arXiv subjects

B. Aubert

Publications and source records attributed to B. Aubert.

At least 541 records · Page 30Linked to original sources

arXiv2003

A Search for the Decay $B^{-}\to K^{-} ν\barν$

We present a search for the rare flavour-changing neutral-current decay $B^{-}\to K^{-} ν\barν$ based on a sample of $(86.9 \pm 1.0) \times 10^{6}$ $Υ(4S) \to $B\bar{B}$ events collected by the BABAR experiment at the SLAC B-factory. Signal candidate events are selected by fully reconstructing a $B^+ \to \bar{D}^{0} X^+$ decay, where $X^+$ represents a combination of up to three charged pions or kaons and up to two $π^0$ candidates. The charged tracks and calorimeter clusters not used in the $B^+$ reconstruction are required to be compatible with a $B^{-}\to K^{-} ν\barν$ decay. We observe a total of three signal candidate events with an expected background of $2.7 \pm 0.8$, resulting in a preliminary limit of $\mathcal{B}(B^{-}\to K^{-} ν\barν) < 1.05 \times 10^{-4}$ at the 90% confidence level. This search is combined with the results of a previous and statistically independent preliminary BABAR search for $B^{-}\to K^{-} ν\barν$ to give a limit of $\mathcal{B}(B^{-}\to K^{-} ν\barν) < 7.0 \times 10^{-5}$ at the 90% confidence level.

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arXiv2003

A Search for B- -> tau- nu-bar Recoiling Against a Fully Reconstructed B

We present a search for the B- ->tau- nu-bar decay in a data sample of 82 fb^(-1) collected at the Y(4S) resonance with the BaBar detector at the SLAC PEP-II asymmetric B Factory. Continuum and combinatorial backgrounds are suppressed by selecting a sample of events with one completely reconstructed B. The decay products of the other B in the event are analyzed to search for a B- -> tau- nu-bar decay. The tau lepton is identified in the following decay channels: tau->e, tau->mu, tau->pi, tau->pi pi0 nu, tau->pi pi pi nu. We find no evidence for a signal and set a 90% C.L. upper limit of BR(B->tau nu) < 7.7x10^(-4). We combine this result with another BaBar measurement searching for B- -> tau- nu-bar decays in a sample with one B meson reconstructed in semi-leptonic channels. The two samples are statistically independent. We obtain a combined 90% C.L. upper limit of BR(B->tau nu) < 4.1x10^(-4). All results are preliminary.

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arXiv2003

Observation of a Narrow Meson Decaying to Ds+pi0 at a Mass of 2.32 GeV/c^2

We have observed a narrow state near 2.32 GeV/c^2 in the inclusive Ds+ pi0 invariant mass distributionfrom e+e- annihilation data at energies near 10.6 GeV. The observed width is consistent with the experimental resolution. The small intrinsic width and the quantum numbers of the final state indicate that the decay violates isospin conservation. The state has natural spin-parity and the low mass suggests a JP=0+ assignment. The data sample corresponds to an integrated luminosity of 91 fb-1 recorded by the BABAR detector at the PEP2 asymmetric-energy e+e- storage ring.

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arXiv2003

Rare B Decays into States Containing a J/psi Meson and a Meson with ssbar Quark Content

We report a study of the B meson decays, B+ -> J/psi phi K+, B0 -> J/psi phi K0S, B0 -> J/psi phi, B0 -> J/psi eta and B0 -> J/psi eta' using 56 million BBbar events collected at the Y(4S) resonance with the BABAR detector at the PEP-II e+ e- asymmetric-energy storage ring. We measure the branching fractions B(B+ -> J/psi phi K+) = (4.4 +- 1.4(stat) +- 0.5(syst)) * 10-5 and B(B0 -> J/psi phi K0S) = (5.1 +- 1.9(stat) +- 0.5(syst)) * 10^-5, and set upper limits at 90% confidence level for the branching fractions B(B0 -> J/psi phi) < 9.2 * 10^-6, B(B0 -> J/psi eta)< 2.7 * 10^-5, and B(B0 -> J/psi eta')< 6.3 * 10-5.

