arXiv subjects

The BABAR Collaboration

Publications and source records attributed to The BABAR Collaboration.

At least 379 records · Page 21Linked to original sources

arXiv2006

Study of the Lepton Flavor Violating Decay $τ^{-} \to μ^{-} η$

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 $τ^- \to μ^-η$.

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arXiv2006

Search for the rare decay B to pi l+ l-

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.

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arXiv2006

Measurement of the Mass and Width and Study of the Spin of the Xi(1690)0 Resonance from Lambdac+ --> Lambda anti-K0 K+ Decay at Babar

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.

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arXiv2006

A Study of Xi_c(2980)^+ and Xi_c(3077)^+

We present a study of two states decaying to Lambda_c^+K^-pi^+ using the BaBar detector at the SLAC PEP-II asymmetric-energy e^+e^- storage rings. We use an integrated luminosity of 288.5 fb^{-1} collected at the center-of-mass energy sqrt{s} = 10.58 GeV, near the peak of the Upsilon(4S) resonance, plus 27.2 fb^{-1} collected approximately 40 MeV below this energy. We search for the particles Xi_{c}(2980)^+ and Xi_{c}(3077)^+, recently discovered by the Belle Collaboration, in their decays to Lambda_c^+K^-pi^+, where Lambda_c^+rightarrow pK^-pi^+. We find a signal with 7.0 sigma significance for the Xi_c(2980)^+ state with a mass difference with respect to the Lambda_c^+ of (680.6pm1.9pm1.0) MeV/c^2 (first error is statistical and second error is systematic). The measured width for this state is (23.6pm2.8pm1.3) MeV, and the yield is 284pm45pm46 events. We find a signal with 8.6 sigma significance for the Xi_c(3077)^+ state with a mass difference with respect to the Lambda_c^+ of (790.0pm0.7pm0.2) MeV/c^2, a width of (6.2pm1.6pm0.5) MeV, and a yield of 204pm35pm12 events. The Xi_{c}(2980)^+ is found to decay resonantly through the intermediate state Sigma_c(2455)^{++}K^- with 4.9 sigma significance and non-resonantly to Lambda_c^+K^-pi^+ with 4.1 sigma significance. With 5.8 sigma significance, the Xi_c(3077)^+ is found to decay resonantly through Sigma_c(2455)^{++}K^-, and with 4.6 sigma significance, it is found to decay through Sigma_c(2520)^{++}K^-. The significance of the signal for the non-resonant decay Xi_c(3077)^+rightarrow Lambda_c^+K^-pi^+ is 1.4 sigma. These results are preliminary.

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arXiv2006

Measurement of the D+ --> pi+ pi0 and D+ --> K+ pi0 Branching Fractions

We present measurements of the branching fractions for the Cabbibo suppressed decays D+ --> pi+ pi0 and D+ --> K+ pi0 based on a data sample corresponding to an integrated luminosity of 124.3 fb-1. The data were taken with the BABAR detector at the PEP-II B Factory operating on and near the Y(4S) resonance. We find BR(D+ --> pi+ pi0) = (1.22 +/- 0.10 +/- 0.08 +/- 0.08) * 10^(-3) and BR(D+ --> K+ pi0) = (2.46 +/- 0.46 +/- 0.24 +/- 0.16) * 10^(-4), where the first uncertainty is statistical, the second systematic and the last error is due to the uncertainties in the absolute branching fraction scale for D+ mesons. This represents the first observation of the doubly Cabibbo-suppressed D+ --> K+ pi0 decay mode and an improved measurement of the D+ --> K+ pi0 branching fraction.

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arXiv2006

Measurements of the Decays $B^0 \to \bar{D}^0\proton\antiproton$, $B^0 \to \bar{D}^{0}\proton\antiproton$, $B^0 \to D^{-}\proton\antiprotonπ^+$, and $B^0 \to D^{-}\proton\antiprotonπ^+$

