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CLEO Collaboration

Publications and source records attributed to CLEO Collaboration.

At least 73 records · Page 4Linked to original sources
arXiv2007

A Study of the Decays D^0 --> pi^- e^+ nu_e, D^0 --> K^- e^+ nu_e, D^+ --> pi^0 e^+ nu_e, and D^+ --> barK^0 e^+ nu_e

Using 1.8 million DDbar pairs and a neutrino reconstruction technique, we have studied the decays D^0 -> K^- e^+ nu_e, D^0 -> pi^- e^+ nu_e, D^+ -> Kbar^0 e^+ nu_e, and D^+ -> pi^0 e^+ nu_e. We find B(D^0 -> pi^- e^+ nu_e) = 0.299(11)(9)%, B(D^+ -> pi^0 e^+ nu_e) = 0.373(22)(13)%, B(D^0 -> K^- e^+ nu_e) = 3.56(3)(9)%, and B(D^+ -> Kbar^0 e^+ nu_e) = 8.53(13)(23)%. In addition, form factors are studied through fits to the partial branching fractions obtained in five q^2 ranges. By combining our results with recent unquenched lattice calculations, we obtain |Vcd| = 0.217(9)(4)(23) and |Vcs| = 1.015(10)(11)(106).

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arXiv2007

Measurement of Absolute Hadronic Branching Fractions of D Mesons and e^+ e^- --> D D-bar Cross Sections at the psi(3770)

Using 281 /pb of e^+ e^- collisions recorded at the psi(3770) resonance with the CLEO-c detector at CESR, we determine absolute hadronic branching fractions of charged and neutral D mesons using a double tag technique. Among measurements for three D^0 and six D^+ modes, we obtain reference branching fractions B(D^0 --> K^-pi^+) = (3.891 +- 0.035 +- 0.059 +- 0.035)% and B(D^+ --> K^-pi^+pi^+) = (9.14 +- 0.10 +- 0.16 +- 0.07)%, where the first uncertainty is statistical, the second is all systematic errors other than final state radiation (FSR), and the third is the systematic uncertainty due to FSR. We include FSR in these branching fractions by allowing for additional unobserved photons in the final state. Using an independent determination of the integrated luminosity, we also extract the cross sections sigma(e+e- --> D^0 D^0-bar) = (3.66+- 0.03 +- 0.06) nb and sigma(e+e- --> D^+ D^-) = (2.91+- 0.03 +- 0.05) nb at a center of mass energy, E_cm = 3774 +- 1 MeV.

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arXiv2007

Measurement of the eta-Meson Mass using psi(2S) --> eta J/psi

We measure the mass of the eta meson using psi(2S) --> eta J/psi events acquired with the CLEO-c detector operating at the CESR e+e- collider. Using the four decay modes eta --> gamma gamma, 3pi0, pi+pi-pi0, and pi+pi-gamma, we find M(eta)=547.785 +- 0.017 +- 0.057 MeV, in which the first uncertainty is statistical and the second systematic. This result has an uncertainty comparable to the two most precise previous measurements and is consistent with that of NA48, but is inconsistent at the level of 6.5sigma with the much smaller mass obtained by GEM.

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arXiv2007

Di-electron Widths of the Upsilon(1S,2S,3S) Resonances

We determine the di-electron widths of the Upsilon(1S), Upsilon(2S), and Upsilon(3S) resonances with better than 2% precision by integrating the cross-section of e+e- -> Upsilon over the e+e- center-of-mass energy. Using e+e- energy scans of the Upsilon resonances at the Cornell Electron Storage Ring and measuring Upsilon production with the CLEO detector, we find di-electron widths of 1.354 +- 0.004 (stat) +- 0.020 (syst) keV, 0.619 +- 0.004 +- 0.010 keV, and 0.446 +- 0.004 +- 0.007 keV for the Upsilon(1S), Upsilon(2S), and Upsilon(3S), respectively.

