arXiv subjects

B. Aubert

Publications and source records attributed to B. Aubert.

At least 37 records · Page 2Linked to original sources

arXiv2009

Precise measurement of the e+ e- to pi+ pi- (gamma) cross section with the Initial State Radiation method at BABAR

A precise measurement of the cross section of the process e+ e- to pi+ pi- (gamma) from threshold to an energy of 3 GeV is obtained with the initial state radiation (ISR) method using 232 fb^-1 of data collected with the BABAR detector at e+ e- center-of-mass energies near 10.6 GeV. The ISR luminosity is determined from a study of the leptonic process e+ e- to mu+ mu- gamma (gamma). The leading-order hadronic contribution to the muon magnetic anomaly calculated using the pi pi cross section measured from threshold to 1.8 GeV is (514.1 +-2.2(stat} +-3.1(syst}) x 10^{-10}.

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arXiv2009

Search for b-> u transitions in B0 -> D0 K*0 decays

We present a study of the decays B0 -> D0 K*0 and B0 -> barD0 K*0 with K*0 -> K+pi-. The D0 and the barD0 mesons are reconstructed in the final states f=K+pi-, K+pi-pi0, K+pi-pi+pi- and their charge conjugates. Using a sample of 465 million BBbar pairs collected with the Babar detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we measure the ratio R_{ADS}=[Gamma(barB0 -> [f]_D barK*0)+Gamma(B0 -> [bar{f}]_D K*0)]/ [Gamma(barB0 -> [bar{f}]_D barK*0)+Gamma(B0 -> [f]_D K*0)] for the three final states. We do not find significant evidence for a signal and set the following limits at 95% probability: R_{ADS}(Kpi)<0.244, R_{ADS}(Kpipi0)<0.181 and R_{ADS}(Kpipipi)<0.391. From the combination of these three results, we find that the ratio rS between the b -> u and the b -> c amplitudes lies in the range [0.07,0.41] at 95% probability.

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arXiv2009

A Search for Invisible Decays of the Upsilon(1S)

We search for invisible decays of the Upsilon(1S) meson using a sample of 91.4 x 10^{6} Upsilon(3S) mesons collected at the BaBar/PEP-II B-factory. We select events containing the decay Upsilon(3S) -> pi+ pi- Upsilon(1S) and search for evidence of an undetectable Upsilon(1S) decay recoiling against the dipion system. We set an upper limit on the branching fraction BR(Upsilon(1S) -> invisible) < 3.0 x 10^{-4} at the 90% confidence level.

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arXiv2009

Measurement of Semileptonic B Decays into Orbitally Excited Charmed Mesons

We present a study of B decays into semileptonic final states containing charged and neutral $D_1(2420)$ and $D_2^*(2460)$. The analysis is based on a data sample of $208 fb^{-1}$ collected at the $Υ(4S)$ resonance with the BaBar detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. With a simultaneous fit to four different decay chains, the semileptonic branching fractions are extracted from measurements of the mass difference $Δm=m(D**)-m(D)$ distributions. Product branching fractions are determined to be $BR(B^+ -> D_1^0 \ell^+ ν_{\ell}) x BR(D_1^0 -> D*^+ π^-) = (2.97 +/- 0.17 +/- 0.17) x 10^{-3}$, $BR(B^+ -> D_2^{*0} \ell^+ ν_{\ell}) x BR(D_2^{*0} -> D^{(*)+} π^-) = (2.29 +/- 0.23 +/- 0.21) x 10^{-3}$, $BR(B^0 -> D_1^- \ell^+ ν_{\ell}) x BR(D_1^- -> D*^0 π^-) = (2.78 +/- 0.24 +/- 0.25) 10^{-3}$ and $BR(B^0 -> D_2^{*-} \ell^+ ν_{\ell}) x BR(D_2^{*-} -> D^{(*)0} π^-) = (1.77 +/- 0.26 +-/ 0.11) 10^{-3}$. In addition we measure the branching ratio $Γ(D_2^* -> D π^-)/Γ(D_2^* -> D^{(*)} π^-) = 0.62 +/- 0.03 +/- 0.02$.