We present measurements of branching fractions of $B^0$ decays to multi-body final states containing protons, based on 232 million $Υ(4S)\to B\bar{B}$ decays collected with the BaBar detector at the SLAC PEP-II asymmetric-energy $B$ factory. We measure the branching fractions ${\cal B}(B^0 \to \bar{D}^0\proton\antiproton)=(1.13\pm0.06\pm0.08)\times 10^{-4}$, ${\cal B}(B^0 \to \bar{D}^{*0}\proton\antiproton)=(1.01\pm0.10\pm0.09)\times 10^{-4}$, ${\cal B}(B^0 \to D^{-}\proton\antiprotonπ^+)=(3.38\pm0.14\pm0.29)\times 10^{-4}$, and ${\cal B}(B^0 \to D^{*-}\proton\antiprotonπ^+)=(4.81\pm0.22\pm0.44)\times 10^{-4}$ where the first error is statistical and the second systematic. We present a search for the charmed pentaquark state, $Θ_c(3100)$ observed by H1 and put limits on the branching fraction ${\cal B} (B^0 \to Θ_c \antiprotonπ^+)\times{\cal B}(Θ_c \to D^{*-}\proton)<14\times10^{-6}$ and ${\cal B}(B^0 \to Θ_c \antiprotonπ^+)\times{\cal B}(Θ_c\to D^-\proton)<9\times10^{-6}$. Upon investigation of the decay structure of the above four $B^{0}$ decay modes, we see an enhancement at low $p\bar{p}$ mass and deviations from phase-space in the $\bar{D}\bar{p}$ and $\bar{D}p$ invariant mass spectra.

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arXiv2006

Measurement of B Decays to phi K gamma

We measure the branching fraction of the radiative B- decay B(B- -> phi K- gamma) = (3.46 +/- 0.57^{+0.39}_{-0.37}) 10^-6, and set an upper limit on the radiative B0 decay B(B0 -> phi K0 gamma) < 2.71 10^-6 at 90% confidence level. We also measure the direct CP asymmetry of the B- -> phi K- gamma mode A_CP = (-26.4 +/- 14.3 +/- 4.8)%. The uncertainties are statistical and systematic, respectively. These measurements are based on 207 1/fb of data collected at the Y4S resonance with the BABAR detector.

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arXiv2006

Search for Doubly Charmed Baryons Xi_cc^+ and Xi_cc^++ in BABAR

We search for the production of doubly charmed baryons in e^+e^- annihilations at or near a center-of-mass energy of 10.58 GeV, in a data sample with an integrated luminosity of 232 fb^-1 recorded with the BABAR detector at the PEP-II storage ring at the Stanford Linear Accelerator Center. We search for Xi_cc^+ baryons in the final states Lambda_c^+K^-pi^+ and Xi_c^0pi^+, and Xi_cc^++ baryons in the final states Lambda_c^+K^-pi^+pi^+ and Xi_c^0pi^+pi^+. We find no evidence for the production of doubly charmed baryons.

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arXiv2006

Search for B+ -> phi pi+ and B0 -> phi pi0 Decays

A search has been made for the decays B+ -> phi pi+ and B0->to phi pi0 in a data sample of approximately 232 x 10^6 B Bbar pairs recorded at the Upsilon(4S) resonance with the BaBar detector at the PEP-II B-meson Factory at SLAC. No significant signals have been observed, and therefore upper limits have been set on the branching fractions: BR(B+ ->phi pi+)<2.4 x 10^{-7} and BR(B0->phi pi0)<2.8 x 10^{-7} at 90% probability.

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arXiv2006

Observation of $e^+e^-$ Annihilations into the $\boldmath{C=+1}$ Hadronic Final States $ρ^0ρ^0$ and $ϕρ^0$

We report the first observation of $e^+e^-$ annihilations into states of positive $C$-parity, namely $ρ^0 ρ^0$ and $ϕρ^0$. The two states are observed in the $\pip\pim\pip\pim$ and $K^+K^-\pip\pim$ final states, respectively, in a data sample of 225~$fb^{-1}$ collected by the $BaBar$~experiment at the $PEP-II$ $e^+e^-$ storage rings at energies near $\sqrt{s} ~=$ 10.58~$GeV$. The distributions of $\cosθ^*$, where $θ^*$ is the center-of-mass polar angle of the $ϕ$ meson or the forward $ρ^0$ meson, suggest production by two-virtual-photon annihilation. We measure cross sections within the range $|\cosθ^*| ~<~ 0.8$ of $σ(\e^+e^- \to ρ^0 ρ^0) ~=~$$20.7 \pm 0.7 (\mathrm{stat})\pm 2.7(\mathrm{syst}) ~\mathrm{fb}$ and $σ(\e^+e^- \to ϕρ^0) \~=~$$5.7\pm 0.5(\mathrm{stat}) \pm 0.8(\mathrm{syst}) ~\mathrm{fb}$.

