arXiv subjects

B. Aubert

Publications and source records attributed to B. Aubert.

At least 523 records · Page 29Linked to original sources

arXiv2003

Measurement of Branching Fractions and Charge Asymmetries in B Meson Decays to eta(') K*, eta{'} rho, and eta' pi

We present preliminary measurements of branching fractions and charge asymmetries for the B meson decays B -> eta(')K*, B -> eta(')rho, and B+ -> eta' pi+. The data were recorded with the BaBar detector at PEP-II and correspond to 89 x 10^6 B B-bar pairs produced in e+e- annihilation through the Upsilon(4S) resonance. We find the branching fractions B(B0 -> eta K*0) = (19.0 +2.2 -2.1 +/- 1.3) x 10^-6, B(B+ -> eta K*+) = (25.7 +3.8 -3.6 +/- 1.8) x 10^-6, B(B+ -> eta rho+) = (10.5 +3.1 -2.8 +/- 1.3) x 10^-6, B(B+ -> eta' rho+) = (14.0 +5.1 -4.6 +/- 1.9) x 10^-6 (< 22 x 10^-6 with 90% confidence), and B(B+ -> eta' pi+) = (2.8 +1.3 -1.0 +/- 0.3) x 10^-6 (< 4.5 x 10^-6). We also set 90% CL upper limits of B(B0 -> eta' K*0) < 6.4 x 10^-6 and B(B+ -> eta' K*+) < 12 x 10^-6. The time-integrated charge asymmetries are Ach(eta K*0) = +0.03 +/- 0.11 +/- 0.02, Ach(eta K*+) = +0.15 +/- 0.14 +/- 0.02, and Ach(eta rho+) = +0.06 +/- 0.29 +/- 0.02.

hep-ex↗

arXiv2003

Measurement of the B --> Xs l+ l- Branching Fraction Using a Sum over Exclusive Modes

We present a measurement of the branching fraction for the flavor-changing neutral current process B --> Xs l+ l- based on a sample of 88.9 \times 10^6 Upsilon(4S) --> BBbar events recorded with the BaBar detector at the PEP-II e+e- storage ring. The final state is reconstructed from pairs of electrons or muons and a hadronic system consisting of one K+/- or K0s and up to two pions, with at most one pi0. Summing over both lepton flavors, we observe a signal of 41 +/- 10(stat) +/- 2(syst) events with a statistical significance of 4.6 sigmas. The inclusive branching fraction is determined to be BF(B --> Xs l+ l-) = [6.3 +/- 1.6(stat) +1.8 -1.5(syst)] 10^{-6} for m(l+ l-) > 0.2 GeV/c^2. All results are preliminary.

hep-ex↗

arXiv2003

Measurement of BR(B0 -> Ds+D-) and Determination of the Ds+ -> phi pi+ Branching Fraction with a Partial-Reconstruction Method

We present model-independent measurements of the branching fractions ${\cal B}(B^0\to D_s^{*+} D^{*-})$ and ${\cal B}(D_s^+ \to ϕπ^+)$ based on 19.3 $\textup{fb}^{-1}$ of data collected by the $BABAR$ detector at the PEP-II $e^+e^-$ $B$ Factory. Neutral $B$-meson decays to the $D_s^{*+}D^{*-}$ final state are selected with a partial reconstruction of the $D_s^{*+}$; that is, only the $D^{*-}$ and the soft photon from the decay $D_s^{*+} \to \Ds γ$ are reconstructed. The branching fraction ${\cal B}(B^0\to D_s^{*+} D^{*-})$ is extracted from these event yields, while ${\cal B}(D_s^+ \to ϕπ^+)$ is determined by combining this result with a previous measurement of the product ${\cal B}(B^0\to D_s^{*+} D^{*-}) \times {\cal B}(D_s^+ \to ϕπ^+)$ with partial reconstruction of the $D^{*-}$. We obtain the following preliminary results: ${\cal B}(B^0\to D_s^{*+} D^{*-}) = (1.50 \pm 0.16 \pm 0.12)%,$ ${\cal B}(D_s^+ \to ϕπ^+) = (4.7 \pm 0.6 \pm 0.8)%$ where the first error is statistical, and the second systematic.

