15,691 research outputs found

    Precise Predictions for Higgs Production in Neutralino Decays in the Complex MSSM

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    Complete one-loop results are obtained for the class of processes chi^0_i->chi^0_j h_a in the MSSM where all parameters entering this process beyond lowest order are allowed to have arbitrary CP-violating phases. An on-shell renormalisation scheme is worked out for the chargino-neutralino sector that properly takes account of imaginary parts arising from complex parameters and from absorptive parts of loop integrals. The genuine vertex contributions to the neutralino decay amplitudes are combined with two-loop propagator-type corrections for the outgoing Higgs boson. In this way the currently most precise prediction for this class of processes is obtained. The numerical impact of the genuine vertex corrections is studied for several examples of CP-conserving and CP-violating scenarios. We find that significant effects on the decay widths and branching ratios are possible even in the CP-conserving MSSM. In the CP-violating CPX benchmark scenario the corrections to the decay width are found to be particularly large, namely, of order 45% for a Higgs mass of 40 GeV. This parameter region of the CPX scenario where a very light Higgs boson is unexcluded by present data is analysed in detail. We find that in this parameter region, which will be difficult to cover by standard Higgs search channels at the LHC, the branching ratio for the decay chi^0_2->chi^0_1 h_1 is large. This may offer good prospects to detect such a light Higgs boson in cascade decays of supersymmetric particles.Comment: 24 pages, 6 figure

    Testing and evaluation of solid lubricants for gas bearings

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    The testing and results of testing solid film lubricants for gas lubricated bearing applications are reported. The tests simulated operational hazards of tilting pad gas bearings. The presence of a low coefficient of friction and the endurance of the solid film lubricant were the criteria for judging superior performance. All solid lubricants tested were applied to a plasma sprayed chrome oxide surface. Molybdenum disulfide and graphite fluoride were the solid lubricants tested; other test parameters included the method of application of the solid lubricant and the surface finish of the plasma sprayed coating. In general, the application of a solid film lubricant was found to significantly improve the coefficient of friction of the rubbing surfaces

    White primer permits a corrosion-resistant coating of minimum weight

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    White primer for coating 2219 aluminum alloy supplies a base for a top coating of enamel. A formulation of pigments and vehicle results in a primer with high corrosion resistance and minimum film thickness

    Are the reactions γγVV\gamma\gamma\to VV' a challenge for the factorized Pomeron at high energies?

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    We would like to point to the strong violation of the putative factorized Pomeron exchange model in the reactions γγVV\gamma\gamma\to VV' in the high-energy region where this model works fairly well in all other cases.Comment: 4 pages, LaTex, 1 fig. in postscript, minor typos corrected, to be published in Phys. Rev. D 60, 117503 (1999

    Curvature Constraints from the Causal Entropic Principle

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    Current cosmological observations indicate a preference for a cosmological constant that is drastically smaller than what can be explained by conventional particle physics. The Causal Entropic Principle (Bousso, {\it et al}.) provides an alternative approach to anthropic attempts to predict our observed value of the cosmological constant by calculating the entropy created within a causal diamond. We have extended this work to use the Causal Entropic Principle to predict the preferred curvature within the "multiverse". We have found that values larger than ρk=40ρm\rho_k = 40\rho_m are disfavored by more than 99.99% and a peak value at ρΛ=7.9×10123\rho_{\Lambda} = 7.9 \times 10^{-123} and ρk=4.3ρm\rho_k =4.3 \rho_m for open universes. For universes that allow only positive curvature or both positive and negative curvature, we find a correlation between curvature and dark energy that leads to an extended region of preferred values. Our universe is found to be disfavored to an extent depending the priors on curvature. We also provide a comparison to previous anthropic constraints on open universes and discuss future directions for this work.Comment: 5 pages, 3 Figure

    Varying c cosmology and Planck value constraints

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    It has been suggested that by increasing the speed of light during the early universe various cosmological problems of standard big bang cosmology can be overcome, without requiring an inflationary phase. However, we find that as the Planck length and Planck time are then made correspondingly smaller, and together with the need that the universe should not re-enter a Planck epoch, the higher cc models have very limited ability to resolve such problems. For a constantly decreasing cc the universe will quickly becomes quantum gravitationally dominated as time increases: the opposite to standard cosmology where quantum behaviour is only ascribed to early times.Comment: extended versio
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