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CLEO Collaboration

Publications and source records attributed to CLEO Collaboration.

At least 235 records · Page 13Linked to original sources

arXiv1999

Hadronic Structure in the Decay $τ^{-}\to π^{-}π^{0}ν_τ$

We report on a study of the invariant mass spectrum of the hadronic system in the decay tau- -> pi- pi0 nu_tau. This study was performed with data obtained with the CLEO II detector operating at the CESR e+ e- collider. We present fits to phenomenological models in which resonance parameters associated with the rho(770) and rho(1450) mesons are determined. The pi- pi0 spectral function inferred from the invariant mass spectrum is compared with data on e+ e- -> pi+ pi- as a test of the Conserved Vector Current theorem. We also discuss the implications of our data with regard to estimates of the hadronic contribution to the muon anomalous magnetic moment.

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arXiv1999

Observation of Radiative Leptonic Decay of the Tau Lepton

Using 4.68 fb^{-1} of e^+e^- annihilation data collected with the CLEO II detector at the Cornell Electron Storage Ring (CESR) we have studied tau radiative decays tau -> mu nu nu gamma and tau -> e nu nu gamma. For a 10 MeV minimum photon energy in the tau rest frame, the branching fraction of radiative tau decay to a muon or electron is measured to be (3.61+-0.16+-0.35)*10^{-3} or (1.75+-0.06+-0.17)*10^{-2}, respectively. The branching fractions are in agreement with the Standard Model theoretical predictions.

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arXiv1999

$b\to sγ$ Branching Fraction and CP Asymmetry

We present preliminary results on $b \to s γ$ from the CLEO experiment. An updated result on the branching fraction is reported at $\cal{B}$$(b \to s γ) = (3.15 \pm 0.35 \pm 0.32 \pm 0.26)\times 10^{-4}$, where the first uncertainty is statistical, the second is systematic, and the third for model dependence. We also describe a new analysis performed to search for CP asymmetry in $b \to s γ$ decays. We observe no such asymmetry and set conservative limits at $-0.09 <$ $\cal{A}$ $< 0.42$.

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arXiv1999

Study of charmless hadronic B decays into the final states $Kπ, ππ$, and KK, with the first observation of $B \to π^+ π^-$ and $B\to K^0π^0$

We have studied charmless hadronic decays of B mesons into two-body final states with kaons and pions. We present preliminary results based on 9.66 million $B\bar{B}$ pairs collected with the CLEO detector. We have made the first observation of the decay $B \to π^+π^-$, with the branching fraction of $Br(B \to π^+ π^-) = (4.7^{+1.8}_{-1.5} \pm 0.6) \times 10^{-6}$. We have also observed for the first time the decay $B \to K^0π^0$ with the branching fraction of $Br(B \to K^0 π^0) = (14.8^{+5.9+2.4}_{-5.1-3.3}) \times 10^{-6}$, thus completing the set of four $Kπ$ branching fraction measurements. We present improved measurements for the decays $B\to K^{\pm}π^{\mp}$, $B^{\pm}\to K^0π^{\pm}$, and $B^{\pm}\to K^{\pm}π^0$. We use these and other charmless hadronic B decays to make a first determination of the value of the weak phase ${\rm Arg}(V^*_{ub})=γ= {113^\circ}^{+25^\circ}_{-23^\circ}$.

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arXiv1999

Search for D0-D0bar Mixing

We report on a search for D0-D0bar mixing made by a study of the `wrong-sign' process D0 -> K+pi-. The data come from 9.0 fb^-1 of integrated luminosity of e+e- collisions at sqrt{s} approximately 10 GeV produced by CESR and accumulated with the CLEO II.V detector. We measure the time-integrated rate of the `wrong-sign' process D0 -> K+pi-, relative to that of the Cabibbo-favored D0bar -> K+pi-, to be R_ws=(0.34+-0.07+-0.06)%. By a study of the rate as a function of the decay time of the D0, we measure the rate of direct, doubly Cabibbo suppressed decay D0 -> K+pi- relative to D0bar -> K+pi-, to be R_D=(0.50+0.11-0.12+-0.08)%. The amplitudes that describe D0-D0bar mixing, x' and y' are consistent with zero. The one-dimensional limits, at the 95% C.L., that we determine are (1/2)x^'2<0.05%, and -5.9%<y'<0.3%. All results are preliminary.

