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The BABAR Collaboration

Publications and source records attributed to The BABAR Collaboration.

At least 361 records · Page 20Linked to original sources

arXiv2006

Measurement of the Pseudoscalar Decay Constant fDs Using Charm-Tagged Events in e+e- Collisions at \sqrt{s}=10.58GeV

Using 230.2 fb^(-1) of e+e- annihilation data collected with the BABAR detector at and near the peak of the Y(4S) resonance, 489 +/- 55 events containing the pure leptonic decay D_s^+ --> mu^+ nu_mu have been isolated in charm-tagged events. The ratio of partial widths Gamma(D_s^+ --> mu^+ nu_mu)/Gamma(D_s^+ --> phi pi^+) is measured to be 0.143 +/- 0.018 +/- 0.006 allowing a determination of the pseudoscalar decay constant f_{D_s} = (283 +/- 17 +/- 7 +/- 14) MeV. The errors are statistical, systematic, and from the D_s^+ --> phi pi^+ branching ratio, respectively.

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arXiv2006

Determination of the Form Factors for the Decay B0 --> D*-l+nu_l and of the CKM Matrix Element |Vcb|

We present a combined measurement of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}|$ and of the parameters $ρ^2$, $R_1$, and $R_2$, which fully characterize the form factors of the $B^0 \to D^{*-}\ell^{+}ν_\ell$ decay in the framework of HQET, based on a sample of about 52,800 $B^0 \to D^{*-}\ell^{+}ν_\ell$ decays recorded by the BABAR detector. The kinematical information of the fully reconstructed decay is used to extract the following values for the parameters (where the first errors are statistical and the second systematic): $ρ^2 = 1.156 \pm 0.094 \pm 0.028$, $R_1 = 1.329 \pm 0.131 \pm 0.044$, $R_2 = 0.859 \pm 0.077 \pm 0.022$, $\mathcal{F}(1)|V_{cb}| = (35.03 \pm 0.39 \pm 1.15) \times 10^{-3}$. By combining these measurements with the previous BABAR measurements of the form factors which employs a different technique on a partial sample of the data, we improve the statistical accuracy of the measurement, obtaining: $ρ^2 = 1.179 \pm 0.048 \pm 0.028, R_1 = 1.417 \pm 0.061 \pm 0.044, R_2 = 0.836 \pm 0.037 \pm 0.022, $ and $ \mathcal{F}(1)|V_{cb}| = (34.68 \pm 0.32 \pm 1.15) \times 10^{-3}.$ Using the lattice calculations for the axial form factor $\mathcal{F}(1)$, we extract $|V_{cb}| =(37.74 \pm 0.35 \pm 1.25 \pm ^{1.23}_{1.44}) \times 10^{-3}$, where the third error is due to the uncertainty in $\mathcal{F}(1)$.

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arXiv2006

Measurement of Decay Amplitudes of \B \to (\ccbar) \Kstar with an angular analysis, for (\ccbar)=\jpsi, \psitwos and \chicone

We perform the first three-dimensional measurement of the amplitudes of $B\toψ{(2S)}K^*$ and $B\toχ_{c1}K^*$ decays and update our previous measurement for $B\to{J\mskip -3mu/\mskip -2muψ\mskip 2mu}K^*$. We use a data sample collected with the {\slshape BABAR} detector at the PEP-II storage ring, representing 232 million produced $B{\kern 0.18em\bar{\kern -0.18em B}}$ pairs. The longitudinal polarization of decays to the $1^{++} χ_{c1}$ meson together with a $K^*$ meson, is found to be larger than that for the decay to the $1^{--} Ψ$ mesons. No direct CP-violating charge asymmetry is observed.

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arXiv2006

A precision measurement of the D_s1(2536) meson mass and decay width

The decay width and the mass of the D_s1(2536) have been measured via the decay channel D_s1 -> D*+K_S using 232 fb^-1 of data collected with the BABAR detector at the PEP-II asymmetric-energy e+e- storage ring. The result for the decay width is (1.03 +- 0.05 +- 0.12) MeV/c^2, with the first error denoting the statistical uncertainty and the second one the systematic uncertainty. For the mass, a value of (2534.85 +- 0.02 +- 0.40) MeV/c^2 has been obtained. The systematic error is dominated by the uncertainty on the D*+ mass. The mass difference between the D_s1 and D*+ has been measured to be (524.85 +- 0.02 +- 0.04) MeV/c^2.

