arXiv subjects

BABAR Collaboration

Publications and source records attributed to BABAR Collaboration.

At least 37 records · Page 2Linked to original sources

arXiv2006

Determination of |Vub| from Measurements of the Electron and Neutrino Momenta in Inclusive Semileptonic B Decays

We present a determination of the CKM matrix element |Vub| based on the analysis of semileptonic B decays from a sample of 88 million Upsilon(4S) decays collected with the BABAR detector at the PEP-II e+e- storage ring. Charmless semileptonic B decays are selected using measurements of the electron energy and the invariant mass squared of the electron-neutrino pair. We obtain |Vub| = (3.95 +/- 0.26 ^{+0.58}_{-0.42} +/- 0.25) x 10^{-3}, where the errors represent experimental uncertainties, heavy quark parameter uncertainties, and theoretical uncertainties, respectively.

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arXiv2006

Study of the X(3872) and Y(4260) in B0-->J/psi pi+ pi- K0 and B-->J/psi pi+ pi- K- decays

We present results of a search for the X(3872) in B0-->X(3872)KS0,X(3872)-->J/psi pi+ pi-, improved measurements of B-->X(3872)K-, and a study of the J/psi pi+ pi- mass region above the X(3872). We use 232x106 B[overline B] pairs collected at the Upsilon(4S) resonance with the BABAR detector at the PEP-II e+e- asymmetric-energy storage rings. The results include the 90% confidence interval 1.34x10-6 X(3872)K0,X-->J/psi pi+ pi-)<10.3x10-6 and the branching fraction BR(B-->X(3872)K-,X-->J/psi pi+ pi-)=(10.1+-2.5+-1.0)x10-6. We observe a (2.7+-1.3+-0.2)MeV/c2 mass difference of the X(3872) produced in the two decay modes. Furthermore, we search for the Y(4260) in B decays and set the 95% C.L. upper limit BR(B-->Y(4260)K-,Y(4260)-->J/psi pi+ pi-)<2.9x10-5.

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arXiv2006

Search for Lepton Flavor Violation in the Decay tau -> electron gamma

A search for the non-conservation of lepton flavor in the decay tau -> electron gamma has been performed with 2.07 x 10^8 e+e- -> tau+ tau- events collected by the BABAR detector at the PEP-II storage ring at a center-of-mass energy near 10.58 GeV. We find no evidence for a signal and set an upper limit on the branching ratio of BR(tau -> electron gamma) < 1.1 x 10^-7 at 90% confidence level.

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arXiv2005

Measurement of the Inclusive Electron Spectrum in Charmless Semileptonic B Decays Near the Kinematic Endpoint and Determination of |Vub|

We present a measurement of the inclusive electron spectrum in charmless semileptonic B decays near the kinematic limit for B->X_c eνtransitions, using a sample of 88 million Upsilon(4S) decays recorded by the BABAR detector. Partial branching fraction measurements are performed in five overlapping intervals of the electron momentum. For the interval of 2.0-2.6 GeV/c we obtain ΔBr(B->X_u eν) = (0.572+-0.041(stat)+-0.065(syst))x10^{-3}. Combining this result with shape function parameters extracted from BABAR measurements of moments of the inclusive photon spectrum in B->X_s+gamma decays and moments of the hadron mass and lepton energy spectra in B->X_c lνdecays we determine |V_{ub}|=((4.44+-0.25(exp) ^{+0.42}_{-0.38}(SF)+-0.22(theory))x10^{-3}. Here the first error represents the combined statistical and systematic experimental uncertainties of the partial branching fraction measurement, the second error refers to the uncertainty of the determination of the shape function parameters, and the third error is due to theoretical uncertainties in the QCD calculations.

