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B. Aubert

Publications and source records attributed to B. Aubert.

At least 361 records · Page 20Linked to original sources

Measurement of the time-dependent CP-violating asymmetry in $B^0 \to K^{0}_sπ^0γ$ decays

We present a measurement of the time-dependent CP-violating asymmetry in $B^0 \to K^{*}_0γ$ decays with $K^{*}_0\to K^{0}_sπ^0$ based on 232 million $Υ(4\mathrm{S})\to B\bar{B}$ decays collected with the BaBar detector at the PEP-II asymmetric-energy $e^{+}e^{-}$ collider at SLAC. In a sample containing $157\pm 16$ signal decays, we measure $S_{K^{*}_0γ} = -0.21 \pm 0.40 \pm 0.05$ and $C_{K^{*}_0γ}= -0.40 \pm 0.23 \pm 0.03$, where the first error is statistical and the second systematic. We also explore $B^0 \to K^{0}_sπ^0γ$ decays with $1.1<m_{K^{0}_sπ^0}<1.8$ GeV$/c^2$ and find $59\pm13$ signal events with $S_{K^{0}_sπ^0} = 0.9 \pm 1.0 \pm 0.2$ and $C_{K^{0}_sπ^0} = -1.0 \pm 0.5 \pm 0.2$.

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Observation of B0 Meson decays to a1(1260) pi

We present preliminary measurements of the B meson decay B0 -> a1(1260)+ pi-, with a1(1260)+ --> pi+ pi+ pi-. The data were recorded with the BABAR detector at PEP II and correspond to 218 million BBbar pairs produced in e+e- annihilation through the Upsilon(4S) resonance. We find the branching fractions B(B0 -> a1(1260)+ pi-) = (40.2 +/- 3.9 +/- 3.9) x 10^-6. The fitted values of the a1(1260) parameters are m_a1 = 1.22 +/- 0.02 GeV/c^2 and Gamma_a1= 423 +/- 50 MeV/c^2

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Evidence for B+ -> K0barK+ and B0 -> K0K0bar, and Measurement of the Branching Fraction and Search for Direct CP Violation in B+ -> K0pi+

We present evidence for the b -> d penguin-dominated decays B+ -> K0barK+ and B0 -> K0K0bar with significances of 3.5 and 4.5 standard deviations, respectively. The results are based on a sample of 227 million Y(4S) -> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We measure the branching fractions Br(B+ -> K0barK+) = (1.5 +- 0.5 +- 0.1) x 10^{-6} (< 2.4 x 10^{-6}) and Br(B0 -> K0K0bar) = (1.19^{+0.40}_{-0.35} +- 0.13) x 10^{-6}, where the uncertainties are statistical and systematic, respectively, and the upper limit on the branching fraction for K0barK+ is at the 90% confidence level. We also present improved measurements of the charge-averaged branching fraction Br(B+ -> K0pi+) = (26.0 +- 1.3 +- 1.0) x 10^{-6} and CP-violating charge asymmetry A_CP(K0pi+) = -0.09 +- 0.05 +- 0.01, where the uncertainties are statistical and systematic, respectively.

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Measurement of Time-dependent CP-Violating Asymmetries in B0 -> K+K-K0L Decays

We present preliminary measurements of the CP asymmetry parameters and CP content in B0 --> K+K-K0L decays, with B0 --> phi K0L events excluded. In a sample of 227 M B bar B pairs collected by the BaBar detector at the PEP-II B Factory at SLAC, we find the CP parameters to be S = 0.07 +/- 0.28 (stat) {+0.11} {-0.12} (syst) C = 0.54 +/- 0.22 (stat) {+0.08} {-0.09} (syst) where the first error is statistical and the second is systematic. Estimating the fraction of CP-odd final states from angular moments analysis in the K+K-K0S CP-conjugate final state, f_{odd} (K+K-K0L) = 0.92 +/- 0.07 (stat) +/- 0.06 (syst) we determine sin 2beta_{eff} = 0.09 +/- 0.33, (stat) {+0.13} {-0.14} (syst) +/- 0.10 (syst CP-cont)

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Branching Fraction for B0 -> pi- l+ nu and Determination of |Vub| in Upsilon(4S) -> B0 B0bar Events Tagged by B0bar -> D(*)+ l- nubar

