arXiv subjects

The BABAR Collaboration

Publications and source records attributed to The BABAR Collaboration.

At least 415 records · Page 23Linked to original sources

arXiv2006

The e+ e- --> 3(pi+pi-), 2(pi+pi-pi0) and K+K- 2(pi+pi-) Cross Sections at Center-of-Mass Energies from Production Threshold to 4.5 GeV Measured with Initial-State Radiation

We study the processes e+ e- --> 3(pi+pi-)gamma, 2(pi+pi-pi0)gamma and K+ K- 2(pi+pi-)gamma, with the photon radiated from the initial state. About 20,000, 33,000 and 4,000 fully reconstructed events, respectively, have been selected from 232 fb-1 of BaBar data. The invariant mass of the hadronic final state defines the effective e+e- center-of-mass energy, so that these data can be compared with the corresponding direct e+e- measurements. From the 3(pi+pi-), 2(pi+pi-pi0) and K+ K- 2(pi+pi-) mass spectra, the cross sections for the processes e+ e- --> 3(pi+pi-), e+ e- --> 2(pi+pi-pi0) and e+ e- --> K+ K- 2(pi+pi-) are measured for center-of-mass energies from production threshold to 4.5 GeV. The uncertainty in the cross section measurement is typically 6-15%. We observe the J/psi in all these final states and measure the corresponding branching fractions.

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arXiv2006

Measurement of Branching Fractions and Resonance Contributions for B0 -> D0bar K+ pi- and Search for B0 -> D0 K+ pi- Decays

Using 226 million $Υ(4S)\to B\bar{B}$ events collected with the BaBar detector at the PEP-II $e^+e^-$ storage ring at the Stanford Linear Accelerator Center, we measure the branching fraction for $B^0\to \bar{D}^0 K^+π^-$, excluding $B^0\to D^{*-} K^+$ to be $ {\cal B}(B^0\to \bar{D}^0 K^+π^-) = (88 \pm 15 \pm 9)\times 10^{-6} . $ We observe $B^0\to \bar{D}^0 K^*(892)^0$ and $B^0\to D_2^*(2460)^- K^+$ contributions. The ratio of branching fractions ${\cal B}(B^0\to D^{*-}K^+)/{\cal B}(B^0\to D^{*-}π^+) = (7.76\pm 0.34 \pm 0.29)%$ is measured separately. The branching fraction for the suppressed mode $B^0\to D^0 K^+π^-$ is $ {\cal B}(B^0\to D^0 K^+π^-) < 19 \times 10^{-6} $ at the 90% confidence level.

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arXiv2005

Measurements of the branching fractions and CP-asymmetries of B- --> D0_(CP) K- decays

We present a study of the decay B- --> D0_(CP) K- and its charge conjugate, where D0_(CP) is reconstructed in CP-even, CP-odd, and non-CP flavor eigenstates, based on a sample of 232 million Y(4S) --> B Bbar decays collected with the BABAR detector at the PEP-II e+e- storage ring. We measure the partial-rate charge asymmetries A_CP+, A_CP- and the ratios R_CP+, R_CP- of the B --> D0 K decay branching fractions as measured in CP+, CP-, and non-CP D0 decays: A_CP+ = 0.35 +/- 0.13 (stat) +/- 0.04 (syst) A_CP- = -0.06 +/- 0.13 (stat) +/- 0.04 (syst) R_CP+ = 0.90 +/- 0.12 (stat) +/- 0.04 (syst) R_CP- = 0.86 +/- 0.10 (stat) +/- 0.05 (syst)

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arXiv2005

Search for rare quark-annihilation decays, B --> Ds(*) Phi

We report on searches for B- --> Ds- Phi and B- --> Ds*- Phi. In the context of the Standard Model, these decays are expected to be highly suppressed since they proceed through annihilation of the b and u-bar quarks in the B- meson. Our results are based on 234 million Upsilon(4S) --> B Bbar decays collected with the BABAR detector at SLAC. We find no evidence for these decays, and we set Bayesian 90% confidence level upper limits on the branching fractions BF(B- --> Ds- Phi) < 1.9x10^(-6) and BF(B- --> Ds*- Phi)<1.2x10^(-5). These results are consistent with Standard Model expectations.