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arXiv2005

Measurement of CP Observables for the Decays B+/- --> D0_CP K*+/-

Using a sample of 232 million Upsilon(4S) --> B Bbar events collected with the BABAR detector at the PEP-II B Factory in 1999-2004, we study B- --> D0 K*(892)- decays where K*- --> KS pi- and D0 --> K-pi+, K-pi+pi0, K-pi+pi+pi- (non-CP final states); K+K-, pi+pi- (CP+ eigenstates); KSpi0, KSphi and KSomega (CP- eigenstates). We measure four observables that are sensitive to the angle gamma of the CKM unitarity triangle; the partial-rate charge asymmetries A_CP+/- and the ratios of the B-decay branching fraction in CP+/- and non-CP decays R_CP+/-: A_CP+ = -0.08 +/- 0.19 (stat.) +/- 0.08 (syst.) A_CP- = -0.26 +/- 0.40 (stat.) +/- 0.12 (syst.) R_CP+ = 1.96 +/- 0.40 (stat.) +/- 0.11 (syst.) R_CP- = 0.65 +/- 0.26 (stat.) +/- 0.08 (syst.)

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arXiv2005

Search for the rare decay B0bar --> D*0 gamma

We report on a search for the rare decay B0bar --> D*0 gamma, which in the standard model is dominated by W-exchange. The analysis is based on a data sample comprising 87.8 x 10^6 BBbar pairs collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. No significant signal is observed, and an upper limit on the branching fraction of 2.5 x 10^{-5} at the 90% confidence level is obtained.

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arXiv2005

Measurement of the Partial Branching Fraction for Inclusive Charmless Semileptonic B Decays and Extraction of $|V_{ub}|$

Charmless semileptonic decays, ${\bar{B}} \to X_u \ell \barν$, are studied in a sample of 232 million $B\bar{B}$ decays recorded with the BaBar detector, in events where the decay of the second $B$ meson is fully reconstructed. Inclusive charmless decays are selected in kinematic regions where the dominant background from semileptonic B decays to charm is reduced by requirements on the hadronic mass $M_X$ and the momentum transfer $q^2$. The partial branching fraction for ${\bar{B}} \to X_u \ell \barν$ decays for $M_X<1.7$ GeV/c^2 and $q^2>8$ Gev^2/c^4 is measured to be $Δ{\cal{B}}({\bar{B}} \to X_u \ell \barν) = (0.87 \pm 0.09_{\rm stat}\pm 0.09_{\rm sys}\pm 0.01_{\rm th})\times 10^{-3}$. The CKM matrix element $|V_{ub}|$ is determined by using theoretical calculations of phase space acceptances. Theoretical uncertainties in this extrapolation are reduced by using the inclusive $b \to s γ$ photon spectrum and moments of the $b \to c \ell \barν$ lepton energy and hadronic invariant mass.

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arXiv2005

Production and decay of Xic0 at BABAR

Using 116.1 fb^-1 of data collected by the BABAR detector, we present an analysis of Xic0 production in B decays and from the ccbar continuum, with the Xic0 decaying into Omega- K+ and Xi- pi+ final states. We measure the ratio of branching fractions B(Xic0 -> Omega- K+)/B(Xic0 -> Xi- pi+) to be 0.294 +- 0.018 +- 0.016, where the first uncertainty is statistical and the second is systematic. The Xic0 momentum spectrum is measured on and 40 MeV below the Upsilon(4S) resonance. From these spectra the branching fraction product B(B -> Xic0 X) x B(Xic0 -> Xi- pi+) is measured to be (2.11 +- 0.19 +- 0.25) x 10^-4 and the cross-section product sigma(e+ e- -> Xic0 X) x B(Xic0 -> Xi- pi+) from the continuum is measured to be (388 +- 39 +- 41) fb at a center-of-mass energy of 10.58 GeV.

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arXiv2005

Dalitz Plot Analysis of D0-->K0bar K+ K-

A Dalitz plot analysis of approximately 12500 D0 events reconstructed in the hadronic decay D0-->K0bar K+ K- is presented. This analysis is based on a data sample of 91.5 fb-1 collected with the BaBar detector at the PEP-II asymmetric-energy e+ e- storage rings at SLAC running at center-of-mass energies on and 40 MeV below the Y4S resonance. The events are selected from e+ e- --> c cbar annihilations using the decay D*+ --> D0 pi+. The following ratio of branching fractions has been obtained: BR = Gamma(D0-->K0bar K+ K-)/Gamma(D0-->K0bar pi+ pi-) = (15.8+/-0.1(stat.)+/-0.5(syst.)x 10-2 Estimates of fractions and phases for resonant and non-resonant contributions to the Dalitz plot are also presented. The a0(980)-->K Kbar projection has been extracted with little background. A search for CP asymmetries on the Dalitz plot has been performed.