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arXiv1999

Charmless Hadronic B Decays to Exclusive Final States with a $K^{*},ρ,ω$, or $ϕ$ Meson

We present results of searches for B-meson decays to charmless final states that include a K*, rho, omega, or phi meson accompanied by a second meson. Using the entire data sample of 9.7 million BBbar pairs collected with the CLEO II and CLEO II.V detectors, we observe a signal for the decay B+ -> omega pi+, and measure a branching fraction of B(B+ -> omega pi+) = (11.3^{+3.3}_{-2.9} \pm 1.5) \times 10^{-6}. We also see evidence for the decay B0 -> omega K0, and set limits for the decays B0 -> rho0 pi0 and B0 -> K*0 pi0. In addition to these new results, we also summarize previous CLEO results on related channels. All quoted results are preliminary.

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arXiv1999

Two-Body B Meson Decays to $η$ and $η^{'}$ - Observation of $B\to ηK^{*}$

In a sample of 19 million produced B mesons we have observed decays B -> eta K*, and improved our previous measurements of B -> eta' K. The branching fractions we measure for these decay modes are B(B+ -> eta K*+) = (27.3 +9.6 -8.2 (stat) +- 5.0 (sys)) * 10^(-6), B(B0 -> eta K*0) = (13.8 +5.5 -4.4 +- 1.7) * 10^(-6), B(B+ -> eta' K+) = (80 +10 -9 +- 8) * 10^(-6), and B(B0 -> eta' K0) = (88 +18 -16 +- 9) * 10^(-6). We have searched with comparable sensitivity for related nonstrange decays, and report upper limits for these rates. All quoted results are preliminary.

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arXiv1999

Measurement of Charge Asymmetries in Charmless Hadronic B Decay

We search for CP violating asymmetries in five charmless hadronic B meson decays using the full CLEO II and CLEO II.V data samples totalling 9.7 million BBbar events. The resulting Acp measurements have a precision that varies from +-0.12 to +-0.25 (absolute) depending on mode. No significant nonzero asymmetry is observed in any mode but 90% CL limits are strong and rule out some estimates of Acp.

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arXiv1999

Structure Functions in the Decay $τ^{\mp}\to τ^{\mp}π^{0}π^{0}ν_τ$

Using the CLEO II detector operating at the CESR e+e- collider, we have measured the structure functions in the decay tau+/- --> pi+/- pi0 pi0 nu, based on a sample corresponding to 4*10E6 produced tau-pair events. We determine the integrated structure functions, which depend only on the three pion invariant mass, as well as the structure functions differential in the Dalitz plot. We extract model independent limits on non-axial-vector contributions from the measured structure functions as less than 16.6% of the total branching fraction, at the 95% confidence level. Separating the non-axial-vector contributions into scalar and vector contributions, we measure that scalars (vectors) contribute with less than 9.4% (7.3%) to the total branching ratio, at the 95% confidence level.

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arXiv1999

Update of the Search for the Neutrinoless Decay $τ\to μγ$

We present an update of the search for the lepton family number violating decay $τ\to μγ$ using a complete CLEO II data sample of 12.6 million $τ^+τ^-$ pairs. No evidence of a signal has been found and the corresponding upper limit is $ \BR(τ\to μγ) < 1.0 \times 10^{-6} $ at 90% CL, significantly smaller than previous limits. All quoted results are preliminary.

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arXiv1999

Resonant Structure of $τ\to 3ππ^{0}ν_τ$ and $τ\to ωπν_τ$ Decays

The resonant structure of the four pion final state in the decay $τ\to 3ππ^0ν_τ$ is analyzed using 4.27 million $τ^+τ^-$ pairs collected by the CLEO II experiment. We search for second class currents in the decay $τ\to ωπν_τ$ using spin-parity analysis and establish an upper limit on the non-vector current contribution. The mass and width of the $ρ'$ resonance are extracted from a fit to the $τ\to ωπν_τ$ spectral function. A partial wave analysis of the resonant structure of the $τ\to 3ππ^0ν_τ$ decay is performed; the spectral decomposition of the four pion system is dominated by the $ωπ$ and $a_1 π$ final states.

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arXiv1999

Observation of a Broad L=1 $c\bar{q}$ State in $B^{-}\to D^{*+}π^{-}π^{-}$ at CLEO

Using 4.7 fb^-1 of data taken at CESR at energies at and near the Upsilon(4S) we have studied the decay B- -> D{*+}pi-pi- (and its conjugate). We observe a new, broad charmed meson state, which we interpret as D_J(j=1/2), in its decay to D{*+}pi-. Our preliminary results indicate the mass and width of this L=1 state to be m = (2461 +41/-3} +/-10 +/-32) MeV and Gamma = (290 +101/-79 +/-26 +/-36) MeV, with the third uncertainty associated with the parameterization of the relative strong phases. In addition we have measured several new branching fractions of charged B mesons. All quoted results are preliminary.