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arXiv2009

Search for a Narrow Resonance in e+e- to Four Lepton Final States

Motivated by recent models proposing a hidden sector with $\sim$GeV scale force carriers, we present a search for a narrow dilepton resonance in 4 lepton final states using $536fb^{-1}$ collected by the BaBar detector. We search for the reaction, $e^+e^-\to W^\prime W^\prime\to(l^+l^-)(l^{\prime+}l^{\prime-})$, where the leptons carry the full 4-momentum and the two dilepton pair invariant masses are equal. We do not observe a significant signal and we set 90% upper limits of $σ(e^+e^-\to W^\prime W^\prime\to(e^+e^-)(e^+e^-))<(15-70) ab$, $σ(e^+e^-\to W^\prime W^\prime\to(e^+e^-)(μ^+μ^-))<(15-40) ab$, and $σ(e^+e^-\to W^\prime W^\prime\to(μ^+μ^-)(μ^+μ^-))<(11-17) ab$ in the $W^\prime$ mass range between 0.24 and 5.3GeV. Under the assumption that the $W^\prime$ coupling to electrons and muons is the same, we obtain a combined upper limit of $σ(e^+e^-\to W^\prime W^\prime\to(l^+l^-)(l^{\prime+}l^{\prime-}))<(25-60) ab$. Using these limits, we constrain the product of the SM-dark sector mixing and the dark coupling constant in the case of a non-Abelian Higgsed dark sector.

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arXiv2009

Observation and study of baryonic B decays: B -> D() p pbar, D() p pbar pi, and D(*) p pbar pi pi

We present a study of ten B-meson decays to a D(*), a proton-antiproton pair, and a system of up to two pions using BaBar's data set of 455x10^6 BBbar pairs. Four of the modes (B0bar -> D0 p anti-p, B0bar -> D*0 p anti-p, B0bar -> D+ p anti-p pi-, B0bar -> D*+ p anti-p pi-) are studied with improved statistics compared to previous measurements; six of the modes (B- -> D0 p anti-p pi-, B- -> D*0 p anti-p pi-, B0bar -> D0 p anti-p pi- pi+, B0bar -> D*0 p anti-p pi- pi+, B- -> D+ p anti-p pi- pi-, B- -> D*+ p anti-p pi- pi-) are first observations. The branching fractions for 3- and 5-body decays are suppressed compared to 4-body decays. Kinematic distributions for 3-body decays show non-overlapping threshold enhancements in m(p anti-p) and m(D(*)0 p) in the Dalitz plots. For 4-body decays, m(p pi-) mass projections show a narrow peak with mass and full width of (1497.4 +- 3.0 +- 0.9) MeV/c2, and (47 +- 12 +- 4) MeV/c2, respectively, where the first (second) errors are statistical (systematic). For 5-body decays, mass projections are similar to phase space expectations. All results are preliminary.

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arXiv2009

Measurement of D0-D0bar Mixing using the Ratio of Lifetimes for the Decays D0->K-pi+ and K+K-

We measure the rate of D0-D0bar mixing with the observable yCP=(tauKpi/tauKK)-1, where tauKK and tauKpi are respectively the mean lifetimes of CP-even D0->K+K- and CP-mixed D0->K-pi+ decays, using a data sample of 384/fb collected by the Babar detector at the SLAC PEP-II asymmetric-energy B Factory. From a sample of D0 and D0bar decays where the inital flavor of the decaying meson is not determined, we obtain yCP = [1.12 +/- 0.26 (stat) +/- 0.22 (sys)]%, which excludes the no-mixing hypothesis at 3.3 sigma, including both statistical and systematic uncertainties. This result is in good agreement with a previous Babar measurement of yCP obtained from a sample of D*+->D0pi+ events, where the D0 decays to K-pi+, K+K-, and pi+pi-, which is disjoint with the untagged D0 events used here. Combining the two results taking into account statistical and systematic uncertainties, where the systematic uncertainties are assumed to be 100% correlated, we find yCP = [1.16 +/- 0.22 (stat) +/- 0.18 (sys)]%, which excludes the no-mixing hypothesis at 4.1 sigma.

