arXiv subjects

The BABAR Collaboration

Publications and source records attributed to The BABAR Collaboration.

At least 163 records · Page 9Linked to original sources

arXiv2009

Observation and Polarization Measurement of B0 --> a1(1260)+ a1(1260)- Decay

We present measurements of the branching fraction B and the longitudinal polarization fraction fL for B0 -> a1(1260)+ a1(1260)- decays, with a1(1260)+/- -> π- π+ π+/-. The data sample, collected with the detector BaBar at the SLAC National Accelerator Laboratory, represents 465 10^6 produced BBbar pairs. We measure B(B0 -> a1(1260)+ a1(1260)-) x [B(a1(1260)+ -> π- π+ π+)]^2 = (11.8 \pm 2.6 \pm 1.6) 10^{-6} and fL = 0.31 \pm 0.22 \pm 0.10, where the first uncertainty is statistical and the second systematic. The decay mode is measured with a significance of 5.0 standard deviations including systematic uncertainties.

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arXiv2009

Improved limits on lepton flavor violating tau decays to l phi, l rho, l K* and l K*bar

We search for the neutrinoless, lepton-flavor-violating tau decays tau -> l V^0, where l is an electron or muon and V^0 is a vector meson reconstructed as phi -> K^+K^-, rho -> pi^+pi^-, K^* -> K^+pi^-, or K^*bar -> K^-pi^+. The analysis has been performed using 451 fb^{-1} of data collected at an e^+e^- center-of-mass energy near 10.58 GeV with the BaBar detector at the PEP-II storage rings. The number of events found in the data is compatible with the background expectation, and upper limits on the branching fractions are set in the range (2.6-19) x 10^{-8} at the 90% confidence level.

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arXiv2009

Search for B^0 Meson Decays to π^0 K^0_SK^0_S, ηK^0_S K^0_S, and η^{\prime}K^0_SK^0_S

We describe searches for $B^0$ meson decays to the charmless final states $π^0 K^0_SK^0_S$, $ηK^0_S K^0_S$, and $η^{\prime}K^0_SK^0_S$. The data sample corresponds to $467 \times 10^{6}$ $B\bar{B}$ pairs produced in $e^+e^-$ annihilation and collected with the BABAR detector at the SLAC National Accelerator Laboratory. We find no significant signals and determine the 90% confidence level upper limits on the branching fractions, in units of $10^{-7}$, $\cal{B}(B^0 \ra π^0K^0_SK^0_S) <9 $, $\cal{B}(B^0 \ra ηK^0_SK^0_S) <10$, and $\cal{B}(B^0 \ra η^{\prime}K^0_SK^0_S) <20$.

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arXiv2009

Dalitz Plot Analysis of B- -> D+ pi- pi-

We report on a Dalitz plot analysis of B- -> D+ pi- pi- decays, based on a sample of about 383 million Upsilon(4S) -> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC. We find the total branching fraction of the three-body decay: BR(B- -> D+ pi- pi-) = (1.08 +/- 0.03 +/- 0.05) x 10^-3. The masses and widths of D^{*0}_2 and D^{*0}_0, the 2+ and 0+ cubar P-wave states decaying to D+ pi-, are measured: mass_{D^{*0}_2} = (2460.4 +/- 1.2 +/- 1.2 +/- 1.9) MeV/c2, width_{D^{*0}_2} = (41.8 +/- 2.5 +/- 2.1 +/- 2.0) MeV, mass_{D^{*0}_0} = (2297 +/- 8 +/- 5 +/- 19) MeV/c2 and width_{D^{*0}_0} = (273 +/- 12 +/- 17 +/-45) MeV. The stated errors reflect the statistical and systematic uncertainties, and the uncertainty related to the assumed composition of signal events and the theoretical model.