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arXiv2005

Search for the Rare Decays B0 -> Ds(*)+ a0(2)-

We have searched for the decays $B^0 \rightarrow D_s^{+}a_0^-$, $B^0 \rightarrow D_s^{*+}a_0^-$, $B^0 \rightarrow D_s^{+}a_2^-$ and $B^0 \rightarrow D_s^{*+}a_2^-$ in a sample of about 230 million $Υ(4S) \rightarrow B{\bar B}$ decays collected with the {\sl BaBar} detector at the PEP-II asymmetric-energy $B$-factory at SLAC. We find no evidence for these decays and set upper limits at 90\% C.L. on the branching fractions: ${\cal B}(B^0 \rightarrow D_s^+ a_0^-) < 1.9\times 10^{-5}$, ${\cal B}(B^0 \rightarrow D_s^{*+} a_0^-) < 3.6\times 10^{-5}$, ${\cal B}(B^0 \rightarrow D_s^+ a_2^-) < 1.9 \times 10^{-4}$, and ${\cal B}(B^0 \rightarrow D_s^{*+} a_2^-) < 2.0\times 10^{-4} $.

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arXiv2005

A study of e+e- -> p anti-p using initial state radiation with BABAR

The e+e- -> p anti-p cross section is determined over a range of p anti-p masses, from threshold to 4.5 GeV/c^2, by studying the e+e- -> p anti-p gamma process. The data set corresponds to an integrated luminosity of 232 fb^-1, collected with the BABAR detector at the PEP-II storage ring, at an e+e- center-of-mass energy of 10.6 GeV. The mass dependence of the ratio of electric and magnetic form factors, |G_E/G_M|, is measured for p anti-p masses below 3 GeV/c^2; its value is found to be significantly larger than 1 for masses up to 2.2 GeV/c^2. We also measure J/psi -> p anti-p and psi(2S) -> p anti-p branching fractions and set an upper limit on Y(4260) -> p anti-p production and decay.

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arXiv2005

Study of B --> pi l nu and B --> rho l nu decays and determination of |Vub|

We present an analysis of exclusive charmless semileptonic B-meson decays based on 83 million BBbar pairs recorded with the BABAR detector at the Upsilon(4S) resonance. Using isospin symmetry, we measure branching fractions B(B0 --> pi- l+ nu) = (1.38 +- 0.10 +- 0.16 +- 0.08) x 10^-4 and B(B0 --> rho- l+ nu) = (2.14 +- 0.21 +- 0.48 +- 0.28) x 10^-4, where the errors are statistical, experimental systematic, and due to form-factor shape uncertainties. We compare the measured distribution in q^2, the momentum-transfer squared, with theoretical predictions for the form factors from lattice QCD and light-cone sum rules, and extract the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |V_{ub}| = (3.82 +- 0.14 +- 0.22 +- 0.11 +0.88 -0.52) x 10^-3 from B --> pi l nu, where the fourth error reflects the uncertainty of the form-factor normalization.

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arXiv2005

Measurement of the Branching Ratios Gamma(D_s+ -> D_s+ pi0)/Gamma(D_s+ -> D_s+ gamma) and Gamma(D0+ -> D0 pi0)/Gamma(D0* -> D0 gamma)

Data samples corresponding to the isospin-violating decay $D_s^{*+}\to D_s^+ π^0$ and the decays $D_s^{*+}\to D_s^+γ$, $D^{*0}\to D^0π^0$ and $D^{*0}\to D^0γ$ are reconstructed using 90.4 ${\rm fb}^{-1}$ of data recorded by the BaBar detector at the PEP-II asymmetric-energy $e^+e^-$ collider. The following branching ratios are extracted: $Γ(D_s^{*+}\to D_s^+ π^0)/Γ(D_s^{*+}\to D_s^+γ) = 0.062\pm0.005 ({\rm stat.})\pm0.006 ({\rm syst.})$ and $Γ(D^{*0}\to D^0π^0)/Γ(D^{*0}\to D^0γ) = 1.74\pm0.02 ({\rm stat.})\pm0.13 ({\rm syst.})$. Both measurements represent significant improvements over present world averages.

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arXiv2005

Search for the W-exchange decays B0 --> Ds()- Ds()+

We report a search for the decays $B^{0} \to D_{s}^{-} D_{s}^{+}$, $B^{0} \to D_{s}^{*-} D_{s}^{+}$, $B^{0} \to D_{s}^{*-} D_{s}^{*+}$ in a sample of 232 million $Υ(4S)$ decays to \BBb ~pairs collected with the \babar detector at the PEP-II asymmetric-energy $e^+ e^-$ storage ring. We find no significant signal and set upper bounds for the branching fractions: ${\cal B}(B^{0} \to D_{s}^{-} D_{s}^{+}) < 1.0 \times 10^{-4}, {\cal B}(B^{0} \to D_{s}^{*-} D_{s}^{+}) < 1.3 \times 10^{-4}$ and ${\cal B}(B^{0} \to D_{s}^{*-} D_{s}^{*+}) < 2.4 \times 10^{-4}$ at 90% confidence level.