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arXiv2007

Measurement of the Decay Constant $f_D{_S^+}$ using $D_S^+ --> ell^+ nu

We measure the decay constant fDs using the Ds -> l+ nu channel, where the l+ designates either a mu+ or a tau+, when the tau+ -> pi+ nu. Using both measurements we find fDs = 274 +-13 +- 7 MeV. Combining with our previous determination of fD+, we compute the ratio fDs/fD+ = 1.23 +- 0.11 +- 0.04. We compare with theoretical estimates.

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arXiv2007

Measurement of B(D_S^+ --> ell^+ nu) and the Decay Constant f_D_{S^+}

We examine e+e- --> Ds- Ds*+ and Ds*- Ds+ interactions at 4170 MeV using the CLEO-c detector in order to measure the decay constant fDs+. We use the Ds+ --> l+ nu channel, where the l+ designates either a mu+ or a tau+, when the tau+ --> pi+ nu. Analyzing both modes independently, we determine B(Ds+ --> mu+ nu) = (0.594 +- 0.066 +- 0.031)%, and B(Ds+ --> tau+ nu) = (8.0 +- 1.3 +- 0.4)%. We also analyze them simultaneously to find an effective value of B{eff}(Ds+ --> mu+ nu) = (0.638 +- 0.059 +- 0.033)% and extract fDs = (274 +- 13 +- 7) MeV. Combining with our previous determination of B(D+ -> mu+ nu), we also find the ratio fDs/fD+ = 1.23 +- 0.11 +- 0.04. We compare to current theoretical estimates. Finally, we find B(Ds+ --> e+ nu) < 1.3 x10^{-4} at 90% confidence level.

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arXiv2007

Study of Di-Pion Transitions Among Upsilon(3S), Upsilon(2S), and Upsilon(1S) States

We present measurements of decay matrix elements for hadronic transitions of the form Upsilon(nS) -> pi pi Upsilon(mS) where (n, m) = (3, 1), (2, 1), and (3, 2). We reconstruct charged and neutral pion modes with the final state Upsilon decaying to either mu+mu- or e+e-. Dalitz plot distributions for the twelve decay modes are fit individually as well as jointly assuming isospin symmetry, thereby measuring the matrix elements of the decay amplitude. We observe and account for the anomaly previously noted in the di-pion invariant mass distribution for the Upsilon(3S) -> pi pi Upsilon(1S) transition and obtain good descriptions of the dynamics of the decay using the most general decay amplitude allowed by partial conservation of the axial-vector current (PCAC) considerations. The fits further indicate that the Upsilon(2S) -> pi pi Upsilon(1S) and Upsilon(3S) -> pi pi Upsilon(2S) transitions also show the presence of terms in the decay amplitude that were previously ignored, although at a relatively suppressed level.

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arXiv2007

Measurement of Prominent eta Decay Branching Fractions

The decay psi(2S) --> eta J/psi is used to measure, for the first time, all prominent eta-meson branching fractions with the same experiment in the same dataset, thereby providing a consistent treatment of systematics across branching fractions. We present results for eta decays to gamma gamma, pi+pi-pi0, 3 pi0, pi+ pi- gamma, and e+ e- gamma, accounting for 99.9% of all eta decays. The precisions for several of the branching fractions and their ratios are improved. Two channels, pi+ pi- gamma and e+ e- gamma, show results that differ at the level of three standard deviations from those previously determined.

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arXiv2007

Dalitz Plot Analysis of the D+ --> pi- pi+ pi+ Decay

Using 281 pb^{-1} of data recorded by the CLEO-c detector in e^+e^- collisions at the psi(3770), corresponding to 0.78 million D^+D^- pairs, we investigate the substructure of the decay D^+ to pi^- pi^+ pi^+ using the Dalitz plot technique. We find that our data are consistent with the following intermediate states: rho(770)pi^+, f_2(1270)pi^+, f_0(1370)pi^+, f_0(1500)pi^+, f_0(980) pi^+, and sigma pi^+. We confirm large S wave contributions at low pi pi mass. We set upper limits on contributions of other possible intermediate states. We consider three models of the pi pi S wave and find that all of them adequately describe our data.