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arXiv2006

Search for the decay of a B0 or B0bar meson to K0bar K0 or K0 K0bar

We present a search for the decay of a B0 or B0bar meson to a K*0bar K0 or K*0 K0bar final state, using a sample of approximately 232 million BBbar events collected with the BABAR detector at the PEP-II asymmetric energy e+e- collider at SLAC. The measured branching fraction is B(B0 --> K*0bar K0) + B(B0 --> K*0 K0bar) = (0.2+0.9-0.8+0.1-0.3)x 10-6. We obtain the following upper limit for the branching fraction at 90% confidence level: B(B0 --> K*0bar K0) + B(B0 --> K*0 K0bar) <1.9 x 10-6. We use our result to constrain the Standard Model prediction for the deviation of the CP asymmetry in B0 --> phi K0 from sin(2beta).

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arXiv2006

Measurement of the Spin of the Omega^- Hyperon at BABAR

A measurement of the spin of the Omega^- hyperon produced through the exclusive process Xi_c^0 --> Omega^- K^+ is presented using a total integrated luminosity of 116 fb^-1 recorded with the BABAR detector at the e^+ e^- asymmetric-energy B-Factory at SLAC. Under the assumption that the Xi_c^0 has spin 1/2, the angular distribution of the Lambda from Omega^- --> Lambda K^- decay is inconsistent with all half-integer Omega^- spin values other than 3/2. Lower statistics data for the process Omega_c^0 --> Omega^- pi^+ from a 230 fb^-1 sample are also found to be consistent with Omega^- spin 3/2. If the Xi_c^0 spin were 3/2, an Omega^- spin of 5/2 cannot be excluded.

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arXiv2006

Study of Inclusive B- and Bbar0 Decays to Flavor-Tagged D, D_s and Lambda_c

We report on a study of inclusive $B^-$ and $\bar{B}^0$ meson decays to ${D^0 X}$, ${\bar{D}^0 X}$, ${D^+ X}$, ${D^- X}$, ${D_s^+ X}$, ${D_s^- X}$, ${Λ_c^+ X}$, ${\barΛ_c^- X}$, based on a sample of 231 million $B\bar{B}$ events recorded with the BABAR detector at the $Υ{(4S)}$ resonance. Events are selected by completely reconstructing one $B$ and searching for a reconstructed charm particle in the rest of the event. From the measured branching fractions of these decays, we infer the number of charm and anti-charm particles per $\bar{B}$ decay, separately for charged and neutral parents. We derive the total charm yield per $B^-$ decay, $n_c^- = 1.202 \pm 0.023\pm 0.040^{+0.035}_{-0.029} $, and per $\bar{B}^0$ decay, $n_c^0 = 1.193 \pm 0.030\pm 0.034^{+0.044}_{-0.035}$ where the first uncertainty is statistical, the second is systematic, and the third reflects the charm branching-fraction uncertainties. We also present the charm momentum distributions measured in the $\bar{B}$ rest frame.

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arXiv2006

A Search for the rare decay B0 --> tau+tau- at BABAR

We present the results of a search for the decay B0 --> tau+tau- in a data sample of (232 +- 3) x 10^6 Upsilon(4S) --> BBbar decays using the BABAR detector. Certain extensions of the Standard Model predict measurable levels of this otherwise rare decay. We reconstruct fully one neutral B meson and seek evidence for the signal decay in the rest of the event. We find no evidence for signal events and obtain B(B0 --> tau+tau-) < 4.1 x 10^-3 at the 90% confidence level.

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arXiv2006

Determinations of |Vub| from Inclusive Semileptonic B Decays with Reduced Model Dependence

We report two novel determinations of |Vub| with reduced model dependence, based on measurements of the mass distribution of the hadronic system in semileptonic B decays. 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 from Y(4S) to BBbar events. In one approach, we combine the inclusive B to X_u l nu rate, integrated up to a maximum hadronic mass m_X < 1.67GeV, with a measurement of the inclusive B to X_s gamma photon energy spectrum. We obtain |Vub| = (4.43 +- 0.38stat +- 0.25syst +- 0.29theo)*10^-3. In another approach we measure the total B to X_u l nu rate over the full phase space and find |Vub| = (3.84 +- 0.70stat +- 0.30syst +- 0.10theo)*10^-3.