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arXiv2009

Measurement of Branching Fractions and CP and Isospin Asymmetries in B -> K*(892) gamma Decays

We present an analysis of the decays B0 -> K*0 gamma and B+ -> K*+ gamma using a sample of 383 million BBbar events collected with the BaBar detector at the PEP2 asymmetric energy B factory. We measure the branching fractions BF[B0 -> K*0 Gamma] = 4.47 +/- 0.10 +/- 0.16 x 10^-5 and BF[B+ -> K*+ Gamma] = 4.22 +/- 0.14 +/- 0.16 x 10^-5. We constrain the direct CP asymmetry to be -0.033 < Acp < 0.028 and the isopin asymmetry to be 0.017 < \Delta0- < 0.116, where the limits are determined at the 90% confidence interval and include both statistical systematic uncertainties.

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arXiv2009

Search for the Rare Leptonic Decays \boldmath{\Blnu} ($\ell=e,μ$)

We have performed a search for the rare leptonic decays \Bp \to \ellp \nul ($l=e,μ$), using data collected at the \FourS resonance by the \babar\ detector at the \pep2 storage ring. In a sample of 468 million \BB pairs we find no evidence for a signal and set an upper limit on the branching fractions $\BR(\bmunu) < 1.0\times10^{-6}$ and $\BR(\benu) < 1.9\times10^{-6}$ at the 90% confidence level, using a Bayesian approach.

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arXiv2009

Measurement of the gamma gamma* --> pi0 transition form factor

We study the reaction e+e- --> e+e-pi0 and measure the gamma gamma* --> pi0 transition form factor in the momentum transfer range from 4 to 40 GeV^2. The analysis is based on 442 fb^-1 of integrated luminosity collected at PEP-II with the BABAR detector at e+e- center-of-mass energies near 10.6 GeV.

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arXiv2009

Search for Dimuon Decays of a Light Scalar Boson in Radiative Transitions Upsilon -> gamma A0

We search for evidence of a light scalar boson in the radiative decays of the Upsilon(2S) and Upsilon(3S) resonances: Upsilon(2S,3S)-> gamma A0, A0 -> mu^+ mu^-. Such a particle appears in extensions of the Standard Model, where a light CP-odd Higgs boson naturally couples strongly to b-quarks. We find no evidence for such processes in the mass range 0.212<= m(A0)<= 9.3 GeV in the samples of 99*10^6 Upsilon(2S) and 122*10^6 Upsilon(3S) decays collected by the BABAR detector at the PEP-II B-factory and set stringent upper limits on the effective coupling of the b quark to the A0. We also limit the dimuon branching fraction of the eta_b meson: BR(eta_b->mu^+mu^-)<0.9% at 90% confidence level.

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arXiv2009

Time-dependent amplitude analysis of B0 --> K0S pi+ pi-

We perform a time-dependent amplitude analysis of $B^0 \to K^0_Sπ^+π^-$ decays to extract the CP violation parameters of $f_0(980) K^0_S$ and $ρ^0(770) K^0_S$ and the direct CP asymmetry of $K^{*+}(892) π^-$. The results are obtained from a data sample of $(383 \pm 3) \times 10^6$ $B\bar{B}$ decays, collected with the BABAR detector at the PEP-II asymmetric-energy $B$ factory at SLAC. We find two solutions, with an equivalent goodness-of-fit. Including systematic and Dalitz plot model uncertainties, the combined confidence interval for values of the CP parameter $β_{eff}$ in $B^0$ decays to $f_0(980) K^0_S$ is $18^o < β_{eff} < 76^o$ at 95% confidence level (C.L). CP conservation in $B^0$ decays to $f_0(980) K^0_S$ is excluded at $3.5σ$ including systematic uncertainties. For $B^0$ decays to $ρ^0(770) K^0_S$, the combined confidence interval is $-9^o < β_{eff} < 57^o$ at 95% C.L. In decays to $K^{*+}(892) π^-$ we measure the direct CP asymmetry to be $A_{CP}=-0.20 \pm 0.10 \pm 0.01 \pm 0.02$. The measured phase difference (including $B^0\bar{B}^0$ mixing) between decay amplitudes of $B^0 \to K^{*+}(892) π^-$ and $\bar{B}^0 \to K^{*-}(892) π^+$, excludes the interval $-137^o < ΔΦ(K^{*+}(892) π^-) < -5^o$ at 95% C.L.

