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  1. On the extraction of P11 resonances from πN data

    Nakamura, Satoshi X. ; Lee, Tsung -Shung ; Sato, Toru - Physical Review C, Nuclear Physics
    With the accuracy of the available P11 amplitudes of πΔ scattering, we show that two resonance poles near the pi Delta threshold, obtained in several analyses, are stable against large variations of parameters within a dynamical coupled-channels analysis. The number of poles in the 1.5 GeV < W < 2 GeV region could be more than one, depending on how the structure of the single-energy solution of SAID is fitted. Lastly, our results indicate the need of more accurate πN scattering data in the W > 1.6 GeV region for high precision resonance extractions.

  2. Partial wave analysis of the reaction γ p → p ω and the search for nucleon resonances

    Williams, M. ; Applegate, D. ; Bellis, M. ; ... - Physical Review C, Nuclear Physics
    We performed an event-based partial wave analysis (PWA) of the reaction γ p -> p ω on a high-statistics dataset obtained using the CLAS at Jefferson Lab for center-of-mass energies from threshold up to 2.4 GeV. This analysis benefits from access to the world's first high precision spin density matrix element measurements, available to the event-based PWA through the decay distribution of omega-> π+ π - π0. The data confirm the dominance of the t-channel π0 exchange amplitude in the forward direction. The dominant resonance contributions are consistent with the previously identified states F[15](1680) and D[13](1700) near threshold, as wellmore » as the G[17](2190) at higher energies. Suggestive evidence for the presence of a J(P)=5/2+ state around 2 GeV, a "missing" state, has also been found. Evidence for other states is inconclusive.« less

  3. Differential cross sections for the reactions γ p → p η and γ p → p η '

    Williams, M. ; Krahn, Z. ; Applegate, D. ; ... - Physical Review C, Nuclear Physics
    In high-statistics differential cross sections for the reactions γ p -> p η and γ p -> p η' the CLAS at Jefferson Lab was used to measure the center-of-mass energies from near threshold up to 2.84 GeV. The eta-prime results are the most precise to date and provide the largest energy and angular coverage. The eta measurements extend the energy range of the world's large-angle results by approximately 300 MeV. These new data, in particular the η' measurements, are likely to help constrain the analyses being performed to search for new baryon resonance states.

  4. The extraction of Φ – N total cross section from d ( γ , p K + K - ) n

    Qian, X. ; Chen, W. ; Gao, H. ; ... - Physics Letters. B
    We report on the first measurement of the differential cross section of $$\phi$$-meson photoproduction for the $$d(\gamma,pK^{+}K^{-})n$$ exclusive reaction channel. The experiment was performed using a \textcolor{black}{tagged-photon} beam and the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. A combined analysis using data from the $$d(\gamma,pK^{+}K^{-})n$$ channel and those from a previous publication on coherent $$\phi$$ production on the deuteron has been carried out to extract the $$\phi-N$$ total cross section, $$\sigma_{\phi N}$$. The extracted $$\phi-N$$ total cross section favors a value above 20 mb. This value is larger than the value extracted using vector-meson dominance models for $$\phi$$ photoproductionmore » on the proton.« less

  5. Steady-state planar ablative flow

    Manheimer, W. M. ; Colombant, D. G. ; Gardner, J. H. - Physics of Fluids (New York)
    Steady-state planar ablative flow in a laser produced plasma is studied. The calculations relate all steady-state fluid quantities to only three parameters, the material, absorbed irradiance, and laser wavelength. Here, the fluid is divided into three regions; the subcritical expanding plasma, the steady-state ablation front, and the accelerated slab. Boundary conditions at the interfaces of these regions are given. If the absorbed irradiance is nonuniform, the nonuniformity in ablation pressure is calculated. Results are compared with experiment and fluid simulation for both uniform and nonuniform illumination.

  6. Validity of the model used to relate the energy distribution and the adsorption isotherm

    Roles, Jeffry ; Guiochon, Georges - Journal of Chromatography
    The reproducibility and accuracy of the determination of the adsorption energy distribution for a probe compound on a solid surface is discussed. This distribution can be calculated from the adsorption isotherm, itself derived from the chromatographic profiles of high concentration bands, using the elution by characteristic points method. Further, distributions derived from experimental data acquired under different experimental conditions agree well within the limits of the reproducibility of these data. Band profiles calculated from the adsorption energy distribution are also in excellent agreement with those recorded.

  7. A comparative analysis of global energy models

    Allen, Edward L. ; Edmonds, James A. ; Kuenne, Robert E. - Energy Economics
    This study is a comparative analysis of seven leading models concerned with forecasts of worldwide energy demand through 1985. There are wide variations among the models' projections of non-Communist world demands for OPEC petroleum in 1985. This variation is attributed to two broad causes, economic growth and energy utilization rates. The paper concludes that differences in economic growth assumptions were less important than energy utilization rate assumptions in explaining disparities among energy demand forecasts. The heterogeneous modeling methodologies prevent a further disaggregation of causation into more specific components such as level of energy prices, price elasticities, conservation, rates of technologicalmore » advance, demographic changes, and income effects. Differential petroleum demand projections are also analyzed. Variation in energy projections is attributed to economic growth, energy utilization, and interfuel substitution possibilities. The last category proves to be the largest single source of differences. It is also concluded that supply assumptions accounted for almost none of the differences among projections.« less

  8. Fundamental aspects of energy conservation policy

    van Gool, Willem - Energy
    Our major choice in energy conservation is between producing the present mix of materials, commodities, and services more efficiently or decreasing demand for them. The first option is referred to as the ''technological fix,'' the second one as ''change of lifestyle.'' If the first option fails, changes in lifestyle might become mandatory. This paper deals with the technical fix approach. Higher capital investment can lead to a decrease in direct use of energy. Both the cost and the energy involved in these investments are analyzed along a conservation path, and a limited number of constants are used to describe themore » changes along this path. These constants can also be used to feed technological information into macroeconomic analysis. The time scales involved pose the major problem to achieving conservation by means of a technical fix. An increase in the price of energy will lead to higher capital investments in accordance with the economic lifecycles in the different sectors. For applications with a short lifetime, such as in the transport sector, energy conservation will mainly take place through the construction of new equipment. In sectors with long-lifetime investments (e.g., buildings), retrofitting will be important. The major task of governmental policy is to induce conservation before it is economically acceptable or possible.« less
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