arXiv subjects

B. Aubert

Publications and source records attributed to B. Aubert.

At least 199 records · Page 11Linked to original sources

arXiv2007

Search for $D^0-{\bar D}^0$ Mixing Using Doubly Flavor Tagged Semileptonic Decay Modes

We have searched for $D^0 - \bar{D}^0$ mixing in $D^{*+} \to π^+ D^0$ decays with $D^0 \to K^{(*)} e ν$ in a sample of $e^+ e^- \to {c\bar c}$ events produced near 10.58 GeV. The charge of the slow pion from charged $D^*$ decay tags the charm flavor at production, and it is required to be consistent with the flavor of a fully reconstructed second charm decay in the same event. We observe 3 mixed candidates compared to 2.85 background events expected from simulation. We ascribe a 50% systematic uncertainty to this expected background rate. We find a central value for the mixing rate of $0.4 \times 10^{-4}$. Using a frequentist method, we set corresponding 68% and 90% confidence intervals at $(-5.6, 7.4) \times 10^{-4}$ and $(-13, 12) \times 10^{-4}$, respectively.

hep-ex↗

arXiv2007

Improved Measurements of the Branching Fractions for B0 --> pi+pi- and B0 --> K+pi-, and a Search fro B0 --> K+K-

We present measurements of the branching fractions for the charmless two-body decays $\Bz\to\pip\pim$ and $\Bz\to\Kp\pim$, and a search for the decay $\Bz\to\Kp\Km$. We include the effects of final-state radiation from the daughter mesons for the first time, and quote branching fractions for the inclusive processes $\Bz\to h^+ h^{\prime -} nγ$, where $h$ and $h^\prime$ are pions or kaons. The maximum value of the sum of the energies of the $n$ undetected photons, $E_γ^{\rm max}$, is mode-dependent. Using a data sample of approximately 227 million \upsbb decays collected with the \babar\ detector at the \pep2 asymmetric-energy \epem collider at SLAC, we measure: \begin{eqnarray*} {\cal B} (\Bz \to \pip\pim nγ;\: E_γ^{\rm max}=150\mev) & = & (5.1\pm 0.4\pm 0.2)\times 10^{-6}, {\cal B} (\Bz \to \Kp\pim nγ;\: E_γ^{\rm max}=105\mev) & = & (18.1\pm 0.6\pm 0.6)\times 10^{-6}, {\cal B} (\Bz \to \Kp\Km nγ;\: E_γ^{\rm max}=59\mev) & < & 0.5 \times 10^{-6} (90% {\rm confidence level}), \end{eqnarray*} where the first uncertainty is statistical and the second is systematic. Theoretical calculations can be used to extrapolate from the above measurements the non-radiative branching fractions, ${\cal B}^0$. Using one such calculation, we find: \begin{eqnarray*} {\cal B}^0 (\Bz \to \pip\pim) & = & (5.5\pm 0.4\pm 0.3)\times 10^{-6}, {\cal B}^0 (\Bz \to \Kp\pim) & = & (19.1\pm 0.6\pm 0.6)\times 10^{-6}, {\cal B}^0 (\Bz \to \Kp\Km) & < & 0.5 \times 10^{-6} (90% {\rm confidence level}). \end{eqnarray*} Meaningful comparison between theory and experiment, as well as combination of measurements from different experiments, can be performed only in terms of these non-radiative quantities.

hep-ex↗

arXiv2007

Search for B0->phiK+pi- Decays with Large K+pi- Invariant Mass

Motivated by the polarization anomaly in the B->phi(1020)K*(892) decay, we extend our search for other K* final states in the decay B0->phi(1020)K^*0 with the K*0->K+pi- invariant mass above 1.6 GeV. The final states considered include the K*(1680)0, K3*(1780)0, K4*(2045)0, and a Kpi spin-zero nonresonant component. We also search for B0->phiDbar0 decay with the same final state. The analysis is based on a sample of about 384 million BBbar pairs recorded with the BABAR detector. We place upper limits on the branching fractions BR(B0->phiK*(1680)0)<3.5*10^-6, BR(B0->phiK3*(1780)0)<2.7*10^-6, BR(B0->phiK4*(2045)0)<15.3*10^-6, and BR(B0->phiDbar0)<11.7*10^-6 at 90% C.L. The nonresonant contribution is consistent with the measurements in the lower invariant mass range.

hep-ex↗

arXiv2007

Evidence for the Rare Decay B+ --> Ds+ pi0

We have searched for the rare decay B+ --> Ds+ pi0. The analysis is based on a sample of 232 million Upsilon(4S) --> B anti-B decays collected with the BABAR detector at the PEP-II e+ e- storage ring. We find 19.6 signal events, corresponding to a significance of 4.7 sigma. The extracted signal yield including statistical and systematic uncertainties is 20.1+6.8+0.4 -6.0-1.5, and we measure B(B+ --> Ds+ pi0) =(1.5 +0.5 -0.4 +- 0.1 +- 0.2) 10^-5, where the first uncertainty is statistical, the second is systematic, and the last is due to the uncertainty on the Ds+ decay and its daughter decay branching fractions.