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arXiv2009

Measurement of the B+ -> omega l+ nu and B+ -> eta l+ nu Branching Fractions

We present a study of the charmless semileptonic B-meson decays B+ -> omega l+ nu and B+ -> eta l+ nu. The analysis is based on 383 million BBbar pairs recorded at the Upsilon(4S) resonance with the BABAR detector. The omega mesons are reconstructed in the channel omega -> pi+ pi- pi0 and the eta mesons in the channels eta -> pi+ pi- pi0 and eta -> gamma gamma. We measure the branching fractions B(B+ -> omega l+ nu) = (1.14 +- 0.16 (stat) +- 0.08 (syst)) x 10^-4 and B(B+ -> eta l+ nu) = (0.31 +- 0.06 (stat) +- 0.08 (syst)) x 10^-4.

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arXiv2009

Measurement of CP-Violating Asymmetries in the B0->K+K-Ks Dalitz Plot

We present a preliminary measurement of CP-violation parameters in the decay B0->K+K-Ks, using approximately 465 million BBbar events collected by the BABAR detector at SLAC. Reconstructing the neutral kaon as Ks->pi+pi- or Ks->pi0pi0, we analyze the Dalitz plot distribution and measure fractions to intermediate states. We extract CP parameters from the asymmetries in amplitudes and phases between B0 and B0bar decays across the Dalitz plot. From a fit to the whole Dalitz plot, we measure beta_eff = 0.44 +/- 0.07 +/- 0.02, A_CP = 0.03 +/- 0.07 +/- 0.02, where the first uncertainties are statistical and the second ones are systematic. For decays to phiKs, we measure beta_eff = 0.13 +/- 0.13 +/- 0.02, A_CP = 0.14 +/- 0.19 +/- 0.02. For decays to f0Ks, we measure beta_eff = 0.15 +/- 0.13 +/- 0.03, A_CP = 0.01 +/- 0.26 +/- 0.07. From a fit to the region of the Dalitz plot with m_{K+K-}>1.1 GeV/c^2, we measure beta_eff = 0.52 +/- 0.08 +/- 0.03, A_CP = 0.05 +/- 0.09 +/- 0.04.

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arXiv2009

Measurement of Time-Dependent CP Asymmetry in B0->ccbar K(*)0 Decays

We present updated measurements of time-dependent CP asymmetries in fully reconstructed neutral B decays containing a charmonium meson. The measurements reported here use a data sample of (465+/-5) million Upsilon(4S)->BBbar decays collected with the Babar detector at the PEPII asymmetric energy e+e- storage rings operating at the SLAC National Accelerator Laboratory. The time-dependent CP asymmetry parameters measured from JpsiKs, JpsiKL, Psi(2S)Ks, Chi_c1Ks, eta_cKs and JpsiK*0 decays are: C_f = 0.024+/-0.020(stat)+/-0.016(syst) and -η_f S_f = 0.687+/-0.028(stat)+/-0.012(syst).

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arXiv2009

Measurement of |V_cb| and the Form-Factor Slope in Bbar -> D l- nubar Decays in Events Tagged by a Fully Reconstructed B Meson

We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V_cb| and the form-factor slope rho^2 in Bbar -> Dl- nubar decays based on 460 million BBar events recorded at the Upsilon(4S) resonance with the BaBar detector. BBar -> Dl- nubar decays are selected in events in which a hadronic decay of the second B meson is fully reconstructed. We measure the differential decay rate and determine G(1) |V_cb|= (43.0 \pm 1.9 \pm 1.4)\times 10^{-3} and rho^2 = 1.20 \pm 0.09 \pm 0.04, where G(1) is the the hadronic form factor at the point of zero recoil. We also determine the exclusive branching fractions and find BF(B^- -> D0l- nubar) = (2.31 \pm 0.08 \pm 0.09)% and BF (B0bar -> D+ l^- nubar)=(2.23 \pm 0.11 \pm 0.11)%.