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arXiv2005

Search for B -> J/psi D Decays

We report a search for B -> J/psi D decays, based on a sample of 124 10^6 BBbar events collected with the BABAR detector at the PEP-II storage ring of the Stanford Linear Accelerator Center. No significant signal is found. We obtain upper limits on the branching fractions of 1.3 10^{-5} for B0 -> J/psi D0bar and 1.2 10^{-4} for B+ -> J/psi D+ at 90% confidence level.

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arXiv2005

Measurements of the B -> X_s gamma Branching Fraction and Photon Spectrum from a Sum of Exclusive Final States

Using 88.9 million BB events collected by the BaBar detector at the Y(4S), we measure the branching fraction for the radiative penguin process B -> X_s gamma from the sum of 38 exclusive final states. The inclusive branching fraction above a minimum photon energy E_gamma > 1.9 GeV is BF (b -> s gamma) = (3.27 +/- 0.18 (stat.) +0.55/-0.40 (syst.) +0.04/-0.09 (theory)) 10^-4. We also measure the isospin asymmetry between B^- -> X_s ubar gamma and B^0bar -> X_s dbar gamma to be Delta_0- = -0.006 +/- 0.058 (stat.) +/- 0.009 (syst.) +/- 0.024 (B^0bar / B^-). The photon energy spectrum is measured in the B rest frame, from which moments are derived for different values of the minimum photon energy. We present fits to the photon spectrum and moments which give the heavy-quark parameters m_b and mu_pi^2. The fitted parameters are consistent with those obtained from semileptonic B -> X_c l nu decays, and are useful inputs for the extraction of Vub from measurements of semileptonic B -> X_u l nu decays.

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arXiv2005

Observation of a Broad Structure in the $π^+π^-J/ψ$ Mass Spectrum around 4.26 GeV/$c^2$

We study initial-state radiation events, $e^+e^- \to γ_{ISR}π^+π^-J/ψ$, with data collected with the BaBar detector. We observe an accumulation of events near 4.26 GeV/$c^2$ in the invariant-mass spectrum of $π^+π^-J/ψ$. Fits of the mass spectrum indicate that a broad resonance with a mass of about 4.26 GeV/$c^2$ is required to describe the observed structure. The presence of additional narrow resonances cannot be excluded. The fitted width of the broad resonance is 50 to 90 MeV/$c^2$, depending on the fit hypothesis.

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arXiv2005

Improved Measurements of Branching Fractions for B0 -> pi+pi-, K+pi-, and Search for K+K- at BaBar

We present preliminary measurements of branching fractions for the charmless two-body decays B0 -> pi+pi- and K+pi-, and a search for B0 -> K+K- using a data sample of approximately 227 million BBbar decays. Signal yields are extracted with a multi-dimensional maximum likelihood fit, and the efficiency is corrected for the effects of final-state radiation. We find the charge-averaged branching fractions (in units of 10^{-6}): Br(B0 -> pi+pi-) = 5.5 +- 0.4 +- 0.3, Br(B0 -> K+pi-) = 19.2 +- 0.6 +- 0.6, Br(B0 -> K+K-) = < 0.40. The errors are statistical followed by systematic, and the upper limit on K+K- represents a confidence level of 90%.

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arXiv2005

Search for b->u transitions in B- -> D0 K- and B- -> D*0 K-

We search for B- ==> \tilde{D0}K- and B- ==> \tilde{D*0}K-, with \tilde{D*0} ==> \tilde{D0}pi0 or \tilde{D*0} ==> \tilde{D0}gamma, and \tilde{D0} ==> K+pi- (and charge conjugates). These final states can be reached through the b==>c transition B- ==> D0(*)K- followed by the doubly CKM-suppressed D0 ==> K+pi-, or the b==>u transition B- ==> D0bar(*)K- followed by the CKM-favored D0bar ==> K+pi-. The interference of these two amplitudes is sensitive to the angle gamma of the unitarity triangle. Our results are based on 232 million Upsilon(4S)==>BBbar decays collected with the BaBar detector at SLAC. We find no significant evidence for these decays. We set a limit r_B = |A(B- ==> D0bar K-)/A(B- ==> D0 K-)| < 0.23 at 90% C.L. using the most conservative assumptions on the values of the CKM angle gamma and the strong phases in the B and D decay amplitudes. In the case of the D* we set a 90% C.L. limit r*_B^2 = |A(B- ==> D*0bar K-)/A(B- ==> D*0 K-)|^2 < (0.16)^2 which is independent of assumptions on gamma and strong phases.