hep-ex↗

arXiv2007

Branching Fraction Measurements of B+ -> rho+ gamma, B0 -> rho0 gamma, and B0 -> omega gamma

We present a study of the decays B+ -> rho+ gamma, B0 -> rho0 gamma, and B0 -> omega gamma. The analysis is based on data containing 347 million BBbar events recorded with the BaBar detector at the PEP-II asymmetric B factory. We measure the branching fractions BR(B+ -> rho+ gamma) = (1.10 +0.37/-0.33 +/- 0.09) x 10-6 and BR(B0 -> rho0 gamma) = (0.79 +0.22/-0.20 +/- 0.06) x 10-6, and set a 90% C.L. upper limit BR(B0 -> omega gamma) < 0.78 x 10-6. We also measure the isospin-averaged branching fraction BR(B->rho/omega gamma) = (1.25 +0.25/-0.24 +/- 0.09) x 10-6, from which we determine |Vtd/Vts| = 0.200 +0.021/-0.020 +/- 0.015, where the first uncertainty is experimental and the second is theoretical.

hep-ex↗

arXiv2007

Search for the radiative leptonic decay B+ --> gamma l+ nu

We present the results of a search for $B^{+}\toγ\ell^{+}ν_{\ell}$, where $\ell = e, μ$. We use a sample of 232 million $B\bar{B}$ pairs recorded at the $Υ(4S)$ with the BaBar detector at the PEP-II $B$ Factory. We measure a partial branching fraction $Δ\mathcal{B}$ in a restricted region of phase space that reduces the effect of theoretical uncertainties, requiring the lepton energy to be between 1.875 and 2.850GeV, the photon energy to be between 0.45 and 2.35GeV, and the cosine of the angle between the lepton and photon momenta to be less than -0.36, with all quantities computed in the $Υ(4S)$ center-of-mass frame. We find $Δ\mathcal{B}(B^{+}\toγ\ell^{+}ν_{\ell}) = (-0.3^{+1.3}_{-1.5} ({stat}) \pm 0.6 ({syst}) \pm 0.1 ({th})) \times 10^{-6}$, assuming lepton universality. Interpreted as a 90% C.L. Bayesian upper limit, the result corresponds to $1.7\times10^{-6}$ for a prior flat in amplitude, and $2.3\times10^{-6}$ for a prior flat in branching fraction.

hep-ex↗

arXiv2007

Branching fraction and charge asymmetry measurements in B to J/psi pi pi decays

We study the decays B0 to J/psi pi+pi- and B+ to J/psi pi+pi0, including intermediate resonances, using a sample of 382 million BBbar pairs recorded by the BaBar detector at the PEP-II e+e- B factory. We measure the branching fractions B(B0 ->J/psi rho0) = (2.7 +/- 0.3 +/- 0.17) x 10-5 and B(B+ ->J/psi rho+) = (5.0 +/- 0.7 +/-0.31) x 10-5. We also set the following upper limits at the 90% confidence level: B(B0 -> J/psi pi+ π- non-resonant) < 1.2 x 10-5, B(B0 -> J/psi f_2(1270)) < 4.6 x 10-6, and B(B+ -> J/psi pi+ pi0 non-resonant) < 4.4 x 10-6. We measure the charge asymmetry in charged B decays to J/psi rho to be -0.11 +/- 0.12 +/- 0.08.

hep-ex↗

arXiv2007

Measurement of the Hadronic Form Factor in D0 --> K- e+ nue Decays

The shape of the hadronic form factor f+(q2) in the decay D0 --> K- e+ nue has been measured in a model independent analysis and compared with theoretical calculations. We use 75 fb(-1) of data recorded by the BABAR detector at the PEPII electron-positron collider. The corresponding decay branching fraction, relative to the decay D0 --> K- pi+, has also been measured to be RD = BR(D0 --> K- e+ nue)/BR(D0 --> K- pi+) = 0.927 +/- 0.007 +/- 0.012. From these results, and using the present world average value for BR(D0 --> K- pi+), the normalization of the form factor at q2=0 is determined to be f+(0)=0.727 +/- 0.007 +/- 0.005 +/- 0.007 where the uncertainties are statistical, systematic, and from external inputs, respectively.