We report preliminary results from a study of the charmless exclusive semileptonic decay B0 -> pi- l+ nu based on the data collected at the Upsilon(4S) resonance using the BABAR detector at SLAC. The analysis uses events in which the signal B meson recoils against a B meson that has been reconstructed in a semileptonic decay B0bar -> D(*)+ l- nubar. We extract the total branching fraction BF(B0 -> pi- l+ nu) = (1.03 +/- 0.25(stat.) +/- 0.13(syst.)) x 10^-4 and the partial branching fractions in three bins of q^2, the invariant mass squared of the lepton-neutrino system. From the partial branching fractions and theoretical predictions for the form factors, we determine the magnitude of the CKM matrix element |Vub|. We find |Vub| = (3.3 +/- 0.4(stat.) +/- 0.2(syst.) +0.8/-0.4(FF)) x 10^-3, where the last error is due to normalization of the form factor.

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Branching Fraction for B+ -> pi0 l+ nu, Measured in Upsilon(4S) -> B Bbar Events Tagged by B- -> D0 l- nubar (X) Decays

We report a preliminary branching fraction of (1.80 +/- 0.37(stat.) +/- 0.23(syst.)) x 10^-4 for the charmless exclusive semileptonic B+ -> pi0 l+ nu decay, where l can be either a muon or an electron. This result is based on data corresponding to an integrated luminosity of 81 fb^-1 collected at the Upsilon(4S) resonance with the BABAR detector. The analysis uses BBbar events that are tagged by a B meson reconstructed in the semileptonic B- -> D0 l- nubar (X) decays, where X can be either a gamma or a pi0 from a D* decay.

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Measurements of the rare decays B -> Kl+l- and B -> K*l+l-

We present measurements of the flavor-changing neutral current decays B -> Kl+l- and B -> K*l+l-, where l+l- is either an e+e- or mu+mu- pair. The data sample comprises 229 X 10^6 Y(4S) -> BBbar decays collected with the BaBar detector at the PEP-II e+e- storage ring. We measure the branching fractions BF(B -> Kl+l-) = (0.34 +- 0.07 +- 0.03) X 10^-6 and BF(B -> K*l+l-) = (0.78^{+0.19}_{-0.17} +/- 0.12) X 10^-6, the direct CP asymmetries of these decays, and the relative abundances of decays to electrons and muons.

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A Study of Production and Decays of Omega_c0 Baryons at BABAR

Production and decay of $Ω_c^0$ baryons is studied with $\sim230 \mathrm{fb}^{-1}$ of data recorded with the BABAR detector at the PEP-II $e^+e^-$ asymmetric-energy storage ring at SLAC. The $Ω_c^0$ is reconstructed through its decays into $Ω^-π^+$, $Ω^-π^+π^+π^-$, and $Ξ^-K^-π^+π^+$ final states. The invariant mass spectra are presented and the signal yields are extracted. Ratios of branching fractions are measured relative to the $Ω^-π^+$ mode \frac{{\cal B}(Ξ^-K^-π^+π^+)}{{\cal B}(Ω^-π^+)} &= 0.31 \pm 0.15\mathrm{(stat.)} \pm 0.04\mathrm{(syst.)}, \frac{{\cal B}(Ω^-π^+π^+π^-)}{{\cal B}(Ω^-π^+)} &< 0.30\qquad (90%\mathrm{CL}). The momentum spectrum (not corrected for efficiency) of $Ω_c^0$ baryons is extracted from decays into $Ω^-π^+$, establishing the first observation of $Ω_c^0$ production from B decays.

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Measurement of the B+ --> p pbar K+ Branching Fraction and Study of the Decay Dynamics

With a sample of 232x10^6 Upsilon(4S) --> BBbar events collected with the BaBar detector, we study the decay B+ --> p pbar K+ excluding charmonium decays to ppbar. We measure a branching fraction Br(B+ --> p pbar K+)=(6.7+/-0.5+/-0.4)x10^{-6}. An enhancement at low ppbar mass is observed and the Dalitz plot asymmetry suggests dominance of the penguin amplitude in this B decay. We search for a pentaquark candidate Theta*++ decaying into pK+ in the mass range 1.43 to 2.00 GeV/c2 and set limits on Br(B+ --> Theta*++pbar)xBr(Theta*++ --> pK+) at the 10^{-7} level.