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arXiv2003

Search for D0D0bar Mixing and a Measurement of the Doubly Cabibbo-suppressed Decay Rate in D0 -> K pi Decays

We present results of a search for $D^0$-$\kern 0.2em\bar{\kern -0.2em D}{}^0$~mixing and a measurement of $R_{\rm D}$, the ratio of doubly Cabibbo-suppressed decays to Cabibbo-favored decays, based on an analysis of $D^0 \to K^{+}π^{-}$ decays in 57.1~${fb}^{-1}$ of data collected at or just below the $Υ{(4S)}$ resonance with the {\slshape BABAR} detector at the PEP-II collider. Our results are compatible with no mixing and no $CP$ violation. At the 95% C.L., allowing for CP violation, we find the mixing parameters ${x^{\prime}}^2<0.0022$ and $-0.056<y^{\prime}<0.039$, and the mixing rate $R_{\rm M} < 0.16%$. In the limit of no mixing, $R_{\rm D} = (0.357 \pm 0.022 \hbox{(stat.)} \pm 0.027 \hbox{(syst.)})%$ and the $CP$~violating asymmetry \mbox{$A_{\rm D} = 0.095 \pm 0.061 \hbox{(stat.)} \pm 0.083 \hbox{(syst.)}$.}

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arXiv2003

Limits on the Lifetime Difference of Neutral B Mesons and on CP, T, and CPT Violation in B0-B0bar Mixing

Using events in which one of two neutral B mesons from the decay of an Y(4S) resonance is fully reconstructed, we set limits on the lifetime difference between the two neutral-B mass eigenstates and on CP, T, and CPT violation in B0-B0bar mixing. Both CP and non-CP eigenstates were obtained from the 88 million Y(4S)->B0B0bar decays collected between 1999 and 2002 with the BABAR detector at the PEP-II asymmetric-energy B-Factory at SLAC. We determine six independent parameters governing mixing (dm, dGamma/Gamma), CPT/CP violation (Re(z), Im(z)), and CP/T violation (Imλ(CP), |q/p|), where λ(CP) characterizes B0 and B0bar decays to states of charmonium plus K_S or K_L. The preliminary results are: sgn(Reλ(CP))*dGamma/Gamma = -0.008+-0.037(stat)+-0.018(syst) [-0.084,0.068], |q/p| = 1.029+-0.013(stat)+-0.011(syst) [1.001,1.057], (Reλ(CP)/|λ(CP)|)*Rez = 0.014+-0.035(stat)+-0.034(syst) [-0.072,0.101], Imz = 0.038+-0.029(stat)+-0.025(syst) [-0.028,0.104] . The values inside square brackets indicate the 90% confidence-level intervals. For Imλ(CP)/|λ(CP)| and dm we find values consistent with recent results from other analyses. These results are consistent with Standard Model expectations.

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arXiv2003

Measurements of the branching fractions of exclusive charmless B meson decays with $η^prime$ or $ω$ mesons

We present the results of searches for B decays to charmless two-body final states containing $η^\prime$ or $ω$ mesons, based on 20.7 fb$^{-1}$ of data collected with the BABAR detector. We find the branching fractions ${\cal B}(B^+\toη^\prime K^+) = (70\pm 8\pm 5)\times 10^{-6}$, ${\cal B}(B^0\toη^\prime K^0) = (42^{+13}_{-11}\pm 4)\times 10^{-6}$, and ${\cal B}(B^+\toωπ^+)=6.6^{+2.1}_{-1.8}\pm 0.7)\times 10^{-6}$ where the first error quoted is statistical and the second systematic. We give measurements of four additional modes for which the 90% confidence level upper limits are ${\cal B}(B^0\toωK^0) < 13\times 10^{-6}$, ${\cal B}(B^+\toη^\prime π^+) < 12\times 10^{-6}$, ${\cal B}(B^+\to ωK^+) < 4\times 10^{-6}$, and ${\cal B}(B^0\toωπ^0) < 3\times 10^{-6}$.