hep-ex↗

arXiv2007

Search for Neutral B-Meson Decays to a0pi, a0K, etarho0, and etaf0

We present a search for B0 decays to charmless final states involving an eta meson, a charged pion and a second charged pion or kaon. The data sample corresponds to 383x10^6 BBbar pairs collected with the BABAR detector operating at the PEP-II asymmetric-energy B Factory at SLAC. We find no significant signals and determine the following 90% C.L. upper limits: BR(B->a0-pi+) x BR(a0- -> etapi-) < 3.1x10^-6, BR(B->a0-K+) x BR(a0- -> etapi-) < 1.9x10^-6, BR(B->a0(1450)-pi+) x BR(a0(1450)- -> etapi-) < 2.3x10^-6, BR(B->a0(1450)-K+) x BR(a0(1450)- -> etapi-) < 3.1x10^-6, BR(B->etarho0) < 1.5x10^-6, and BR(B->eta f0(980)) x BR(f0(980)- -> pi+pi-) < 0.4x10^-6.

hep-ex↗

arXiv2007

Measurement of ${CP}\xspace$ Violation Parameters with a Dalitz Plot Analysis of $B^\pm \to D_{π^+π^-π^0} K^\pm$

We report the results of a CP violation analysis of the decay B+/- --> D(pipipi0)K+/-, where D(pipipi0) indicates a neutral D meson detected in the final state pi+pi-pi0, excluding K_S pi0. The analysis makes use of 324 million e+e- --> BB events recorded by the BaBar experiment at the PEP-II e+e- storage ring. By analyzing the pi+pi-pi0 Dalitz plot distribution and the B+/- --> D(pipipi0)K+/- branching fraction and decay rate asymmetry, we calculate parameters related to the phase gamma of the CKM unitarity triangle. We also measure the magnitudes and phases of the components of the D0 --> pi+pi-pi0 decay amplitude.

hep-ex↗

arXiv2007

Measurements of $Λ^+_c$ Branching Fractions of Cabibbo-Suppressed Decay Modes involving $Λ$ and $Σ^{0}$

We measure the branching ratios of the Cabibbo-suppressed decays $Λ^+_c$ $\to$ $Λ$ $K^+$ and $Λ^+_c$ $\to$ $Σ^{0}$ $K^+$ %(measured with improved accuracy). relative to the Cabibbo-favored decay modes $Λ^+_c$ $\to$ $Λ$ $π^+$ and $Λ^+_c$ $\to$ $Σ^{0}$ $π^+$ to be $ 0.044 \pm 0.004 (\textnormal{stat.}) \pm 0.003 \ (\textnormal{syst.})$ and $ 0.039 \pm 0.005 (\textnormal{stat.}) \pm 0.003 (\textnormal{syst.})$, respectively. We set an upper limit on the branching ratio at 90 % confidence level for $Λ^+_c$ $\to$ $Λ$ $K^+ π^+ π^-$ to be $ 4.1 \times 10^{-2}$ relative to $Λ^+_c$ $\to$ $Λ$ $π^+$ and for $Λ^+_c$ $\to$ $Σ^{0}$ $K^+ π^+ π^-$ to be $ 2.0 \times 10^{-2}$ relative to $Λ^+_c$ $\to$ $Σ^{0}$ $π^+$. We also measure the branching fraction for the Cabibbo-favored mode $Λ^+_c$ $\to$ $Σ^{0}$ $π^+$ relative to $Λ^+_c$ $\to$ $Λ$ $π^+$ to be $0.977 \pm 0.015 (\textnormal{stat.}) \pm 0.051 (\textnormal{syst.})$. This analysis was performed using a data sample with an integrated luminosity of 125 fb$^{-1}$ collected by the $BABAR$ detector at the PEP-II asymmetric-energy $B$ factory at SLAC.

hep-ex↗

arXiv2007

Measurement of CP-Violating Asymmetries in B0-->(rhopi)0 Using a Time-Dependent Dalitz Plot Analysis

We report a measurement of CP-violating asymmetries in B0-->(rhopi)0-->pi+pi-pi0 decays using a time-dependent Dalitz plot analysis. The results are obtained from a data sample of 375 million Y(4S) --> BBbar decays, collected by the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC. We measure 26 coefficients of the bilinear form-factor terms occurring in the time-dependent decay rate of the B0 meson. We derive the physically relevant quantities from these coefficients. In particular, we measure a constraint on the angle alpha of the Unitarity Triangle.

hep-ex↗

arXiv2007

Measurement of the Relative Branching Fractions of Bbar --> D/D*/D** l^- anti-nu_l Decays in Events with a Fully Reconstructed B Meson

