The CLEO-III Ring Imaging Cherenkov Detector

The CLEO-III Detector upgrade for charged particle identification is discussed. The RICH design uses solid LiF crystal radiators coupled with multi-wire chamber photon detectors, using TEA as the photosensor, and low-noise Viking readout electronics. Results from our beam test at Fermilab are presented.Comment: Invited talk by R.J. Mountain at ``The 3rd International Workshop on Ring Imaging Cherenkov Detectors," a research workshop of the Israel Science Foundation, Ein-Gedi, Dead-Sea, Israel, Nov. 15-20, 1998, 14 pages, 9 figure

Recurrent early filter clotting during continuous veno-venous hemodialysis with regional citrate anticoagulation is linked to systemic thrombin generation and heparin induced thrombocytopenia type II: a retrospective analysis

OBJECTIVE: Regional citrate anticoagulation (RCA) for continuous renal replacement therapy (CRRT) is widely used and leads to an excellent clottingfree filter survival. Despite strict adherence to protocols, in some cases recurrent early filter-clotting occurs. The aim of this observational study was to evaluate the underlying causes and the efficacy of interventions in patients with early recurrent filter-clotting during RCA. METHODS: In a retrospective analysis of a cohort of 1183 patients treated with RCA-CRRT we detected 12 patients with early filter-clotting unrelated to protocol violation or any obvious technical or medical reason. RESULTS: All patients were systemically anticoagulated with low molecular weight or unfractionated heparin for at least 24h before initiation of Continuous Veno-Venous Hemodialysis with RCA (RCA-CVVHD). During RCA, all postfilter ionized calcium concentrations were in the target range (mean 0.33±0.05 mmol/L). At the time of the first clotting event, thrombocyte counts were 168±66/ nL. After the clotting events, the systemic anticoagulation was switched to argatroban in all patients. With systemic anticoagulation using argatroban filter lifetime of RCA-CVVHD increased significantly (p<0.001) and clotting-events decreased from 0.61 to 0.10 per 24h. All patients were tested for HIT and 5/12 (42%) had a positive test for hep-PF4-antibodies. Application of argatroban significantly reduced early filter-clotting both in HIT-positive patients as well as in HIT-negative patients. At the time of the first clotting event, no patient had clinical signs of thrombosis or thromboembolism. However, during follow up a thromboembolic event occurred in three patients. CONCLUSION: In patients with recurrent early filter-clotting despite strict adherence to the citrate protocol undetected HIT or other causes of thrombin activation may be present. Therefore, patients with recurrent early filter clotting in RCA-CVVHD should be screened for HIT or other conditions that may activate thrombin. A significant improvement of filter run-time can be achieved by systemic administration of a thrombin inhibitor both in patients with and without HIT

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

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.Comment: 18 page postscript file, postscript file also available through http://w4.lns.cornell.edu/public/CLN

Search for the Decays B^0 -> D^{(*)+} D^{(*)-}

Using the CLEO-II data set we have searched for the Cabibbo-suppressed decays B^0 -> D^{(*)+} D^{(*)-}. For the decay B^0 -> D^{*+} D^{*-}, we observe one candidate signal event, with an expected background of 0.022 +/- 0.011 events. This yield corresponds to a branching fraction of Br(B^0 -> D^{*+} D^{*-}) = (5.3^{+7.1}_{-3.7}(stat) +/- 1.0(syst)) x 10^{-4} and an upper limit of Br(B^0 -> D^{*+} D^{*-}) D^{*\pm} D^\mp and B^0 -> D^+ D^-, no significant excess of signal above the expected background level is seen, and we calculate the 90% CL upper limits on the branching fractions to be Br(B^0 -> D^{*\pm} D^\mp) D^+ D^-) < 1.2 x 10^{-3}.Comment: 12 page postscript file also available through http://w4.lns.cornell.edu/public/CLNS, submitted to Physical Review Letter

Study of the B^0 Semileptonic Decay Spectrum at the Upsilon(4S) Resonance

We have made a first measurement of the lepton momentum spectrum in a sample of events enriched in neutral B's through a partial reconstruction of B0 --> D*- l+ nu. This spectrum, measured with 2.38 fb**-1 of data collected at the Upsilon(4S) resonance by the CLEO II detector, is compared directly to the inclusive lepton spectrum from all Upsilon(4S) events in the same data set. These two spectra are consistent with having the same shape above 1.5 GeV/c. From the two spectra and two other CLEO measurements, we obtain the B0 and B+ semileptonic branching fractions, b0 and b+, their ratio, and the production ratio f+-/f00 of B+ and B0 pairs at the Upsilon(4S). We report b+/b0=0.950 (+0.117-0.080) +- 0.091, b0 = (10.78 +- 0.60 +- 0.69)%, and b+ = (10.25 +- 0.57 +- 0.65)%. b+/b0 is equivalent to the ratio of charged to neutral B lifetimes, tau+/tau0.Comment: 14 page, postscript file also available at http://w4.lns.cornell.edu/public/CLN

Determination of the Michel Parameters and the tau Neutrino Helicity in tau Decay

Using the CLEO II detector at the $e^+e^-$ storage ring CESR, we have determined the Michel parameters $\rho$, $\xi$, and $\delta$ in $\tau^\mp \to l^\mp\nu\bar{\nu}$ decay as well as the tau neutrino helicity parameter $h_{\nu_\tau}$ in $\tau^\mp \to \pi^\mp\pi^0\nu$ decay. From a data sample of $3.02\times 10^6$ tau pairs produced at $\sqrt{s}=10.6 GeV$, using events of the topology $e^+e^- \to \tau^+\tau^- \to (l^\pm\nu\bar{\nu}) (\pi^\mp\pi^0\nu)$ and $e^+e^- \to \tau^+\tau^- \to (\pi^\pm\pi^0\bar{\nu}) (\pi^\mp\pi^0\nu)$, and the determined sign of $h_{\nu_\tau}$, the combined result of the three samples is: $\rho = 0.747\pm 0.010\pm 0.006$, $\xi = 1.007\pm 0.040\pm 0.015$, $\xi\delta = 0.745\pm 0.026\pm 0.009$, and $h_{\nu_\tau} = -0.995\pm 0.010\pm 0.003$. The results are in agreement with the Standard Model V-A interaction.Comment: 18 page postscript file, postscript file also available through http://w4.lns.cornell.edu/public/CLN

Improved Measurement of the Pseudoscalar Decay Constant fDsf_{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.Comment: 23 page postscript file, postscript file also available through http://w4.lns.cornell.edu/public/CLN

ΛΛˉ\Lambda\bar{\Lambda} Production in Two-Photon Interactions at CLEO

Using the CLEO detector at the Cornell $e^+e^-$ storage ring, CESR, we study the two-photon production of $\Lambda \bar{\Lambda}$, making the first observation of $\gamma \gamma \to \Lambda \bar{\Lambda}$. We present the cross-section for $\gamma \gamma \to \Lambda \bar{\Lambda}$ as a function of the $\gamma \gamma$ center of mass energy and compare it to that predicted by the quark-diquark model.Comment: 10 pages, postscript file also available through http://w4.lns.cornell.edu/public/CLN