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arXiv1999

Observeration of Radiative Leptonic Decay of the Tau Lepton

Using 4.68 fb^{-1} of e^+e^- annihilation data collected with the CLEO II detector we have studied tau radiative decays tau --> mu nu nu gamma and tau --> e nu nu gamma. For a 10 MeV minimum photon energy in the tau rest frame, the branching fraction of a tau radiatively decaying to a muon is measured to be (3.61+-0.16+-0.35)*10^{-3}, and to an electron is (1.75+-0.06+-0.17)*10^{-2}. The branching fractions are in agreement with the Standard Model theoretical predictions. All quoted results are preliminary.

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arXiv1999

Charged Track Multiplicity in B Meson Decay

We have used the CLEO II detector to study the multiplicity of charged particles in the decays of B mesons produced at the $Υ(4S)$ resonance. Using a sample of 1.5 x 10^6 B meson pairs, we find the mean inclusive charged particle multiplicity to be 10.71 +- 0.02 +0.21/-0.15 for the decay of the pair. This corresponds to a mean multiplicity of 5.36 +- 0.01 +0.11/-0.08 for a single B meson. Using the same data sample, we have also extracted the mean multiplicities in semileptonic and nonleptonic decays. We measure a mean of 7.82 +- 0.05 +0.21/-0.19 charged particles per $B\bar{B}$ decay when both mesons decay semileptonically. When neither B meson decays semileptonically, we measure a mean charged particle multiplicity of 11.62 +- 0.04 +0.24/-0.18 per $B\bar{B}$ pair.

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arXiv1998

Improved Measurement of the Pseudoscalar Decay Constant $f_{D_{s}}$

We present a new determination of the Ds decay constant, f_{Ds} using 5 million continuum charm events obtained with the CLEO II detector. Our value is derived from our new measured ratio of widths for Ds -> mu nu/Ds -> phi pi of 0.173+/- 0.021 +/- 0.031. Taking the branching ratio for Ds -> phi pi as (3.6 +/- 0.9)% from the PDG, we extract f_{Ds} = (280 +/- 17 +/- 25 +/- 34){MeV}. We compare this result with various model calculations.

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arXiv1998

Two-Body B Meson Decays to $η$ and $η^{'}$ -- Observation of $B\to η${'}K$

In a sample of 6.6 million produced B mesons we have observed decays B -> eta' K, with branching fractions BR(B+ -> eta' K+ = 6.5 +1.5 -1.4 +- 0.9) x $10^{-5}$ and BR(B0 -> eta' K0 = 4.7 +2.7 -2.0 +- 0.9) x $10^{-5}$. We have searched with comparable sensitivity for 17 related decays to final states containing an eta or eta' meson accompanied by a single particle or low-lying resonance. Our upper limits for these constrain theoretical interpretations of the B -> eta' K signal.

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arXiv1998

Measurement of the Branching Ratios for the Decays of $D_{s}^{+}\to ηπ^{+}, η^{'}π^{+}, ηρ^{+}$, and $eta^{'}ρ^{+}$

Using a data sample with integrated luminosity of about 3.9 fb^{-1} collected in e+ e- annihilation with the CLEO-II detector at the Cornell Electron Storage Ring, we have measured the branching ratios for the decay modes Ds -> (eta, eta') pi and Ds -> (eta, eta') rho relative to Ds -> phi pi. These decay modes are among the most common hadronic decays of the Ds's and can be related by factorization to the semileptonic decays Ds -> (eta,eta') l nu. The results obtained are compared with previous CLEO results and with the branching ratios measured for the related semileptonic decays. We also report results on the Cabibbo-suppressed decays of the D+ to the same final states.

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arXiv1997

Measurement of $Br(D^{0}\to K^{-}π^{+})$ using Partila Reconstruction of $\bar{B}\to D^{*+}X\ell^{-}\barν$

We present a measurement of the absolute branching fraction for $D^0 -> K^- pi^+$ using the reconstruction of the decay chain $Bbar -> D^{*+} X l^- nubar $, $D^{*+} -> D^0 pi^+$ where only the lepton and the low-momentum pion from the $D^{*+}$ are detected. With data collected by the CLEO II detector at the Cornell Electron Storage Ring, we have determined $Br(D^0 -> K^- pi^+)= [3.81 +- 0.15(stat.) +- 0.16(syst.)]%$.

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