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arXiv2009

Measurement and interpretation of moments in inclusive semileptonic decays Bbar --> X_c l- nubar

We present results for the moments of observed spectra in inclusive semileptonic B-meson decays to charm hadrons Bbar --> X_c l- nubar. Moments of the hadronic-mass and the combined mass-and-energy spectra for different minimum electron or muon momenta between 0.8 and 1.9 GeV/c are obtained from a sample of 232x10^{6} Y(4S) --> B Bbar events, collected with the BABAR detector at the PEP-II asymmetric-energy B-meson factory at SLAC. We also present a re-evaluation of the moments of electron-energy spectra and partial decay fractions BR(Bbar --> X_c e- nubar for minimum electron momenta between 0.6 and 1.5 GeV/c based on a sample of 51x10^{6} Y(4S) --> B Bbar events. The measurements are used for the extraction of the total decay fraction, the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |V_cb|, the quark masses m_b and m_c, and four heavy-quark QCD parameters in the framework of a Heavy Quark Expansion (HQE). We find BR(Bbar --> X_c l- nubar) = (10.64 +/- 0.17 +/- 0.06)% and |V_cb| = (42.05 +/- 0.45 +/- 0.70) x 10^{-3}.

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arXiv2009

Search for B-meson decays to b1rho and b1K*

We present a search for decays of $B$ mesons to final states with a $b\_1$ meson and a $ρ$ or $K^*(892)$ meson. The search is based on a data sample consisting of 465 million $B\kern 0.18em{\kern -0.18em B}{}$ pairs collected by the {\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}} detector at the SLAC National Accelerator Laboratory. We do not observe any statistically significant signal. The upper limits we set on the branching fractions range from 1.4 to $8.0 \times 10^{-6}$ at the 90% confidence level (C.L.), including systematic uncertainties.

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arXiv2009

Dalitz Plot Analysis of D_s+ -> pi+ pi- pi+

A Dalitz plot analysis of approximately 13,000 Ds+ decays to pi+pi-pi+ has been performed. The analysis uses a 384 fb-1 data sample recorded by the BaBar detector at the PEP-II asymmetric-energy e+e- storage ring running at center of mass energies near 10.6 GeV. Amplitudes and phases of the intermediate resonances which contribute to this final state are measured. A high precision measurement of the ratio of branching fractions is performed: BR(Ds+ -> pi+pi-pi+)/BR(Ds+ -> K+ K- pi+)=0.199 +/- 0.004 +/- 0.009. Using a model-independent partial wave analysis, the amplitude and phase of the S-wave have been measured.

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arXiv2009

Measurement of the Branching Fraction and Lambda-bar Polarization in B0 -> Lambda-bar p pi-

We present a measurement of the B0 --> Lambda-bar p pi- branching fraction performed using the BaBar detector at the PEP-II asymmetric e+e- collider. Based on a sample of 467 million BB-bar pairs we measure B(B0 --> Lambda-bar p pi-) = [3.07 pm 0.31 (stat.) pm 0.23 (syst.)] x 10^{-6}. The measured differential spectrum as a function of the dibaryon invariant mass m(Lambda p) shows a near-threshold enhancement similar to that observed in other baryonic B decays. We study the Lambda-bar polarization as a function of Lambda-bar energy in the B0 rest frame (E*_Lambda) and compare it with theoretical expectations of fully longitudinally right-polarized Lambda-bar at large E*_Lambda.

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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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