hep-ex↗

arXiv2003

Observation of the Decay $B^{0} \to π^{0}π^{0}$

We present an observation of the decay $B^{0} \to π^{0} π^{0}$ based on a sample of 124 million $B\bar{B}$ pairs recorded by the BABAR detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. We observe $46 \pm 13 \pm 3$ events, where the first error is statistical and the second is systematic, corresponding to a significance of 4.2 standard deviations including systematic uncertainties. We measure the branching fraction $\BR(B^{0} \to π^{0} π^{0}) = (2.1 \pm 0.6 \pm 0.3) \times 10^{-6}$, averaged over $B^{0}$ and $\bar{B}^{0}$ decays.

hep-ex↗

arXiv2003

Measurement of Branching Fractions and CP-Violating Charge Asymmetries in B+ --> rho+ pi0 and B+ --> rho0 pi+, and Search for B0 --> rho0 pi0

We present preliminary measurements of branching fractions and CP-violating charge asymmetries in B-meson decays to rho pi. The data sample comprises 89 million Y(4S) --> BBbar decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We find the charge-averaged branching fractions B(B+ --> rho+ pi0) = (11.0 +/- 1.9(stat.) +/- 1.9(syst.)) * 10^-6 and B(B+ --> rho0 pi+) = (9.3 +/-1.0(stat.) +/- 0.8(syst.)) * 10^-6; we set a 90% confidence-level upper limit of B(B0 --> rho0 pi0) < 2.5 * 10^-6. We measure the CP-violating charge asymmetries A_CP(rho+ pi0) = 0.23 +/- 0.16(stat.) +/- 0.06(syst.) and A_CP(rho0 pi+) = -0.17 +/- 0.11(stat.) +/- 0.02(syst.).

hep-ex↗

arXiv2003

Measurements of the Branching Fractions and Bounds on the Charge Asymmetries of Charmless Three-Body Charged B Decays

We present measurements of branching fractions and charge asymmetries for charmless B-meson decays to three-body final states of charged pions and kaons. The analysis uses 81.8 fb^-1 of data collected at the Upsilon(4S) resonance with the BaBar detector at the SLAC PEP-II asymmetric B Factory. We measure the branching fractions B(B+ -> pi+ pi- pi+) = (10.9 +/- 3.3 +/- 1.6) x 10^-6, B(B+ -> K+ pi- pi+) = (59.1 +/- 3.8 +/- 3.2) x 10^-6, and B(B+ -> K+ K- K+) = (29.6 +/- 2.1 +/- 1.6) x 10^-6, and provide 90% C.L. upper limits for other decays. We observe no charge asymmetries for these modes.

hep-ex↗

arXiv2003

Limits on D0-D0bar Mixing and CP Violation from the Ratio of Lifetimes for Decay to K-pi+, K-K+, and pi-pi+

We present a measurement of $D^0$-$\D0bar$ mixing parameters using the ratios of lifetimes extracted from samples of $D^0$ mesons decaying to $K^-π^+$, $K^-K^+$, and $π^-π^+$. Using 91 ${\rm fb}^{-1}$ of data collected by the BaBar detector at the PEP-II asymmetric-energy $B$ Factory, we obtain a value $Y = (0.8 \pm 0.4 ({\rm stat.}) {}^{+0.5}_{-0.4} ({\rm syst.}))$%, which, in the limit of CP conservation, corresponds to the mixing parameter $y = ΔΓ/2Γ$. Using the difference in lifetimes of $D^0$ and $\D0bar$ mesons, we obtain the CP-violation parameter $ΔY = (-0.8 \pm 0.6 ({\rm stat.}) \pm 0.2 ({\rm syst.}))$%.

hep-ex↗

arXiv2003

Measurement of the Inclusive Charmless Semileptonic Branching Ratio of B Mesons and Determination of |V_ub|

We report a measurement of the inclusive charmless semileptonic branching fraction of B mesons in a sample of 89 million BBbar events recorded with the BABAR detector at the Y(4S) resonance. Events are selected by fully reconstructing the decay of one B meson and identifying a charged lepton from the decay of the other B meson. The number of signal events is extracted from the hadronic mass distribution and is used to determine the ratio of branching fractions BR(B->Xulnu)/BR(B->Xlnu) = (2.06 +/-0.25(stat) +/-0.23(syst) +/-0.36(theo)) x 10^{-2}. Using the measured branching fraction for inclusive semileptonic B decays, we find BR(B->Xulnu) = (2.24 +/- 0.27(stat) +/- 0.26(syst) +/- 0.39(theo)) x 10^{-3} and derive the CKM matrix element |Vub| = (4.62 +/- 0.28(stat) +/- 0.27(syst) +/- 0.48 (theo)) x 10^{-3}.