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arXiv2005

Measurement of the Cabibbo-Kobayashi-Maskawa angle gamma in B-+ -> D(*)K-+ decays with a Dalitz analysis of D -> K0s pi- pi+

We report on a measurement of the Cabibbo-Kobayashi-Maskawa CP-violating phase gamma through a Dalitz analysis of neutral D decays to K0s pi- pi+ in the processes B-+ -> D(*)K-+, D* -> D pi0, D gamma. Using a sample of 227 million BBbar pairs collected by the BaBar detector, we measure the amplitude ratios rB = 0.12+/-0.08+/-0.03+/-0.04 and rB* = 0.17+/-0.10+/-0.03+/-0.03, the relative strong phases deltaB = 104+/-45+17-21+16-24, and deltaB*= -64+/-41+14-12+/-15 between the amplitudes A(B- -> Dbar(*)0 K-) and A(B- -> D(*)0 K-), and gamma = 70+/-31+12-10+14-11. The first error is statistical, the second is the experimental systematic uncertainty and the third reflects the Dalitz model uncertainty. The results for the strong and weak phases have a two-fold ambiguity.

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arXiv2005

Amplitude Analysis of the Decay B+- -> pi+- pi+- pi-+

We present a Dalitz-plot analysis of charmless B+- decays to the final state pi+- pi+- pi-+ using 210 fb^-1 of data recorded by the BABAR experiment at sqrt(s) = 10.58 GeV. We measure the branching fractions B(B+- -> pi+- pi+- pi-+) = (16.2 +- 1.2 +- 0.9) x 10^-6 and B(B+- -> rho^0(770) pi+-) = (8.8 +- 1.0 +- 0.6 +0.1-0.7) x 10^-6. Measurements of branching fractions for the quasi-two-body decays B+- -> rho^0(1450) pi+-, B+- -> f_0(980) pi+- and B+- -> f_2(1270) pi+- are also presented. We observe no charge asymmetries for the above modes, and there is no evidence for the decays B+- -> chic0 pi+-, B+- -> f_0(1370) pi+- and B+- -> sigma pi+-.

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arXiv2005

Measurement of CP Asymmetries in B0-> KS pi0 pi0 Decays

We present a preliminary measurement of the time-dependent CP asymmetry for the neutral B-meson decay into the CP = +1 final state KS pi0 pi0, with KS-> pi+ pi- and pi0-> gamma gamma. We use a sample of approximately 227 million B-meson pairs recorded at the Y(4S) resonance by the BaBar detector at the PEP-II B-Factory at SLAC. From a maximum likelihood fit we extract the mixing-induced CP-violation parameter S = 0.84 +/- 0.71(stat} +/- 0.08{syst) and the direct CP-violation parameter C = 0.27 +/- 0.52(stat) +/- 0.13(syst}, where the first uncertainty is statistical and the second systematic.

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arXiv2005

A Study of b --> c and b -->u Interference in the Decay B- --> [K+ pi-]_D K*-

Using a sample of 232 x 10^6 Upsilon(4S)--> B B-bar events collected with the BABAR detector at the PEP-II B-factory we study the decay B- --> [K+ pi-]_D K*- where the K+ pi- is either from a Cabibbo-favored D0-bar decay or doubly-suppressed D0 decay. We measure two observables that are sensitive to the CKM angle gamma; the ratio R of the charge-averaged branching fractions for the suppressed and favored decays; and the charge asymmetry A of the suppressed decays: R=0.046 +/- 0.031(stat.) +/- 0.008(syst.) A=-0.22 +/- 0.61(stat.) +/- 0.17(syst.).