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A Precision Measurement of the Lambda_c Baryon Mass

The $Λ_c^+$ baryon mass is measured using $Λ_c^+\toΛK^0_S K^+$ and $Λ_c^+\toΣ^0 K^0_S K^+$ decays reconstructed in 232 fb$^{-1}$ of data collected with the BaBar detector at the PEP-II asymmetric-energy $e^+e^-$ storage ring. The $Λ_c^+$ mass is measured to be $2286.46\pm0.14\mathrm{MeV}/c^2$. The dominant systematic uncertainties arise from the amount of material in the tracking volume and from the magnetic field strength.

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Search for B --> Ds(*) Phi

We report on searches for B- --> Ds- Phi and B- --> Ds*- Phi. In the context of the Standard Model, the branching fractions for these decays are expected to be highly suppressed, since they proceed through annhilation of the b and u-bar quarks in the B- meson. Our results are based on 234 million Upsilon(4S) --> B Bbar decays collected with the BaBar detector at SLAC. We find no evidence for these decays, and we set 90% confidence level upper limits on the branching fractions BF(B- --> Ds- Phi) < 1.8x10^(-6) BF(B- --> Ds*- Phi) < 1.1x10^(-5). These results are consistent with Standard Model expectations.

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Measurement of the B+- --> rho+- pi0 Branching Fraction and Direct CP Asymmetry

An improved measurement of the process B+- --> rho+- pi0 is presented. The data sample of 211/fb comprises 232 million Y(4S) --> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC. The yield and CP asymmetry are calculated using an extended maximum likelihood fitting method. The branching fraction and asymmetry are found to be BR(B+- --> rho+- pi0) = [10.0 +- 1.4 (stat) +- 0.9 (syst)]x 10^-6 and Acp(B+- --> rho+- pi0) = -0.01 +- 0.13 (stat) +- 0.02 (syst), superseding previous measurements. The statistical significance of the branching fraction is calculated to be 8.7sigma.

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Search for Lepton-Flavor and Lepton-Number Violation in the Decay tau->lhh

A search for lepton-flavor and lepton-number violation in the decay of the tau lepton into one charged lepton and two charged hadrons is performed using 221.4 $\mathrm{fb}^{-1}$ 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 14 decay modes considered, the observed data are compatible with background expectations, and upper limits are set in the range ${\cal B}(τ\to\ell hh')<(0.7-4.8)\times 10^{-7}$ at 90% confidence level.

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Study of the tau- --> 3h-2h+nu Decay

The branching fraction of the tau- --> 3h- 2h+ nu decay (h= pi, kaon) is measured with the BaBar detector to be (8.56 +/- 0.05 +/- 0.42)E-04 where the first error is statistical and the second systematic. The observed structure of this decay is significantly different from the phase space prediction, with the rho resonance playing a strong role. The decay tau- --> f1 pi nu with the f1 meson decaying to four charged pions, is observed and the branching fraction is measured to be (3.9 +/- 0.7 +/- 0.5)E-04.

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Evidence for the Decay B+- --> K*+- pi0

We have measured the process B+- --> (K*+- --> K+- pi0) pi0 based on 232 million Y(4S) --> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC. From a signal yield of 89 +- 26 events we obtain the branching fraction BR(B+- --> K*+- pi0)=[6.9 +- 2.0 (stat) +- 1.3 (syst)] x10^-6 with a statistical significance of 3.6 standard deviations including systematic uncertainties, and a charge asymmetry of 0.04 +- 0.29 (stat) +- 0.05 (syst).

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Improved Measurement of the CKM Angle alpha Using B0->rho+rho- Decays

We present results from an analysis of B0 -> rho+rho- using 232 million Upsilon(4S) decays collected with the BABAR detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. We measure the longitudinal polarization fraction f_L = 0.978 +- 0.014 (stat) +0.021 -0.029 (syst) and the CP-violating parameters SLong = -0.33 +- 0.24 (stat) +0.08 -0.14 (syst) and CLong = -0.03 +- 0.18 (stat) +- 0.09 (syst). Using an isospin analysis of B -> rho rho decays we determine the unitarity triangle alpha. The solution compatible with the Standard Model is alpha = (100 +- 13) degrees.

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

A search for the nonconservation of lepton flavor number in the decay tau -> mu gamma has been performed using 2.07 x 10^8 e+e- -> tau+ tau- events produced at a center-of-mass energy near 10.58 GeV with the BABAR detector at the PEP-II storage ring. We find no evidence for a signal and set an upper limit on the branching ratio of BR(tau -> mu gamma) < 6.8 x 10^-8 at 90% confidence level.

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