hep-ex↗

arXiv2003

Measurement of the First and Second Moments of the Hadronic Mass Distribution in Semileptonic B Decays

We report a preliminary measurement of the first and second moments of the hadronic mass distributions in B --> X_c lv decays. The measurements are based on Upsilon (4S) --> BBbar events where the hadronic decay of one of the B mesons is fully reconstructed and a charged lepton from the decay of the other B meson is identified. The moments are presented for threshold lepton momenta ranging from 0.9 to 1.6 GeV. From the $ $ moments we determine the non-perturbative Heavy Quark Expansion (HQE) parameters, $\barΛ$ and $λ_1$. We combine the measured moments $ $ with earlier BABAR measurements of the semileptonic branching ratios and B lifetimes and perform a simultaneous fit to the HQE for the moments obtained for different threshold lepton momenta and the semileptonic decay width. This fit results in an improved value for the CKM matrix element $|V_{cb}|$.

hep-ex↗

arXiv2003

A Search for B+ to mu+ nu_mu

We have performed a search for the leptonic B decay B+ --> mu+ nu_mu with data collected at the Upsilon(4S) resonance by the BABAR experiment at the PEP-II storage ring. With an integrated luminosity of approximately 81.4 fb-1 (88.4 million BBbar pairs), we find no convincing evidence for a signal and set a preliminary upper limit on the branching fraction of BR(B+ --> mu+ nu_mu) < 6.6 x 10^{-6} at the 90% confidence level.

hep-ex↗

arXiv2003

Evidence for the Rare Decay B -> J/psi eta K

We report evidence for the $B$ meson decays, $B^\pm\to J/ψηK^\pm$ and $B^0\to J/ψηK^0_S$, using {90} million $B\bar B$ events collected at the $\ensuremath{Υ{(4S)}}$ resonance with the \babar detector at the PEP-II $e^+ e^-$ asymmetric-energy storage ring. We obtain preliminary branching fractions in the charged and neutral channels of $(10.8\pm 2.3(stat.)\pm 2.4(syst.))\times 10^{-5}$ and $(8.4\pm 2.6(stat.)\pm 2.7(syst.))\times 10^{-5}$, respectively.

hep-ex↗

arXiv2003

Study of Time-Dependent CP Asymmetries with Partial Reconstruction of B -> D*+ pi-

We present a preliminary measurement of the time-dependent CP asymmetries in decays of neutral B mesons to the final states D*pi using approximately 82 million BBbar events collected by the BaBar experiment at the PEPII storage ring. Events containing these decays are selected with a partial reconstruction technique, in which only the high momentum pion and the low momentum pion from the D* decay are reconstructed. The flavor of the other B meson in the event is tagged using the information from kaon and lepton candidates. We measure the time-dependent CP asymmetry A = -0.063 +/- 0.024 (stat.) +/- 0.017 (syst.). We interpret these results in terms of the angles of the unitarity triangle to set a bound on |sin(2 beta + gamma)|.

hep-ex↗

arXiv2003

Measurement of Time-Dependent CP Asymmetries and the CP-Odd Fraction in the Decay B0 --> D+D-

We present a measurement of time-dependent CP asymmetries and an updated determination of the CP-odd fraction in the decay B0 --> D*+D*- using a data sample of 88 x 10^6 BBbar pairs collected by the BABAR detector at the PEP-II B Factory at SLAC. We determine the CP-odd fraction to be 0.063 +/- 0.055(stat) +/- 0.009(syst). The time-dependent CP asymmetry parameters $Im(λ_+)$ and $|λ_+|$ are determined to be 0.05 +/- 0.29(stat) +/- 0.10(syst) and 0.75 +/- 0.19(stat) +/- 0.02(syst), respectively. The Standard Model predicts these parameters to be -sin2beta and 1, respectively, in the absence of penguin diagram contributions.

hep-ex↗

arXiv2003

Measurement of the Branching Fraction and CP-violating Asymmetries in Neutral B Decays to D*+-D-+

