arXiv subjects
Publications and source records attributed to B. Aubert.
We report first observations of the decays B- to Ds(*)+ K- pi-, using 292 fb^-1 of data collected at Upsilon(4S) resonance energy by the BaBar detector at the PEP II e+ e- collider. The branching fractions are measured to be B(B- to Ds+ K- pi-) = (1.88 +- 0.13 +- 0.41) x 10^-4 and B(B- to Ds*+ K- pi-) = (1.84 +- 0.19 +- 0.40) X 10^-4.
A search for the decay B+ -> a0+pi0 with the a0+ decaying to an eta and a pi+ was carried out at the Stanford Linear Accelerator Center using the BABAR detector coupled with the PEP-II collider. The analysis used a data sample comprised of approximately 252 million BBbar pairs collected at the Upsilon(4S) resonance. No signal was observed and a 90% confidence level upper limit on the branching fraction was set at 1.32 x 10^{-6}.
We search for decays of a B meson into a neutral D meson and a kaon, with the D meson decaying into K+pi-pi0. This final state can be reached through the b --> c transition B- -> D0K- followed by the doubly Cabibbo-suppressed D0 --> K+pi-pi0, or the b --> u transition B- --> D0bar K- followed by the Cabibbo-favored D0bar --> K+ pi-pi0. The interference of these two amplitudes is sensitive to the angle gamma of the unitarity triangle. We present preliminary results based on 226 10^{6} e+e- --> Y(4s) --> BBbar events collected with the BABAR detector at SLAC. We find no significant evidence for these decays and we set a limit R_ADS =(BR(B- -->[K+pi-pi0]_D K-)+ BR(B- --> [K-pi+pi0]_D K+))/(BR(B- -->[K-pi+pi0]_D K-)+ BR(B- --> [K+pi-pi0]_D K+))<0.039 at 95% confidence level, which we translate with a Bayesian approach into r_B = |A(B- --> D0bar K-)|/|A(B- --> D0bar K-)| < 0.185 at 95% confidence level.
We report preliminary measurements of the exclusive charmless semileptonic branching fractions of the B+ --> eta l+ nu and B+ --> eta' l+ nu decays. These measurements are based on 316 fb-1 of data collected at the Y(4S) resonance by the BABAR detector. In events in which the decay of one B meson to a hadronic final state is fully reconstructed, the semileptonic decay of the recoiling B meson is identified by the detection of a charged lepton and an eta or eta'. We measure the branching fraction BR(B+ --> eta l+ nu) = (0.84 +/- 0.27 +/- 0.21) x 10-4, where the first error is statistical and the second one systematic. We also set an upper limit on the branching fraction of BR(B+ --> eta l+ nu) < 1.4 x 10-4 and BR(B+ --> eta' l+ nu) < 1.3 x 10^-4 at the 90% confidence level.
We present a study of B semileptonic decays into charm final states based on 211.7 fb^{-1} of data collected at the Υ(4S) resonance with the babar detector at the pep2 e^+e^- storage ring. Using a novel technique based on the simultaneous fit of a set of variables reconstructed on the recoil of a B tagged in an hadronic decay mode, we measure the relative branching fractions Γ(B^- \to D^0\ell^- \barν_{\ell}) / Γ(B^- \to D X \ell^- \barν_{\ell}) = 0.210 \pm 0.017 (stat.) \pm 0.021 (syst.), Γ(B^- \to D^{*0}\ell^- \barν_{\ell}) / Γ(B^- \to D X \ell^- \barν_{\ell}) = 0.611 \pm 0.022 (stat.) \pm 0.027 (syst.) and Γ(B^- \to D^{**0}(D^{(*)}π)\ell^- \barν_{\ell}) / Γ(B^- \to D X \ell^- \barν_{\ell}) = 0.173 \pm 0.017 (stat.) \pm 0.021 (syst.) .
We search for B0 meson decays into two-body combinations of K0, eta, eta', and phi mesons in 324 million B Bbar pairs collected with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We measure the following branching fractions (upper limits at 90% confidence level) in units of 10^{-6}: Br(B0->eta K0) =1.8+0.7-0.6 +-0.1(2.9), Br(B0->eta eta)=1.1+0.5-0.4 +-0.1(1.8), Br(B0->eta phi)=0.1+-0.2 +-0.1(0.6), Br(B0->eta' phi)=0.2+0.4-0.3 +-0.1(1.0), Br(B0->eta' eta')=1.0+0.8-0.6 +-0.1(2.4), where the first error is statistical and the second systematic.