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arXiv2003

Observation of B Meson Decays to eta pi and eta K

We present preliminary measurements of the B meson decays B+->etapi+, B+->etaK+, and B0->etaK0. The data were recorded with the BABAR detector at PEP II and correspond to 88.9 million BBbar pairs produced in e+e- annihilation through the Upsilon(4S) resonance. We find the branching fractions B(B+->etapi+) = (4.2 +1.0-0.9 +/- 0.3)x 10^-6 and B(B+->etaK+) = (2.8 +0.8-0.7 +/-0.2)x10^-6. We set a 90% CL upper limit of B(B0->etaK0) < 4.6x10^-6. The time-integrated charge asymmetries are Ach(B+->etapi+) = -0.51 +0.20-0.18 +/-0.01 and Ach(B+->etaK+) = -0.32 +0.22-0.18 +/-0.01.

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arXiv2003

Observation of B Meson Decays to omegapi+, omegaK+, and omegaK0

We present preliminary measurements of B meson decays to omegapi+, omegaK+, and omegaK0. The data were recorded with the BABAR detector and correspond to 88.9x10^6 BBbar pairs produced in e+e- annihilation at the Upsilon(4S) resonance. We find statistically significant signals for all three channels: B(B->omegapi+)=(5.4+/-1.0+/-0.5)x10^-6, B(B->omegaK+)=(5.0+/-1.0+/-0.4)x10^-6, and B(B->omegaK0)=(5.3^+1.4_-1.2+/-0.5)x10^-6. We also measure time-integrated charge asymmetries A_ch(omegapi+)=0.04+/-0.17+/-0.01 and A_ch(omegaK+)=-0.05+/-0.16+/-0.01.

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arXiv2003

Evidence for B+ --> Jpsi p Lambda-bar and Search for B0 --> Jpsi p p-bar

We have performed a search for the decays $B^+\to J/ψp \barΛ$ and $B^0\to J/psi p \bar{p}$ in a data set of $(88.9 \pm 1.0)\times 10^6$ $Υ(4S)$ decays collected by the BaBar experiment at the PEP-II $\e^+e^-$ storage ring at the Stanford Linear Accelerator Center. Four charged $B$ candidates have been observed with an expected background of $0.21\pm 0.14$ events. The corresponding branching fraction is $12^{+9}_{-6}\times 10^{-6}$, where statistical and systematic uncertainties have been combined. The result can be interpreted as a 90% confidence level (CL) upper limit of $26 \times 10^{-6}$. We also find one $B^0$ candidate, with an expected background of $0.64\pm 0.17$ events, implying a 90% CL upper limit of $1.9 \times 10^{-6}$.

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arXiv2003

A Search for B+ --> tau+ nu Recoiling Against B- --> D0 l- nu X

We present a search for the decay $B^{+} \to τ^{+} ν_τ$ in $88.9 \times 10^{6}$ $Υ(4S)$ decays recorded with the BABAR detector at the SLAC $B$-Factory. A sample of semi-exclusive, semi-leptonic B decays ($B^{-} \to D^{0} \ell^{-} \bar{ν_{\ell}}X$), where $X$ is either a photon, $π^{0}$, or nothing, is used to identify the daughter particles that are associated with the other $B$ meson in each event. These particles are searched for evidence of a one-prong leptonic $B^{+} \to τ^{+} ν_τ$ decay. For this data sample we set a preliminary upper limit on the branching fraction of $\mathcal{B}(B^{+} \to τ^{+} ν_τ) < 4.9 \times 10^{-4}$ at the 90% confidence level. This result is then combined with a statistically independent BABAR search for $B^{+} \to τ^{+} ν_τ$ to give a combined preliminary limit of $\mathcal{B}(B^{+} \to τ^{+} ν_τ) < 4.1 \times 10^{-4}$.

