Mixing and CP Violation from the Ratio of Lifetimes for Decay to K-pi+, K-K+, and pi-pi+

We present a measurement of $D^0$-$\D0bar$ mixing parameters using the ratios of lifetimes extracted from samples of $D^0$ mesons decaying to $K^-π^+$, $K^-K^+$, and $π^-π^+$. Using 91 ${\rm fb}^{-1}$ of data collected by the BaBar detector at the PEP-II asymmetric-energy $B$ Factory, we obtain a value $Y = (0.8 \pm 0.4 ({\rm stat.}) {}^{+0.5}_{-0.4} ({\rm syst.}))$%, which, in the limit of CP conservation, corresponds to the mixing parameter $y = ΔΓ/2Γ$. Using the difference in lifetimes of $D^0$ and $\D0bar$ mesons, we obtain the CP-violation parameter $ΔY = (-0.8 \pm 0.6 ({\rm stat.}) \pm 0.2 ({\rm syst.}))$%.

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arXiv2003

Evidence for the Rare Decay B -> J/psi eta K

We report evidence for the $B$ meson decays, $B^\pm\to J/ψηK^\pm$ and $B^0\to J/ψηK^0_S$, using {90} million $B\bar B$ events collected at the $\ensuremath{Υ{(4S)}}$ resonance with the \babar detector at the PEP-II $e^+ e^-$ asymmetric-energy storage ring. We obtain preliminary branching fractions in the charged and neutral channels of $(10.8\pm 2.3(stat.)\pm 2.4(syst.))\times 10^{-5}$ and $(8.4\pm 2.6(stat.)\pm 2.7(syst.))\times 10^{-5}$, respectively.

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