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arXiv2007

Evidence for the Decay D^0 --> K^_pi^+pi^-e^+nu_e

Using a 281 pb^{-1} data sample collected at the psi(3770) with the CLEO-c detector, we present the first absolute branching fraction measurement of the decay D^0 rightarrow K^-pi^+pi^-e^+nu_e at a statistical significance of about 4.0 standard deviations. We find 10 candidates consistent with the decay D^0 rightarrow K^-pi^+pi^- e^+nu_e. The probability that a background fluctuation accounts for this signal is less than 4.1 times 10^{-5}. We find {cal B}(D^0 rightarrow K^-pi^+pi^-e^+nu_e)= [2.8 ^{+1.4}_{-1.1}{rm (stat)} pm 0.3{rm (syst)}] times 10 ^{-4}. This channel is consistent with being predominantly produced through D^0 rightarrow K1^- e^+nu_e. By restricting the invariant mass of the hadronic system to be consistent with K1, we obtain the product of branching fractions {cal B}(D^0 rightarrow K1^- e^+nu_e)cdot{\cal B}(K1 to K^-pi^+pi^-)=[2.5^{+1.3}_{-1.0}{rm(stat)} pm 0.2 {rm (syst)}]times 10^{-4}. Using {cal B}(K1 to K^-pi^+pi^-) = (33 pm 3) %, we obtain {cal B}(D^0 to K1^-e^+nu_e)=[7.6^{+4.1}_{-3.0}{rm (stat)} pm 0.6{rm (syst)}pm 0.7 ]times 10^{-4}. The last error accounts for the uncertainties in the measured konem to K^-pi^+pi^- branching fraction.

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arXiv2007

Search for Radiative Decays of Upsilon(1S) into eta and eta'

We report on a search for the radiative decay of Upsilon(1S) to the pseudoscalar mesons eta and etaprime in 21.2 +/- 0.2 times 10^6 Upsilon(1S) decays collected with the CLEO III detector at the Cornell Electron Storage Ring (CESR). The eta meson was reconstructed in the three modes eta to gamma-gamma, eta to pi+pi-pi0 and eta to 3pi0. The etaprime meson was reconstructed in the mode etaprime to pi+ pi- eta with eta decaying through any of the above three modes, and also etaprime to gamma rho, where rho decays to pi^+ pi^-. Five out of the seven sub-modes are found to be virtually background-free. In four of them we find no signal candidates and in one Upsilon(1S) to gamma-etaprime, etaprime to pi+ pi- eta, eta to pi+pi-pi0 there are two good signal candidates, which is insufficient evidence to claim a signal. The other two sub-modes eta to gamma-gamma and etaprime to gamma rho are background limited, and show no excess of events in their signal regions. We combine the results from different channels and obtain upper limits at the 90% C.L. which are B(Upsilon(1S) to gamma eta) < 1.0 times 10^-6 and B(Upsilon(1S) to gamma etaprime) < 1.9 times 10^-6. Our limits are an order of magnitude tighter than the previous ones and below the predictions made by some theoretical models.

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arXiv2007

Measurement of Upper Limits for Upsilon --> gamma + R Decays

Motivated by concerns regarding possible two-body contributions to the recently-measured inclusive Upsilon(nS)->gamma+X (n=1, 2, 3) direct photon spectra, we report on a new study of exclusive radiative decays of these narrow Upsilon(nS) resonances into two-body final states R+gamma, with R a narrow resonant hadronic state decaying into four or more charged particles. Such two-body processes are not explicitly addressed in the extant theoretical frameworks used to calculate the inclusive direct photon spectra, and must also be explicitly inserted into Monte Carlo simulations. Using data collected from the CLEO III detector at the Cornell Electron Storage Ring, we present upper limits of order 0.01 per cent for such bottomonium two-body decays as a function of the R recoil mass.