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arXiv2006

Measurement of the Hadronic Form Factors in Ds -> phi e nu Decays

Based on the measured four-dimensional rate for $D_{s}^+ to ϕe^+ ν_e$ decays, we have determined the ratios of the three hadronic form factors, r_V=V(0)/A_1(0)= 1.636 \pm 0.067 \pm 0.038 and r_2=A_2(0)/A_1(0)= 0.705 \pm 0.056 \pm 0.029, using a simple pole ansatz for the $q^2$ dependence, with fixed values of the pole masses for both the vector and axial form factors. By a separate fit to the same data, we have also extracted the pole mass for the axial form factors, $m_A$: r_V=V(0)/A_1(0)= 1.633 \pm 0.081 \pm 0.068 ,r_2=A_2(0)/A_1(0)= 0.711 \pm 0.111 \pm 0.096 and m_A=(2.53^{+0.54}_{-0.35}\pm 0.54){{GeV/}c^2}

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arXiv2006

Xic' Production at BABAR

Using 232 fb-1 of data collected by the BABAR detector, the Xic'+ and Xic'0 baryons are reconstructed through the decays: Xic'+ -> Xic+ gamma and Xic'0 -> Xic0 gamma, where Xic+ -> Xi- pi+ pi+ and Xic0 -> Xi- pi+. By measuring the efficiency-corrected yields in different intervals of the center-of-mass momentum, the production rates from B decays and from the continuum are extracted. For production from B decays, the branching fractions are found to be B(B -> Xic'+ X) x B(Xic+ -> Xi- pi+ pi+) = [ 1.69 +- 0.17 (exp.) +- 0.10 (model) ] x 10^-4 and B(B -> Xic'0 X) x B(Xic0 -> Xi- pi+) = [ 0.67 +- 0.07 (exp.) +- 0.03 (model) ] x 10^-4. For production from the continuum the cross-sections are found to be sigma(e+ e- -> Xic'+ X) x B(Xic+ -> Xi- pi+ pi+) = 141 +- 24 (exp.) +- 19 (model) fb and sigma(e+ e- -> Xic'0 X) x B(Xic0 -> Xi- pi+) = 70 +- 11 (exp.) +- 6 (model) fb. The helicity angle distributions of Xic' decays are studied and found to be consistent with J = 1/2.

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arXiv2006

Study of the Exclusive Initial-State Radiation Production of the $D \bar D$ System

A study of exclusive production of the $D \bar D$ system through initial-state r adiation is performed in a search for charmonium states, where $D=D^0$ or $D^+$. The $D^0$ mesons are reconstructed in the $D^0 \to K^- π^+$, $D^0 \to K^- π^+ π^0$, and $D^0 \to K^- π^+ π^+ π^-$ decay modes. The $D^+$ is reconstructed through the $D^+ \to K^- π^+ π^+$ decay mode. The analysis makes use of an integrated luminosity of 288.5 fb$^{-1}$ collected by the BaBar experiment. The $D \bar D$ mass spectrum shows a clear $ψ(3770)$ signal. Further structures appear in the 3.9 and 4.1 GeV/$c^2$ regions. No evidence is found for Y(4260) decays to $D \bar D$, implying an up per limit $\frac{\BR(Y(4260)\to D \bar D)}{\BR(Y(4260)\to J/ψπ^+ π^-)} < 7.6$ (95 % confidence level).

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arXiv2006

Observation of the decays B- to Ds(*)+ K- pi-

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.

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arXiv2006

Search for b--> u transitions in B- -> [K+pi-pi0]_D K-

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.

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arXiv2006

Measurement of the B+ --> eta l+ nu and B+ --> eta' l+ nu Branching Fractions using Upsilon(4S)-->BBbar Events Tagged by a Fully Reconstructed B Meson

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.

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arXiv2006

Measurement of the Relative Branching Fractions for B- -> D/D*/D**(D(*)pi) l- anti-nu with a Large Sample of Tagged B Mesons

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.) .

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arXiv2006

Search for Flavor-Changing Neutral-Current Charm Decays

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.

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arXiv2006

Search for inclusive charmless B->K+X and B->K0X decays

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.).

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arXiv2006

Measurement of the Branching Fractions of the Decays $\bar{B}^{0} \to Λ_{c}^{+} \bar{p}$ and $B^{-} \to Λ_{c}^{+} \bar{p} π^{-}$

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.

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arXiv2006

Measurement of the B0->pilnu Form Factor Shape and Branching Fraction, and Determination of |Vub| with a Loose Neutrino Reconstruction Technique

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.

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arXiv2006

Search for B+ --> X(3872) K+, X(3872) --> J/psi gamma

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.

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arXiv2006

Measurements of branching fractions, polarizations, and direct CP-violation asymmetries in B --> rho K* and B --> f0(980) K* decays

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.

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arXiv2006

Search for the Baryon and Lepton Number Violating Decays tau -> Lambda h

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.

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