The photon spectrum in B -> X_s gamma decay, where X_s is any strange hadronic state, is studied using a data sample of 88.5 million e+e- -> Upsilon(4S) -> BBbar decays collected by the BaBar experiment at SLAC. The partial branching fraction, Delta B(B -> X_s gamma)=(3.67 +- 0.29(stat.) +- 0.34(sys.) +- 0.29(model)) times 10^-4, the first moment =2.288 +- 0.025 +- 0.017 +- 0.015 GeV and the second moment - ^2 =0.0328 +- 0.0040 +- 0.0023 +- 0.0036 GeV^2 are measured for the photon energy range 1.9 GeV < E_gamma < 2.7 GeV. They are also measured for narrower E_gamma ranges. The moments are then fit to recent theoretical calculations to extract the Heavy Quark Expansion parameters, m_b and mu_pi^2, and to extrapolate the partial branching fraction to E_gamma>1.6 GeV. In addition, the direct CP asymmetry A_CP(B -> X_(s+d) gamma) is measured to be -0.110 +- 0.115(stat.) +- 0.017(sys.).
We search for rare FCNC charm decays of the form $X_c^+\to h^+\llp$, where $X_c^+$ is a charm hadron, $h$ is a pion, kaon or proton, and $\ell^{(}{'}^{)}$ is an electron or a muon. In the pion and kaon modes, we study both $D^+$ and $D_s^+$ decays, while in the proton modes we study $Λ_c^+$ decays. Based on a data sample of 288${fb}^{-1}$ of $e^+e^-$ collisions collected by BABAR, we set preliminary 90% confidence level limits between 4 to 40$\times10^{-6}$ for the branching fractions of the different decay modes. For most decay modes, our analysis provides a significant improvement over previous results.
We present preliminary results from a search for inclusive charmless B->KX decays. These decays occur dominantly via one-loop b->s penguin transitions, and can provide useful information about these processes. Using a sample of 288.5/fb collected with the BABAR detector at the PEP-II asymmetric-energy e+e- B Factory at SLAC, we search for high-energy kaons recoiling against fully reconstructed B decays. We measure the partial branching fractions for kaons with momentum p*(K)>2.34GeV in the B rest frame, and obtain (in units of 10^-6): B(B->K+X, p*>2.34GeV) = 196^{+37}_{-34}(stat.)^{+31}_{-30}(syst.) and B(B->K0X, p*>2.34GeV) = 154^{+55}_{-48}(stat.)^{+55}_{-41}(syst.) (<266 at 90% C.L.).
We present studies of two-body and three-body charmed baryonic B decays in a sample of 232 million $B\bar{B}$ pairs collected with the BABAR detector at the PEP-II $e^+e^-$ storage ring. The branching fractions of the decays $\bar{B}^{0} \to Λ_{c}^{+} \bar{p}$ and $B^{-} \to Λ_{c}^{+} \bar{p} π^{-}$ are measured to be $(2.15 \pm 0.36 \pm 0.13 \pm 0.56) \times 10^{-5}$ and $(3.53 \pm 0.18 \pm 0.31 \pm 0.92)\times10^{-4}$, respectively. The uncertainties quoted are statistical, systematic, and from the $Λ_{c}^{+} \to p K^- π^+$ branching fraction. We observe a baryon-antibaryon threshold enhancement in the $Λ_{c}^{+} \bar{p}$ invariant mass spectrum of the three-body mode and measure the ratio of the branching fractions to be ${\cal B}(B^{-} \to Λ_{c}^{+} \bar{p} π^{-})/{\cal B}(\bar{B}^{0} \to Λ_{c}^{+} \bar{p}) = 16.4 \pm 2.9 \pm 1.4$. These results are preliminary.
With the BaBar detector at the PEP-II asymmetric $B$ Factory at SLAC, we present the first search for the decays $B^0\to\ell^+\ell^-γ$ ($l=e, μ$). Using a data set of 292 $fb^{-1}$ collected at the $Υ(4S)$ resonance, we find no significant signal and set the following branching fraction upper limits at 90% confidence level: $\mathcal{B}(B^0\to e^+e^-γ)<0.7\times 10^{-7}$ and $\mathcal{B}(B^0\to μ^+μ^-γ)<3.4\times 10^{-7}$.
We report the results of a study of the exclusive charmless semileptonic B0->pilnu decay undertaken with approximately 227 million BBbar pairs collected at the Upsilon(4S) resonance with the BABAR detector. The analysis uses events in which the signal B mesons are reconstructed with a novel loose neutrino reconstruction technique. We obtain partial branching fractions in 12 bins of q2, the l+nu invariant mass squared, from which we extract the f+(q2) form factor shape and the total branching fraction: BF(B0->pilnu) = (1.44 +- 0.08(stat) +- 0.10(syst))x 10-4. Based on a recent theoretical calculation of the form factor, we find the magnitude of the CKM matrix element |Vub| to be (4.1 +- 0.2(stat) +- 0.2(syst) +0.6-0.4(FF))x 10-3, where the last uncertainty is due to the normalization of the form factor.
In a study of B+ --> J/psi gamma K+ decays, we find evidence for the radiative decay X(3872) --> J/psi gamma with a statistical significance of 3.4 sigma. We measure the product of branching fractions BF(B+ --> X(3872) K+).BF(X(3872) --> J/psi gamma) = (3.3 +/- 1.0 +/- 0.3) x 10^-6, where the uncertainties are statistical and systematic, respectively. We also measure the branching fraction BF(B+ --> chi_c1 K+) = (4.9 +/- 0.2 +/- 0.4) x 10^-4. These results are obtained from (287+/-3) million BBar decays collected at the Y(4S) resonance with the BaBar detector at the PEP-II B Factory at SLAC.