We determine the relative branching fractions of semileptonic B decays to charmed final states. The measurement is performed on the recoil from a fully reconstructed B meson in a sample of 362 million BBbar pairs collected at the Upsilon(4S) resonance with the BaBar detector. A simultaneous fit to a set of discriminating variables is performed on a sample of Bbar --> D X l^- anti-nu_l decays to determine the contributions from the different channels. We measure Gamma(B- --> D l^- anti-nu_l)/Gamma (B- --> D X l^- anti-nu_l)= 0.227 +/- 0.014 +/- 0.016, Gamma(B- --> D* l^- anti-nu_l)/Gamma (B- --> D X l^- anti-nu_l)= 0.582 +/- 0.018 +/- 0.030 and Gamma(B- --> D** l^- anti-nu_l)/Gamma (B- --> D X l^- anti-nu_l)= 0.191 +/- 0.013 +/- 0.019 for the charged B sample, and Gamma(B0bar --> D l^- anti-nu_l)/Gamma (B0bar --> D X l^- anti-nu_l)= 0.215 +/- 0.016 +/- 0.013, Gamma(B0bar --> D* l^- anti-nu_l)/Gamma (B0bar --> D X l^- anti-nu_l)= 0.537 +/- 0.031 +/- 0.036 and Gamma(B0bar --> D** l^- anti-nu_l)/Gamma (B0bar --> D X l^- anti-nu_l)= 0.248 +/- 0.032 +/- 0.030 for the neutral B sample, where uncertainties are statistical and systematic, respectively.

hep-ex↗

arXiv2007

Observation of CP violation in B^0 -> eta' K^0 Decays

We present measurements of the time-dependent CP-violation parameters S and C in B^0 --> eta' K^0 decays. The data sample corresponds to 384 million B Bar pairs produced by e^+ e^- annihilation at the Y(4S). The results are S = 0.58 +- 0.10 +- 0.03 and C = -0.16 +- 0.07 +- 0.03. We observe mixing-induced CP violation with a significance of 5.5 standard deviations in this b -> s penguin dominated mode.

hep-ex↗

arXiv2007

Evidence for D0-anti-D0 Mixing

We present evidence for D0-anti-D0 mixing in D0 --> K+pi- decays from 384 fb^{-1} of e+e- colliding-beam data recorded near sqrt(s) 10.6 GeV with the BaBar detector at the PEP-II storage rings at SLAC. We find the mixing parameters x'^2 = [-0.22 +- 0.30 (stat.) +- 0.21 (syst.)] x 10^{-3} and y' = [9.7 +- 4.4 (stat.) +- 3.1 (syst.)] x 10^{-3}, and a correlation between them of -0.94. This result is inconsistent with the no-mixing hypothesis with a significance of 3.9 standard deviations. We measure R_D, the ratio of doubly Cabibbo-suppressed to Cabibbo-favored decay rates, to be [0.303 +- 0.016 (stat.) +- 0.010 (syst.)]%. We find no evidence for \CP violation.

hep-ex↗

arXiv2007

Vector-Tensor and Vector-Vector Decay Amplitude Analysis of B0->phi K*0

We perform an amplitude analysis of the decays B0->phi K^*_2(1430)0, phi K^*(892)0, and phi(K pi)^0_S-wave with a sample of about 384 million BBbar pairs recorded with the BABAR detector. The fractions of longitudinal polarization f_L of the vector-tensor and vector-vector decay modes are measured to be 0.853 +0.061-0.069 +-0.036 and 0.506 +-0.040 +-0.015, respectively. Overall, twelve parameters are measured for the vector-vector decay and seven parameters for the vector-tensor decay, including the branching fractions and parameters sensitive to CP-violation.

hep-ex↗

arXiv2007

Evidence for B0->rho0rho0 Decay and Implications for the CKM Angle alpha

We search for the decays B0->rho0rho0, B0->rho0f0, and B0->f0f0 in a sample of about 384 million Upsilon(4S)->BBbar decays collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We find evidence for B0->rho0rho0 with 3.5 sigma significance and measure the branching fraction BR = (1.07+-0.33+-0.19)10^-6 and longitudinal polarization fraction f_L = 0.87+-0.13+-0.04, where the first uncertainty is statistical, and the second is systematic. The uncertainty on the CKM unitarity angle alpha due to penguin contributions in B-> rho rho decays is 18 degrees at the 1 sigma level. We also set upper limits on the B0->rho0f0 and B0->f0f0 decay rates.

hep-ex↗

arXiv2007

Search for Lepton Flavor Violating Decays $τ^\pm \to \ell^\pm{π^0}, \ell^\pmη, \ell^\pm{η^\prime}$

A search for lepton flavor violating decays of the $τ$ lepton to a lighter mass lepton and a pseudoscalar meson has been performed using 339 fb$^{-1}$ of $e^+e^-$ annihilation data collected at a center-of-mass energy near 10.58 GeV by the BaBar detector at the SLAC PEP-II storage ring. No evidence of signal has been found, and upper limits on the branching fractions are set at $10^{-7}$ level.

hep-ex↗