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arXiv2005

Measurement of gamma in B-+ -> D() K-+ and B-+ -> D K-+ decays with a Dalitz analysis of D -> Ks pi- pi+

We present a measurement of the Cabibbo-Kobayashi-Maskawa CP-violating phase gamma with a Dalitz plot analysis of neutral D-meson decays to the Ks pi- pi+ final state from B-+ -> D(*) K-+ and B-+ -> D K*-+ decays, using a sample of 227 million BBbar pairs collected by the BaBar detector. We measure gamma = 67 +/- 28 +/- 13 +/- 11, where the first error is statistical, the second is the experimental systematic uncertainty and the third reflects the Dalitz model uncertainty. This result suffers from a two-fold ambiguity. The contribution to the Dalitz model uncertainty due to the description of the pipi S-wave in D0 -> Ks pi- pi+, evaluated using a K-matrix formalism, is found to be 3 degrees.

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arXiv2005

Dalitz Plot Study of B0 --> K+K-K0S Decays

We present a study of the dynamics in B0 --> K+ K- K0S decays with approximately 230 million BBbar events collected by the BABAR detector at SLAC. We find that the Dalitz plot distribution is best parameterized with the phi K0S mode, an S-wave K+ K- resonance near 1500 MeV/c^2, and a large non-resonant contribution. We set limits on resonances not included in our model, and study models for the non-resonant contribution.

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arXiv2005

Measurement of Time-Dependent CP-Violating Asymmetries in B0 Meson Decays to eta'K0L

We present a preliminary measurement of CP-violating parameters S and C from fits of the time-dependence of B0 meson decays to eta'K0L. The data were recorded with the BABAR detector at PEP-II and correspond to 232 10^6 BBbar pairs produced in e+e- annihilation through the Y(4S) resonance. By fitting the time-dependent CP asymmetry of the reconstructed B0 --> eta'K0L events, we find S = 0.60 +- 0.31 +- 0.04 and C = 0.10 +- 0.21 +- 0.03, where the first error quoted is statistical and the second is systematic. We also perform a combined fit using both eta'K0S and eta'K0L data, and find S = 0.36 +- 0.13 +- 0.03 and C = -0.16 +- 0.09 +- 0.02.

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arXiv2005

Measurements of the Branching Fraction and Time-Dependent CP-Asymmetries of B0->J/Psi pi0 Decays

We present measurements of the branching fraction and time-dependent CP asymmetries in B0->J/Psi pi0 decays based on (231.8 +/- 2.6)*10^6 Upsilon(4S) -> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy B factory at SLAC during the years 1999-2004. We obtain a branching fraction B(B0->J/Psi pi0) = (1.94 +/- 0.22 (stat) +/- 0.17 (syst))*10^-5. We also measure the CP asymmetry parameters C = -0.21 +/- 0.26 (stat) +/- 0.09 (syst) and S = -0.68 +/- 0.30 (stat) +/- 0.04 (syst). All results presented in this paper are preliminary.

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arXiv2005

Measurement of CP-voilating parameters in fully reconstructed B->D(*)+-pi-+ and B->D+-rho-+ decays

We present a preliminary measurement of the CP-violating parameters in fully reconstructed B->D^(*)+-pi-+ and B->D^+-rho-+ decays in approximately 232 million Y(4S)->BBbar$ decays collected with the BaBar detector at the PEP-II asymmetric-energy B factory at SLAC. From a maximum likelihood fit to the time-dependent decay distributions we obtain for the parameters related to the CP violation quantity sin(2beta+gamma): a[Dpi] = -0.013 +/- 0.022 (stat.) +/- 0.007 (syst.), clep[Dpi] = -0.043 +/- 0.042 (stat.) +/- 0.011 (syst.), a[D*pi] = -0.043 +/- 0.023 (stat.) +/- 0.010 (syst.), clep[D*pi] = 0.047 +/- 0.042 (stat.) +/- 0.015 (syst.), a[Drho] = -0.024 +/- 0.031 (stat.) +/- 0.010 (syst.), clep[Drho] = -0.098 +/- 0.055 (stat.) +/- 0.019 (syst.).

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