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arXiv2009

Dalitz Plot Analysis of B+- --> pi+-pi+-pi-+ Decays

We present a Dalitz plot analysis of charmless B+- decays to the final state pi+-pi+-pi-+ using a sample of (465+-5)x10^-6 BBbar pairs collected by the BABAR experiment at \sqrt{s} = 10.58 GeV. We measure the branching fractions BF(B+- --> pi+-pi+-pi-+) = (15.2+-0.6+-1.2+-0.4)x10^-6, BF(B+- --> rho0(770)pi+-) = (8.1+-0.7+-1.2^{+0.4}_{-1.1})x10^-6, BF(B+- --> f2(1270)pi+-) = (1.57+-0.42+-0.16^{+0.53}_{-0.19})x10^-6, and BF(B+- --> pi+-pi+-pi-+ nonresonant) = (5.3+-0.7+-0.6^{+1.1}_{-0.5})x10^-6, where the uncertainties are statistical, systematic, and model-dependent, respectively. Measurements of branching fractions for the modes B+- --> rho0(1450)pi+- and B+- --> f0(1370)pi+- are also presented. We observe no significant direct CP asymmetries for the above modes, and there is no evidence for the decays B+- --> chiC0 pi+-, or B+- --> chiC2 pi+-.

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arXiv2009

Search for Second-Class Currents in tau- -> omega.pi-.nu_tau

We report an analysis of tau- decaying into omega.pi-.nu_tau with omega -> pi+pi-pi0 using a data sample containing nearly 320 million tau pairs collected with the BABAR detector at the PEP-II B-Factory. We find no evidence for second-class currents and we set an upper limit of 0.69% at 90% confidence level for the fraction of second-class currents in this decay mode.

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arXiv2009

Constraints on the CKM angle gamma in B^0 --> barD^0 (D^0) K^*0 from a Dalitz analysis of D^0 --> K_S pi^+ pi^-

We present constraints on the angle gamma of the Unitarity Triangle with a Dalitz analysis of neutral D decays to K_Spi^+pi^- from the processes B^0 -> barD^0 K^*0 (barB^0 -> D^0 barK^*0) and B0 -> D0 K*0 (barB^0 -> barD^0 barK^*0) with K^*0 -> K^+pi^- (barK^*0 -> K^-pi^+). Using a sample of 371 10^6 BBbar pairs collected with the Babar detector at PEP-II, we measure the angle gamma as a function of r_S, the magnitude of the average ratio between b -> u and b -> c amplitudes. Combining this result with the available information on r_S, we obtain gamma = (162 +- 56) degrees or (342 +- 56) degrees and r_S<0.55 at 95% probability.

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arXiv2009

Evidence for X(3872) --> psi(2S) gamma in B+/- --> X(3872) K+/- decays, and a study of B --> ccbar gamma K

In a search for B --> ccbar gamma K decays with the BaBar detector, where ccbar includes J/psi and psi(2S), and K includes K+, Ks, and K*(892), we find evidence for X(3872) --> J/psi gamma and X(3872) --> psi(2S) gamma with 3.6 sigma and 3.5 sigma significance, respectively. We measure the product of branching fractions BR(B+ --> X(3872) K+) x BR(X(3872) --> J/psi gamma) = (2.8 +/- 0.8(stat.) +/- 0.2(syst.)) x 10^(-6) and BR(B+ --> X(3872) K+) x BR(X(3872) --> psi(2S) gamma) = (9.9 +/- 2.9(stat.) +/- 0.6(syst.)) x 10^(-6).

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arXiv2009

Exclusive Initial-State-Radiation Production of the $D \bar D$, $D \bar D^$, and $D^ \bar D^*$, Systems

We perform a study of the exclusive production of $D \bar D$, $D \bar D^*$, and $D^* \bar D^*$ in initial-state-radiation events, from $e^+ e^-$ annihilations at a center-of-mass energy near 10.58 GeV, to search for charmonium and possible new resonances. The data sample corresponds to an integrated luminosity of 384 $fb^{-1}$ and was recorded by the BaBar experiment at the PEP-II storage rings. The $D \bar D$, $D \bar D^*$, and $D^* \bar D^*$ mass spectra show clear evidence of several $ψ$ resonances. However, there is no evidence for $Y(4260) \to D \bar D^*$ or $Y(4260)\to D^* \bar D^*$.

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