We present measurements of the branching fraction and CP-violating asymmetries for neutral B decays to D*+-D-+. The measurement uses a data sample of approximately 88 million Y(4S) --> B Bbar decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. We measure the branching fraction to be (8.8 +- 1.0 +- 1.3) x 10^-4 and the time-integrated CP-violating asymmetry between the rates to D*+D- and D*-D+ to be A = -0.03 +- 0.11 +- 0.05. We also measure the time-dependent CP-violating asymmetry parameters to be S-+ = -0.24 +- 0.69 +- 0.12, C-+ = -0.22 +- 0.37 +- 0.10 for B --> D*-D+ and S+- = -0.82 +- 0.75 +- 0.14$, C+- = -0.47 +- 0.40 +- 0.12 for B --> D*+D-. In each case the first error is statistical and the second error is systematic.

hep-ex↗

arXiv2003

Search for the Radiative Decays B -> rho gamma and B0 -> omega gamma

A search for the exclusive radiative decays B --> rho(770) gamma and B0 --> omega(782) gamma is performed on a sample of about 84\times 10^{6} B\bar B events collected by the BaBar detector at the PEP-II asymmetric-energy e+e- storage ring. No significant signal is seen in any of the channels. We set upper limits on the branching fractions of BR(B^0 -> rho^0 gamma) < 1.2 \times 10^{-6}, BR(B^+ -> rho^+ gamma) < 2.1 \times 10^{-6}, and BR(B^0 -> omega gamma) < 1.0 \times 10^{-6} at 90% confidence level (C.L.). Using the assumption that Gamma(B --> rho gamma) = Gamma(B+ --> rho+ gamma) =2\timesΓ(B0 --> rho0 gamma), we find the combined limit BR(B --> rho gamma)<1.9 \times 10^{-6}, corresponding to BR(B --> rho gamma)/\BR(B --> K* gamma) < 0.047 at 90% C.L.

hep-ex↗

arXiv2003

Measurements of Branching Fractions and CP-Violating Asymmetries in B0 -> rho+- h-+ Decays

We present measurements of branching fractions and CP-violating asymmetries in B0 -> rho+- pi-+ and B0 -> rho- K+ decays. The results are obtained from a data sample of 88.9 10^6 Upsilon(4S) -> B Bbar decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. From a time-dependent maximum likelihood fit we measure the charge-averaged branching fractions B(B0 -> rho+- pi-+) = (22.6 +- 1.8(stat) +- 2.2(syst)) 10^(-6) and B(B0 -> rho- K+) = (7.3 +1.3 -1.2 +- 1.3) 10^(-6); and the CP-violating charge asymmetries Acp(rho pi) = -0.18 +- 0.08 +- 0.03 and Acp(rho K) = 0.28 +- 0.17 +- 0.08; the direct CP violation parameter C(rho pi) = 0.36 +- 0.18 +- 0.04 and the mixing-induced CP violation parameter S(rho pi) = 0.19 +- 0.24 +- 0.03; and the dilution parameters dC(rho pi) = 0.28 +0.18 -0.19 +- 0.04 and dS(rho pi) = 0.15 +- 0.25 +- 0.03.

hep-ex↗

arXiv2003

A Study of Time-Dependent CP Asymmetry in B0 --> J/psi pi0 Decays

We present our 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 Y(4S) resonance during the years 1999--2002 at the PEP-II asymmetric-energy B Factory at SLAC. With about 88 million B Bbar pairs, our preliminary 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).

hep-ex↗

arXiv2003

Measurement of the Branching Fractions for the Exclusive Decays of B^0 and B^+ to Dbar^()D^()K

We report the observation of 823+/-57 B^0 and 970+/-65 B^+ decays to doubly charmed final states Dbar^(*)D^(*)K, where Dbar^(*) and D^(*) are fully reconstructed and K is either a K+/- or a K^0. We use a sample of 82.3+/- 0.9 million BBbar events collected between 1999 and 2002 with the babar detector at the PEP-II storage ring at the Stanford Linear Accelerator Center. The 22 possible B decays to Dbar^(*)D^(*)K are reconstructed exclusively and the corresponding branching fractions or limits are determined. The branching fractions of the B^0 and of the B^+ to Dbar^(*)D^(*)K$ are found to be BR(B^0 --> Dbar^(*) D^(*) K) = (4.3 +/- 0.3 stat +/- 0.6 syst)%, BR(B^+ --> Dbar^(*) D^(*) K) = (3.5 +/- 0.3 stat +/- 0.5 syst)%. A search for decays to orbitally excited $D_s$ states, B --> Dbar^(*) D_{sJ}^{+} (D_{sJ}^{+} --> D^(*)0K^+) is also performed.

hep-ex↗