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arXiv2003

Branching Fractions in B -> phi h and Search for Direct CP Violation in B+- -> phi K+-

We present preliminary measurements of branching fractions of the b -> s\bar{s}s penguin-dominated decays B+ -> phi K+ and B0 -> phi K0 in a sample of approximately 89 million BBbar pairs collected by the BaBar detector at the PEP-II asymmetric-energy B-meson Factory at SLAC. We determine BF(B+ -> phi K+) = (10.0^{+0.9}_{-0.8} (stat.) \pm 0.5 (syst.)) * 10^{-6} and BF(B^0 -> phi K0) = (7.6^{+1.3}_{-1.2} (stat.) \pm 0.5 (syst.)) * 10^{-6}. Additionally, we measure the charge asymmetry A_{CP}(B+ -> phi K+) = 0.039 \pm 0.086 (stat.) \pm 0.011 (syst.) and set an upper limit on the CKM- and color-suppressed decay B+ -> phi pi+, BF(B+ -> phi pi+) < 0.41 * 10^{-6} (90% CL).

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arXiv2003

Observation of the Decay $B^{\pm} \to π^{\pm}π^{0}$, Study of $B^{\pm} \to K^{\pm}π^{0}$, and Search for $B^{0} \to π^{0}π^{0}$

We present results for the branching fractions and charge asymmetries in $B^{\pm} \to h^{\pm} π^{0}$ (where $h^{\pm} = π^{\pm}, K^{\pm}$) and a search for the decay $B^{0} \to π^{0} π^{0}$ using a sample of approximately 88 million $B\bar{B}$ pairs collected by the BABAR detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. We measure ${\cal B} (B^{\pm} \to π^{\pm} π^{0}) = (5.5 ^{+1.0}_{-0.9} \pm 0.6) \times 10^{-6}$, where the first error is statistical and the second is systematic. The $B^{\pm} \to π^{\pm} π^{0}$ signal has a significance of $7.7 σ$ including systematic uncertainties. We simultaneously measure the $K^{\pm}π^{0}$ branching fraction to be $ {\cal B} (B^{\pm} \to K^{\pm} π^{0}) = (12.8 ^{+1.2}_{-1.1} \pm 1.0) \times 10^{-6}$. The charge asymmetries are ${\cal A}_{π^{\pm}π^{0}} = -0.03_{-0.17}^{+0.18} \pm 0.02$ and ${\cal A}_{K^{\pm}π^{0}} = -0.09 \pm 0.09 \pm 0.01$. We place a 90% confidence-level upper limit on the branching fraction ${\cal B} (B^{0} \to π^{0} π^{0})$ of $3.6 \times 10^{-6} $.

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arXiv2003

Measurements of the Branching Fractions of Charged B Decays to K+ pi- pi+ Final States

We present preliminary results of searches for exclusive charged-B decays to K+ pi- pi+ from 61.6 million BBbar pairs collected at the Upsilon(4S) resonance with the BaBar detector at the SLAC PEP-II asymmetric B Factory. The Dalitz plot is divided into eight regions and, using a maximum-likelihood fit, we measure statistically significant yields in all regions. We interpret the results as the following branching fractions averaged over charged--conjugate states: B+ --> K*0 pi+, K*0 --> K+ pi- = (10.3 +/- 1.2 +1.0 -2.7) x 10^-6, B+ --> f0 K+, f_0 --> pi+ pi- = (9.2 +/- 1.2 +2.1 -2.6) x 10^-6, B+ --> chi_c0 K+, chi_c0 --> pi+ pi- = (1.46 +/- 0.35 +/- 0.12) x 10^-6 and B+ --> D0bar pi+, D0bar --> K+ pi- = (184.6 +/- 3.2 +/- 9.7) x 10^-6. The first uncertainty is statistical and the second is systematic and includes resonance--model and interference uncertainties. We give 90% confidence upper limits on the branching fractions of the following channels: B+ --> rho K+ < 6.2 x 10^-6 and B+ --> K+ pi- pi+ non-resonant < 17 x 10^-6.

