2,300 research outputs found

    Bovine oocytes in secondary follicles grow and acquire meiotic competence in severe combined immunodeficient mice

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    A rigorous methodology is developed that addresses numerical and statistical issues when developing group contribution (GC) based property models such as regression methods, optimization algorithms, performance statistics, outlier treatment, parameter identifiability, and uncertainty of the prediction. The methodology is evaluated through development of a GC method for the prediction of the heat of combustion (Δ<i>H</i><sub>c</sub><sup>o</sup>) for pure components. The results showed that robust regression lead to best performance statistics for parameter estimation. The bootstrap method is found to be a valid alternative to calculate parameter estimation errors when underlying distribution of residuals is unknown. Many parameters (first, second, third order group contributions) are found unidentifiable from the typically available data, with large estimation error bounds and significant correlation. Due to this poor parameter identifiability issues, reporting of the 95% confidence intervals of the predicted property values should be mandatory as opposed to reporting only single value prediction, currently the norm in literature. Moreover, inclusion of higher order groups (additional parameters) does not always lead to improved prediction accuracy for the GC-models; in some cases, it may even increase the prediction error (hence worse prediction accuracy). However, additional parameters do not affect calculated 95% confidence interval. Last but not least, the newly developed GC model of the heat of combustion (Δ<i>H</i><sub>c</sub><sup>o</sup>) shows predictions of great accuracy and quality (the most data falling within the 95% confidence intervals) and provides additional information on the uncertainty of each prediction compared to other Δ<i>H</i><sub>c</sub><sup>o</sup> models reported in literature

    B Physics at the Tevatron: Run II and Beyond

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    This report provides a comprehensive overview of the prospects for B physics at the Tevatron. The work was carried out during a series of workshops starting in September 1999. There were four working groups: 1) CP Violation, 2) Rare and Semileptonic Decays, 3) Mixing and Lifetimes, 4) Production, Fragmentation and Spectroscopy. The report also includes introductory chapters on theoretical and experimental tools emphasizing aspects of B physics specific to hadron colliders, as well as overviews of the CDF, D0, and BTeV detectors, and a Summary.Comment: 583 pages. Further information on the workshops, including transparencies, can be found at the workshop's homepage: http://www-theory.lbl.gov/Brun2/. The report is also available in 2-up http://www-theory.lbl.gov/Brun2/report/report2.ps.gz or chapter-by-chapter http://www-theory.lbl.gov/Brun2/report

    Master crossover behavior of parachor correlations for one-component fluids

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    The master asymptotic behavior of the usual parachor correlations, expressing surface tension σ\sigma as a power law of the density difference ρLρV\rho_{L}-\rho_{V} between coexisting liquid and vapor, is analyzed for a series of pure compounds close to their liquid-vapor critical point, using only four critical parameters (βc)1(\beta_{c})^{-1}, αc\alpha_{c}, ZcZ_{c} and YcY_{c}, for each fluid. ... The main consequences of these theoretical estimations are discussed in the light of engineering applications and process simulations where parachor correlations constitute one of the most practical method for estimating surface tension from density and capillary rise measurements

    Suppressed Decays of D_s^+ Mesons to Two Pseudoscalar Mesons

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    Using data collected near the Ds*+ Ds- peak production energy Ecm = 4170 MeV by the CLEO-c detector, we study the decays of Ds+ mesons to two pseudoscalar mesons. We report on searches for the singly-Cabibbo-suppressed Ds+ decay modes K+ eta, K+ eta', pi+ K0S, K+ pi0, and the isospin-forbidden decay mode Ds+ to pi+ pi0. We normalize with respect to the Cabibbo-favored Ds+ modes pi+ eta, pi+ eta', and K+ K0S, and obtain ratios of branching fractions: Ds+ to K+ eta / Ds+ to pi+ eta = (8.9 +- 1.5 +- 0.4)%, Ds+ to K+ eta' / Ds+ to pi+ eta' = (4.2 +- 1.3 +- 0.3)%, Ds+ to pi+ K0S / Ds+ to K+ K0S = (8.2 +- 0.9 +- 0.2)%, Ds+ to K+ pi0 / Ds+ to K+ K0S = (5.0 +- 1.2 +- 0.6)%, and Ds+ to pi+ pi0 / Ds+ to K+ K0S < 4.1% at 90% CL, where the uncertainties are statistical and systematic, respectively.Comment: 9 pages postscript,also available through http://www.lns.cornell.edu/public/CLNS/2007/, Submitted to PR