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arXiv2005

Measurement of the B0 --> pi- l+ nu and B+ --> pi0 l+ nu Branching Fractions and Determination of |V_ub| in Y(4S) Events Tagged by a Fully Reconstructed B Meson

We report preliminary measurements of the charmless exclusive semileptonic branching fractions of the B0 --> pi- l+ nu and B+ --> pi0 l+ nu decays, based on 211 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 second B meson is identified by the detection of a charged lepton and a pion. We measure the partial branching fractions for B0 --> pi- l+ nu and B+ --> pi0 l+ nu in three regions of the invariant mass squared of the lepton pair, and we obtain the total branching fractions BF(B0 --> pi- l+ nu) = (1.14 +/- 0.27(stat) +/- 0.17(syst)) x 10^-4 and BF(B+ --> pi0 l+ nu) = (0.86 +/- 0.22(stat) +/- 0.11(syst)) x 10^-4. Using isospin symmetry, we measure the combined total branching fraction BF(B0 --> pi- l+ nu) = (1.28 +/- 0.23(stat) +/- 0.16(syst)) x 10^-4. Theoretical predictions of the form-factor are used to determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element |V_ub| = (3.7 +/- 0.3(stat) +/- 0.2(syst) +0.8-0.5(FF)) x 10^-3, where the last error is due to the form-factor normalization.

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arXiv2005

Measurement of Double Charmonium Production in $e^+e^-$ Annihilations at $\sqrt{s}=10.6$ GeV

We study $e^+e^-\to J/ψc\bar{c}$ by measuring the invariant mass distribution recoiling against fully reconstructed $J/ψ$ decays, using 124 fb$^{-1}$ of data collected with a center-of-mass energy of 10.6 GeV with the $BaBar$ detector. We observe signals for $η_c(1S)$, $χ_{c0}$, and $η_c(2S)$ in the recoil mass distribution, thus confirming previous measurements. We measure $σ(e^+e^-\to J/ψ+c\bar{c}) {\cal B} (c\bar{c} \to >2 \mathrm{charged})$ to be $17.6\pm2.8\textrm{(stat)}^{+1.5}_{-2.1}\textrm{(syst)}$ fb, $10.3\pm2.5\textrm{(stat)}^{+1.4}_{-1.8}\textrm{(syst)}$ fb, and $16.4\pm3.7\textrm{(stat)}^{+2.4}_{-3.0}\textrm{(syst)}$ fb with $c\bar{c}=η_c(1S)$, $χ_{c0}$, and $η_c(2S)$, respectively.

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arXiv2005

Measurement of the Branching Fraction of Upsilon(4S) --> B0B0bar

We report the first measurement of the branching fraction f00 for Upsilon(4S) --> B0B0bar. The data sample consists of 81.7 fb^-1 collected at the Upsilon(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy e^+e^- storage ring. Using partial reconstruction of the decay B0bar --> D^{*+} \ell^{-} \barν_{\ell} in which only the charged lepton and the soft pion from the decay D^{*+} --> D0 pi^+ are reconstructed, we obtain f00 = 0.487 \pm 0.010(stat) \pm 0.008(sys). Our result does not depend on the branching fractions of B0bar --> D^{*+} \ell^{-} \barν_{\ell} and D^{*+} --> D0 pi^+ decays, on the ratio of the charged and neutral B meson lifetimes, nor on the assumption of isospin symmetry.

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arXiv2005

Measurement of the time-dependent CP-violating asymmetry in $B^0 \to K^{0}_sπ^0γ$ decays

We present a measurement of the time-dependent CP-violating asymmetry in $B^0 \to K^{*}_0γ$ decays with $K^{*}_0\to K^{0}_sπ^0$ based on 232 million $Υ(4\mathrm{S})\to B\bar{B}$ decays collected with the BaBar detector at the PEP-II asymmetric-energy $e^{+}e^{-}$ collider at SLAC. In a sample containing $157\pm 16$ signal decays, we measure $S_{K^{*}_0γ} = -0.21 \pm 0.40 \pm 0.05$ and $C_{K^{*}_0γ}= -0.40 \pm 0.23 \pm 0.03$, where the first error is statistical and the second systematic. We also explore $B^0 \to K^{0}_sπ^0γ$ decays with $1.1<m_{K^{0}_sπ^0}<1.8$ GeV$/c^2$ and find $59\pm13$ signal events with $S_{K^{0}_sπ^0} = 0.9 \pm 1.0 \pm 0.2$ and $C_{K^{0}_sπ^0} = -1.0 \pm 0.5 \pm 0.2$.

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