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arXiv2003

Rates, Polarizations, and Asymmetries in Charmless Vector-Vector B Decays

With a sample of approximately 89 million BBbar pairs collected with the BABAR detector, we measure branching fractions, determine the degree of longitudinal polarization, and search for direct CP violation in the decays B0=>phiK*0 and B+=>phiK*+. We perform a search for other charmless vector-vector B decays involving rho and K*(892) resonances and observe the decays B+=>rho0K*+ and B+=>rho0rho+. The branching fractions are measured to be BR(phiK*0)=(11.1^{+1.3}_{-1.2}\pm 1.1)10^{-6}, BR(phiK*+)=(12.1^{+2.1}_{-1.9}\pm 1.5)10^{-6}, BR(rho0K*+)=(7.7^{+2.1}_{-2.0}\pm 1.4)10^{-6}, and BR(rho0rho+)=(9.9^{+2.6}_{-2.5}\pm 2.5)10^{-6}. The longitudinal polarization fractions are measured to be GammaL/Gamma(phiK*0)=0.65\pm 0.07\pm 0.04 and GammaL/Gamma(phiK*+)=0.46\pm 0.12\pm 0.05. We measure the charge asymmetries: ACP(phiK*0)=+0.04\pm 0.12\pm 0.02 and ACP(phiK*+)=+0.16\pm 0.17\pm 0.04.

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arXiv2003

Study of Time-Dependent CP Asymmetry in Neutral B Decays to J/psi pi0

We present the first study of the time-dependent CP-violating asymmetry in B0 -> J/psi pi0 decays using e+e- annihilation data collected with the BaBar detector at the Upsilon(4S) resonance during the years 1999-2002 at the PEP-II asymmetric-energy B Factory at SLAC. Using approximately 88 million BBbar pairs, our results for the coefficients of the cosine and sine terms of the CP asymmetry are C_(J/psi pi0) = 0.38 +/- 0.41 (stat) +/- 0.09 (syst) and S_(J/psi pi0) = 0.05 +/- 0.49 (stat) +/- 0.16 (syst).

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arXiv2003

Measurement of B0->D_s()+D- Branching Fractions and B0->D_s+D- Polarization with a Partial Reconstruction Technique

We present a study of the decays B0->D_s(*)+D*-, using 20.8 fb-1 of e+e- annihilation data recorded with the BABAR detector. The analysis is conducted with a partial reconstruction technique, in which only the D_s(*)+ and the soft pion from the D*- decay are reconstructed. We measure the branching fractions BR(B0->D_s+D*-) = (1.03 +/- 0.14 +/- 0.13 +/- 0.26)% and BR(B0->D_s*+D*-) = (1.97 +/- 0.15 +/- 0.30 +/- 0.49)%, where the first error is statistical, the second is systematic, and the third is the error due to the D_s+->phi pi+ branching fraction uncertainty. From the B0->D_s*+D*- angular distributions, we measure the fraction of longitudinal polarization Gamma_L/Gamma = (51.9 +/- 5.0 +/- 2.8)%, which is consistent with theoretical predictions based on factorization.

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arXiv2003

Search for the decay B^0 --> gamma-gamma

We present a limit on the branching fraction for the decay $B^0 \to γγ$ using data collected at the $Υ(4S)$ resonance with the BABAR detector at the PEP-II asymmetric--energy $e^+e^-$ collider. Based on the observation of one event in the signal region, out of a sample of $21.3 \times 10^6$ $e^+e^- \to Υ(4S) \to B\bar B$ decays, we establish an upper limit on the branching fraction of ${\cal B}(B^0 \to γγ) < 1.7 \times 10^{-6}$ at the 90% confidence level. This result substantially improves upon existing limits.

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