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arXiv2006

Search for the Charmed Pentaquark Candidate Theta_c(3100) in e+e- Annihilations at sqrt(s)=10.58 GeV

We search for the charmed pentaquark candidate reported by the H1 collaboration, the Theta_c(3100)^0, in e^+e^- interactions at a center-of-mass (c.m.) energy of 10.58 GeV, using 124~fb-1 of data recorded with the BaBar detector at the PEP-II e^+e^- facility at SLAC. We find no evidence for such a state in the same pD^{*-} decay mode reported by H1, and we set limits on its production cross section times branching fraction into pD^{*-} as a function of c.m. momentum. The corresponding limit on its total rate per e^+e^- -> qqbar event, times branching fraction, is about three orders of magnitude lower than rates measured for the charmed Lambda_c and Sigma_c baryons in such events.

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arXiv2006

Measurement of Branching Fractions and CP-Violating Charge Asymmetries for B Meson Decays to D()D(), and Implications for the CKM Angle gamma

We present measurements of the branching fractions and charge asymmetries of B decays to all D(*)D(*) modes. Using 232 million BBbar pairs recorded on the Upsilon(4S) resonance by the BaBar detector at the e+e- asymmetric B factory PEP-II at the Stanford Linear Accelerator Center, we measure the branching fractions BF(B0 -> D*+D*-) = (8.1 +- 0.6 +- 1.0) x 10^-4, BF(B0 -> D*+-D-+) = (5.7 +- 0.7 +- 0.7) x 10^-4, BF(B0 -> D+D-) = (2.8 +- 0.4 +- 0.5) x 10^-4, BF(B+ -> D*+D*0) = (8.1 +- 1.2 +- 1.2) x 10^-4, BF(B+ -> D*+D0) = (3.6 +- 0.5 +- 0.4) x 10^-4, BF(B+ -> D+D*0) = (6.3 +- 1.4 +- 1.0) x 10^-4, and BF(B+ -> D+D0) = (3.8 +- 0.6 +- 0.5) x 10^-4, where in each case the first uncertainty is statistical and the second systematic. We also determine the limits BF(B0 -> D*0D*0) < 0.9 x 10^-4, BF(B0 -> D*0D0) < 2.9 x 10^-4, and BF(B0 -> D0D0) < 0.6 x 10^-4, each at 90% confidence level. All decays above denote either member of a charge conjugate pair. We also determine the CP-violating charge asymmetries A(B0 -> D*+-D-+) = 0.03 +- 0.10 +- 0.02, A(B+ -> D*+D*0) = -0.15 +- 0.11 +- 0.02, A(B+ -> D*+D0) = -0.06 +- 0.13 +- 0.02, A(B+ -> D*+D*0) = 0.13 +- 0.18 +- 0.04, and A(B+ -> D+D0) = -0.13 +- 0.14 +- 0.02. Additionally, when we combine these results with information from time-dependent CP asymmetries in B0 -> D*+D*- decays and world-averaged branching fractions of B decays to Ds(*)D(*) modes, we find the CKM phase gamma is favored to lie in the range [0.07-2.77] radians (with a +0 or +pi radians ambiguity) at 68% confidence level.

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arXiv2006

Measurements of branching fractions, rate asymmetries, and angular distributions in the rare decays B --> Kl+l- and B --> K*l+l-

We present measurements of the flavor-changing neutral current decays B --> Kl+l- and B --> K*l+l-, where l+l- is either an e+e- or mu+mu- pair. The data sample comprises 229 x 10^6 Y(4s) -->to BBbar decays collected with the BaBar detector at the PEP-II e+e- storage ring. Flavor-changing neutral current decays are highly suppressed in the Standard Model and their predicted properties could be significantly modified by new physics at the electroweak scale. We measure the branching fractions B(B --> Kll) = (0.34 +- 0.07 +- 0.02) x 10^{-6}, B(B --> K*ll) = (0.78^{+0.19}_{-0.17} +- 0.11) x 10^{-6}, the direct CP asymmetries of these decays, and the relative abundances of decays to electrons and muons. For two regions in l+l- mass, above and below m(Jpsi), we measure partial branching fractions and the forward-backward angular asymmetry of the lepton pair. In these same regions we also measure the K* longitudinal polarization in B --> K*l+l- decays. Upper limits are obtained for the lepton flavor-violating decays B --> Kemu and B --> K*emu. All measurements are consistent with Standard Model expectations.

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