4,676 research outputs found

    Measuring Strong and Weak Phases in Time-Independent B Decays

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    Flavor SU(3) symmetry implies certain relations among BB-decay amplitudes to ππ\pi\pi, πK\pi K and KKˉK {\bar K} final states, when annihilation-like diagrams are neglected. Using three triangle relations, we show how to measure the weak CKM phases α\alpha and γ\gamma using time-independent rate measurements only. In addition, one obtains all the strong final-state phases and the magnitudes of individual terms describing tree (spectator), color-suppressed and penguin diagrams. Many independent measurements of these quantities can be made with this method, which helps to eliminate possible discrete ambiguities and to estimate the size of SU(3)-breaking effects.Comment: 2 figures available from the authors upon request, 12 pages,UdeM-LPN-TH-94-19

    About the modern "experimental value" of W boson width.

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    It is shown that the methods which have been used up to now to determine the WW width from the ppˉp\bar p data confirm the SM predictions for some combinations of various phenomenological parameters, however, they do not give an independent value for the WW width. Moreover, the accuracy that could be achieved in future experimental checks of SM predictions for such quantities is limited by effects which require detailed theoretical study.Comment: Latex, 8 pages

    Combustion system processes leading to corrosive deposits

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    Degradation of turbine engine hot gas path components by high temperature corrosion can usually be associated with deposits even though other factors may also play a significant role. The origins of the corrosive deposits are traceable to chemical reactions which take place during the combustion process. In the case of hot corrosion/sulfidation, sodium sulfate was established as the deposited corrosive agent even when none of this salt enters the engine directly. The sodium sulfate is formed during the combustion and deposition processes from compounds of sulfur contained in the fuel as low level impurities and sodium compounds, such as sodium chloride, ingested with intake air. In other turbine and power generation situations, corrosive and/or fouling deposits can result from such metals as potassium, iron, calcium, vanadium, magnesium, and silicon

    Enhancement of the upper critical field in codoped iron-arsenic high-temperature superconductors

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    We present the first study of codoped iron-arsenide superconductors of the 122 family (Sr/Ba)_(1-x)K_xFe_(2-y)Co_yAs_2 with the purpose to increase the upper critical field H_c2 compared to single doped (Sr/Ba)Fe_2As_2 materials. H_c2 was investigated by measuring the magnetoresistance in high pulsed magnetic fields up to 64 T. We find, that H_c2 extrapolated to T = 0 is indeed enhanced significantly to ~ 90 T for polycrystalline samples of Ba_0.55K_0.45Fe_1.95Co_0.05As_2 compared to ~75 T for Ba_0.55K_0.45Fe_2As_2 and BaFe_1.8Co_0.2As_2 single crystals. Codoping thus is a promising way for the systematic optimization of iron-arsenic based superconductors for magnetic-field and high-current applications.Comment: 7 pages, 5 figures, submitted to Journal of Applied Physic
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