106,136 research outputs found

    Efficient Estimation of a Dynamic Error-Shock Model

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    This paper is concerned with the estimation of the parameters in a dynamic simultaneous equation model with stationary disturbances under the assumption that the variables are subject to random measurement errors. The conditions under which the parameters are identified are stated. An asymptotically efficient frequency-domain class of instrumental variables estimators is suggested. The procedure consists of two basic steps. The first step transforms the model in such a way that the observed exogenous variables are asymptotically orthogonal to the residual terms. The second step involves an iterative procedure like that of Robinson [13].

    Bounds on R-parity violating supersymmetric couplings from leptonic and semi-leptonic meson decays

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    We present a comprehensive update of the bounds on R-Parity violating supersymmetric couplings from lepton-flavour- and lepton-number-violating decay processes. We consider tau and mu decays as well as leptonic and semi-leptonic decays of mesons. We present several new bounds resulting from tau, eta and Kaon decays and correct some results in the literature concerning B-meson decays.Comment: 30 pages; changed title, updated some bounds from the literature from different references, added reference

    As-built design specification for MISMAP

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    The MISMAP program, which is part of the CLASFYT package, is described. The program is designed to compare classification values with ground truth values for a segment and produce a comparison map and summary table

    Hadronic B Decays to Charmed Baryons

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    We study exclusive B decays to final states containing a charmed baryon within the pole model framework. Since the strong coupling for ΛbBˉN\Lambda_b\bar B N is larger than that for ΣbBˉN\Sigma_b \bar BN, the two-body charmful decay BΣc0pˉB^-\to\Sigma_c^0\bar p has a rate larger than Bˉ0Λc+pˉ\bar B^0\to\Lambda_c^+\bar p as the former proceeds via the Λb\Lambda_b pole while the latter via the Σb\Sigma_b pole. By the same token, the three-body decay Bˉ0Σc++pˉπ\bar B^0\to\Sigma_c^{++}\bar p\pi^- receives less baryon-pole contribution than BΛc+pˉπB^-\to\Lambda_c^+\bar p\pi^-. However, because the important charmed-meson pole diagrams contribute constructively to the former and destructively to the latter, Σc++pˉπ\Sigma_c^{++}\bar p\pi^- has a rate slightly larger than Λc+pˉπ\Lambda_c^+\bar p\pi^-. It is found that one quarter of the BΛc+pˉπB^-\to \Lambda_c^+\bar p\pi^- rate comes from the resonant contributions. We discuss the decays Bˉ0Σc0pˉπ+\bar B^0\to\Sigma_c^0\bar p\pi^+ and BΣc0pˉπ0B^-\to\Sigma_c^0\bar p\pi^0 and stress that they are not color suppressed even though they can only proceed via an internal W emission.Comment: 25 pages, 6 figure

    One-loop quantum corrections to cosmological scalar field potentials

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    We study the loop corrections to potentials of complex or coupled real scalar fields used in cosmology to account for dark energy, dark matter or dark fluid. We show that the SUGRA quintessence and dark matter scalar field potentials are stable against the quantum fluctuations, and we propose solutions to the instability of the potentials of coupled quintessence and dark fluid scalar fields. We also find that a coupling to fermions is very restricted, unless this coupling has a structure which already exists in the scalar field potential or which can be compensated by higher order corrections. Finally, we study the influence of the curvature and kinetic term corrections.Comment: 11 pages, 1 figure, accepted for publication in Phys. Rev.

    Analysis of B-> \phi K Decays in QCD Factorization

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    We analyze the decay BϕKB\to \phi K within the framework of QCD-improved factorization. We found that although the twist-3 kaon distribution amplitude dominates the spectator interactions, it will suppress the decay rates slightly. The weak annihilation diagrams induced by (SP)(S+P)(S-P)(S+P) penguin operators, which are formally power-suppressed by order (Λ/mb)2(\Lambda/m_b)^2, are chirally and logarithmically enhanced. Therefore, these annihilation contributions are not subject to helicity suppression and can be sizable. The predicted branching ratio of BϕKB^-\to\phi K^- is (3.8±0.6)×106(3.8\pm0.6)\times 10^{-6} in the absence of annihilation contributions and it becomes (4.31.4+3.0)×106(4.3^{+3.0}_{-1.4})\times 10^{-6} when annihilation effects are taken into account. The prediction is consistent with CLEO and BaBar data but smaller than the BELLE result.Comment: 13 pages, 3 figures. A major change for the presentation of branching-ratio predictions. Experimental data are update

    Cross-section and polarization of neutrino-produced τ\tau's made simple

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    Practical formulae are derived for the cross-section and polarization of the τ\tau lepton produced in deep-inelastic neutrino-nucleon scattering in the frame of the simple quark-parton model.Comment: 10 pages, no figure

    Chiral transition and deconfinement transition in QCD with the highly improved staggered quark (HISQ) action

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    We report preliminary results on the chiral and deconfinement aspects of the QCD transition at finite temperature using the Highly Improved Staggered Quark (HISQ) action on lattices with temporal extent of N_{\tau}=6 and 8. The chiral aspects of the transition are studied in terms of quark condensates and the disconnected chiral susceptibility. We study the deconfinement transition in terms of the strange quark number susceptibility and the renormalized Polyakov loop. We made continuum estimates for some quantities and find reasonably good agreement between our results and the recent continuum extrapolated results obtained with the stout staggered quark action.Comment: Talk presented by P. Petreczky at workshop Dense Matter 2010, April 6-9, Stellenbosch, South Africa, to be published in the proceeding

    Quantum Noise in the Collective Abstraction Reaction A+B 2_2\to AB+B

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    We demonstrate theoretically that the collective abstraction reaction A+B2_2 \to AB+B can be realized efficiently with degenerate bosonic or fermionic matter waves. We show that this is dominated by quantum fluctuations, which are critical in triggering its initial stages with the appearance of macroscopic non-classical correlations of the atomic and molecular fields as a result. This study opens up a promising new regime of quantum degenerate matter-wave chemistry.Comment: 4 pages, 3 figures, publishe
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