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arXiv2007

chi_c0 and chi_c2 Decays into eta eta, eta eta', and eta' eta' Final States

Using a sample of 3 x 10^6 psi(2S) decays collected by the CLEO III and CLEO_c detector configurations, we present results of a study of χ_{c0} and χ_{c2} decays into eta-eta, eta-etaprime, and etaprime-etaprime final states. We find B(chi_{c0} -> eta-eta)= (0.31+-0.05+-0.04+-0.02)%, B(chi_{c0} -> eta-etaprime) <0.05 % at the 90% confidence level, and B(chi_{c0} -> etaprime-etaprime) = (0.17 +- 0.04 +-0.02 +-0.01)%. We also present upper limits for the decays of χ_{c2} into these final states. These results give information on the decay mechanism of χ_c states into pseudoscalars.

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arXiv2007

Search for D^0 - barD^0 Mixing in the Dalitz Plot Analysis of D^0 --> K_S^0 pi^+ pi^-

The resonant substructure in D0 --> K0S pi+ pi- decays is described by a combination of ten quasi two-body intermediate states which include both CP-even and CP-odd eigenstates and one doubly-Cabibbo suppressed channel. We present a formalism that connects the variation in D0 decay time over the Dalitz plot with the mixing parameters, x and y, that describe off-shell and on-shell D0-D0B mixing. We analyze the CLEO II.V data sample and find the parameters x and y are consistent with zero. We limit (-4.7 < x < 8.6)% and (-6.1 < y < 3.5)% at the 95\% confidence level

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arXiv2007

First Observation of Upsilon(3S) --> tau tau and Tests of Lepton Universality in Upsilon Decays

Using data collected with the CLEO-III detector at the CESR e+e- collider, we report on a first observation of the decay of the Upsilon(3S) to tau tau, and precisely measure the ratio of branching fractions of Upsilon(nS),n=1,2,3 to tau tau and mu mu final states, finding agreement with expectations from lepton universality. We derive absolute branching fractions for these decays, and also set a limit on the influence of a low mass CP-odd Higgs boson in the decay of the Upsilon(1S).

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arXiv2007

Radiative Decays of the Upsilon(1S) to gamma pi^0 pi^0, and gamma eta eta and gamma pi^0 eta

We report on a study of exclusive radiative decays of the Upsilon(1S) resonance into the final states gamma pi^0 pi^0, gamma eta eta and gamma pi^0 eta, using 1.13 inverse femto-barn of e^+ e^- annihilation data collected at sqrt(s)= 9.46 GeV with the CLEO III detector operating at the Cornell Electron Storage Ring. In the channel gamma pi^0 pi^0, we measure the branching ratio for the decay mode Upsilon(1S) to gamma f_2(1270) to be (10.5 \pm 1.6 (+ 1.9)(-1.8)) x 10^-5. We place upper limits on the product branching ratios for the isoscalar resonances f_0(1500) and f_0(1710) for the pi^0 pi^0 and eta-eta decay channels. We also set an upper limit on the Upsilon(1S) radiative decay into pi^0 eta.

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arXiv2007

Search for Invisible Decays of the Upsilon(1S) Resonance

We present a measurement of the branching fraction of invisible Upsilon(1S) decays, using 1.2 fb^{-1} of data collected at the Upsilon(2S) resonance with the CLEO III detector at CESR. After subtracting expected backgrounds from events that pass selection criteria for invisible Upsilon(1S) decay in Upsilon(2S) -> pi+ pi- Upsilon(1S), we deduce a 90% C.L. upper limit of B[Upsilon(1S) -> invisible] < 0.39%.

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