    Determination of the D0 -> K+pi- Relative Strong Phase Using Quantum-Correlated Measurements in e+e- -> D0 D0bar at CLEO

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    We exploit the quantum coherence between pair-produced D0 and D0bar in psi(3770) decays to study charm mixing, which is characterized by the parameters x and y, and to make a first determination of the relative strong phase \delta between doubly Cabibbo-suppressed D0 -> K+pi- and Cabibbo-favored D0bar -> K+pi-. We analyze a sample of 1.0 million D0D0bar pairs from 281 pb^-1 of e+e- collision data collected with the CLEO-c detector at E_cm = 3.77 GeV. By combining CLEO-c measurements with branching fraction input and time-integrated measurements of R_M = (x^2+y^2)/2 and R_{WS} = Gamma(D0 -> K+pi-)/Gamma(D0bar -> K+pi-) from other experiments, we find \cos\delta = 1.03 +0.31-0.17 +- 0.06, where the uncertainties are statistical and systematic, respectively. In addition, by further including external measurements of charm mixing parameters, we obtain an alternate measurement of \cos\delta = 1.10 +- 0.35 +- 0.07, as well as x\sin\delta = (4.4 +2.7-1.8 +- 2.9) x 10^-3 and \delta = 22 +11-12 +9-11 degrees.Comment: 37 pages, also available through http://www.lns.cornell.edu/public/CLNS/2007/. Incorporated referee's comment

    Measurement of \cal{B}(D^+ --> mu^+ nu) and the Pseudoscalar Decay Constant fD+f_{D^+}

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    In 60 pb-1 of data taken on the psi(3770) resonance with the CLEO-c detector, we find 8 D+ to mu+ nu event candidates that are mostly signal, containing only 1 estimated background. Using this statistically compelling sample, we measure preliminary values of B(D+ to mu+ nu) = (3.5 +- 1.4 +- 0.6)*10^{-4}, and determine f_{D+} =(201+- 41+- 17) MeV.Comment: 17 pages postscript, also available through http://www.lns.cornell.edu/public/CONF/2004/, Presented at ICHEP Aug 16-22,2004, Beijing, Chin

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

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    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.Comment: 10 pages postscript,also available through http://www.lns.cornell.edu/public/CLNS/2007/, Submitted to PR

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

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    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.Comment: 6 pages postscript,also available through http://www.lns.cornell.edu/public/CLNS/2007

    Update of the measurement of the cross section for e^+e^- -> psi(3770) -> hadrons

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    We have updated our measurement of the cross section for e^+e^- -> psi(3770) -> hadrons, our publication "Measurement of sigma(e^+e^- -> psi(3770) -> hadrons) at E_{c.m.} = 3773 MeV", arXiv:hep-ex/0512038, Phys.Rev.Lett.96, 092002 (2006). Simultaneous with this arXiv update, we have published an erratum in Phys.Rev.Lett.104, 159901 (2010). There, and in this update, we have corrected a mistake in the computation of the error on the difference of the cross sections for e^+e^- -> psi(3770) -> hadrons and e^+e^- -> psi(3770) -> DDbar. We have also used a more recent CLEO measurement of cross section for e^+e^- -> psi(3770) -> DDbar. From this, we obtain an upper limit on the branching fraction for psi(3770) -> non-DDbar of 9% at 90% confidence level.Comment: 3 pages, 0 figures. This is an erratum to Phys.Rev.Lett.96:092002,2006. Added a reference

    Measurement of Charm Production Cross Sections in e+e- Annihilation at Energies between 3.97 and 4.26 GeV

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    Using the CLEO-c detector at the Cornell Electron Storage Ring, we have measured inclusive and exclusive cross sections for the production of D+, D0 and Ds+ mesons in e+e- annihilations at thirteen center-of-mass energies between 3.97 and 4.26 GeV. Exclusive cross sections are presented for final states consisting of two charm mesons (DD, D*D, D*D*, Ds+Ds-, Ds*+Ds-, and Ds*+Ds*-) and for processes in which the charm-meson pair is accompanied by a pion. No enhancement in any final state is observed at the energy of the Y(4260).Comment: 19 pages, postscript also available through http://www.lns.cornell.edu/public/CLNS/2007/, Submitted to PR
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