We report searches for B-meson decays to the charmless final states rho K* and f0(980) K* with a sample of 232 million BBbar pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We measure the following branching fractions in units of 10^{-6}: B (B+ --> rho0 K*+) = 3.6 +/- 1.7 +/- 0.8 (< 6.1), B (B+ --> rho+ K*0) = 9.6 +/- 1.7 +/- 1.5, B (B0 --> rho- K*+) = 5.4 +/- 3.6 +/- 1.6 (< 12.0), B (B0 --> rho0 K*0) = 5.6 +/- 0.9 +/- 1.3, B (B+ --> f0(980) K*+) = 5.2 +/- 1.2 +/- 0.5, and B (B0 --> f0(980) K*0) = 2.6 +/- 0.6 +/- 0.9 (< 4.3). The first error quoted is statistical, the second systematic, and the upper limits, in parentheses, are given at the 90% confidence level. For the statistically significant modes we also measure the fraction of longitudinal polarization and the charge asymmetry: f_L (B+ --> rho+ K*0) = 0.52 +/- 0.10 +/- 0.04, f_L (B0 --> rho0 K*0) = 0.57 +/- 0.09 +/- 0.08, A_CP (B+ --> rho+ K*0) = -0.01 +/- 0.16 +/- 0.02, A_CP (B0 --> rho0 K*0) = 0.09 +/- 0.19 +/- 0.02, A_CP (B+ --> f_0(980) K*+) = -0.34 +/- 0.21 +/- 0.03, and A_CP (B0 --> f_0(980) K*0) = -0.17 +/- 0.28 +/- 0.02.
We have searched for the violation of baryon number B and lepton number L in the (B-L)-conserving modes tau- -> anti-Lambda0 pi- and tau- -> anti-Lambda0 K- as well as the (B-L)-violating modes tau- -> Lambda0 pi- and tau- -> Lambda0 K- using 237 inv. fb of data collected with the BABAR detector at the PEP-II asymmetric-energy e+e- storage ring. We do not observe any signal and determine preliminary upper limits on the branching fractions B(tau- -> anti-Lambda0 pi-) < 5.9 x 10^-8, B(tau- -> Lambda0 pi-) < 5.8 x 10^-8, B(tau- -> anti-Lambda0 K-) < 7.2 x 10^-8, and B(tau- -> Lambda0 K-) < 15 x 10^-8 at 90% confidence level.
We present the preliminary results from the search of the non-conservation of lepton flavor number in the decay of a $τ$ to a lighter mass lepton and a pseudo-scalar meson, performed using $e^+e^- \to τ^+τ^-$ events collected at a center-of-mass energy near 10.58 GeV with the BABAR detector at the SLAC PEP-II $e^+e^-$ storage ring. No evidence of such a signal has been found in the data sample corresponding to a luminosity of 314.5 fb$^{-1}$, and we set an upper limit of $1.6\times 10^{-7}$ at 90% confidence level on the decay of $τ^- \to μ^-η$.
We present results of a search for the rare flavor-changing neutral-current decay B --> pi l+ l-, based on a data sample corresponding to 209 fb-1 of integrated luminosity collected with the BABAR detector at the PEP-II B Factory. We reconstruct the four exclusive B decay modes B+ --> pi+ l+ l- and B0 --> pi0 l+ l-, where l is either an e or mu. We find no evidence for a signal, and we obtain the upper limit at 90% confidence level on the lepton-flavor--averaged branching fraction to be BF(B+ --> pi+ l+ l-) = 2 x tau_B+/tau_B0 x BF(B0 --> pi0 l+ l-) < 7.9 x 10-8. We also obtain an upper limit at 90% confidence level on the lepton-flavor--violating decay B --> pi e mu of BF(B --> pi e mu) < 9.8 x 10-8.
The Xi(1690)0 resonance is observed in the Lambda anti-K0 channel in the decay Lambdac+ --> Lambda anti-K0 K+, from a data sample corresponding to a total integrated luminosity of ~ 200 fb-1 recorded by the Babar detector at the PEPII asymmetric-energy e+ e- collider operating at ~ 10.58 GeV and ~ 10.54 GeV center-of-mass energies. A fit to the Dalitz plot intensity distribution corresponding to the coherent superposition of amplitudes describing Lambda a0(980)+ and Xi(1690)0 K+ production yields mass and width values of 1684.7 +/- 1.3 (stat.) +2.2 -1.6 (syst.) MeV/c2, and $8.1 +3.9 -3.5 (stat.) +1.0 -0.9 (syst.) MeV, respectively, for the Xi(1690)0, while the spin is found to be consistent with value of 1/2 on the basis of studies of the (Lambda KS) angular distribution.