82,896 research outputs found

    Influence of the Dirac sea on proton electromagnetic knockout

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    We use the relativistic distorted-wave impulse approximation (RDWIA) to study the effects of negative-energy components of Dirac wave functions on the left-right asymmetry for (e,e'p) reactions on 16-O with 0.2 < Q^2 < 0.8 and 12-C with 0.6 < Q^2 < 1.8 (GeV/c)^2. Spinor distortion is more important for the bound state than for the ejectile and the net effect decreases with Q^2. Spinor distortion breaks Godon equivalence and the data favor the CC2 operator with intermediate coupling to the sea. The left-right asymmetry for Q^2 < 1.2 (GeV/c)^2 is described well by RDWIA calcuations, but at Q^2 = 1.8 (GeV/c)^2 the observed variation with missing momentum is flatter than predicted.Comment: 12 pages, 9 figures, to be submitted to PR

    RDWIA analysis of 12C(e,e'p) for Q^2 < 2 (GeV/c)^2

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    We analyze data for 12C(e,e'p) with Q^2 < 2 (GeV/c)^2 using the relativistic distorted-wave impulse approximation (RDWIA) based upon Dirac-Hartree wave functions. The 1p normalization extracted from data for Q^2 > 0.6 (GeV/c)^2 is approximately 0.87, independent of Q^2, which is consistent with the predicted depletion by short-range correlations. The total 1p and 1s strength for E_m < 80 MeV approaches 100% of IPSM, consistent with a continuum contribution for 30 < E_m < 80 MeV of about 12% of IPSM. Similarly, a scale factor of 1.12 brings RDWIA calculations into good agreement with 12C(e,e'p) data for transparency. We also analyzed low Q^2 data from which a recent NDWIA analysis suggested that spectroscopic factors might depend strongly upon the resolution of the probe. We find that momentum distributions for their empirical Woods-Saxon wave functions fit to low Q^2 data for parallel kinematics are too narrow to reproduce data for quasiperpendicular kinematics, especially for larger Q^2, and are partly responsible for reducing fitted normalization factors.Comment: 19 pages, 14 figures, to be submitted to PR

    Atom-atom ionization mechanism in Argon-Xenon mixtures

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    The atom-atom ionization process occurring in high-purity argon-xenon mixtures has been investigated by means of a conventional shock tube employing a microwave probe to monitor the electron-generation rate. All tests were conducted at approximately atmospheric pressure and at temperatures in the range between 5000° and 9000°K, corresponding to a neutral-particle density of 7.0 X 10^(17) cm^(-3). The cross-sectional slope constant for xenon ionized by collision with an argon atom is 1.8 X 10^(-20) cm^2/eV±20%, that is, equal to that for xenon ionized by collision with another xenon atom. The data for the reaction of argon ionizing xenon are consistent with an activation energy of 8.315 eV, that is, of the xenon-xenon, atom-atom ionization process. No data were obtained for xenon ionizing argon. Good correlation was obtained between the cross sections for electron elastic momentum exchange derived from the microwave experiment and those obtained from beam experiments. The argon-xenon ionization cross section implies that, for atom-atom processes in the noble gases at pressures ~ 1 atm and temperatures ~2/3 eV, the ionization cross section is independent of the electronic structure of the projectile atom

    Naturalism in International Adjudication

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    Islam & International Criminal Law: A Brief (In) Compatibility Study

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    This paper explores why that incompatibility between Islam and international criminal law persists and considers recommendations for mitigating that dynamic. Why is this important? Primarily because the Western-influenced international criminal law apparatus and the Muslim world are likely to collide more often in the future. If a war crimes tribunal is established in Afghanistan, or if the trial of Syrian agents for the assassination of Lebanon’s former prime minister goes forward, it is imperative that Islamic societies touched by those processes feel a sense of “buy-in” or participation that is meaningful for them. Otherwise, it becomes the same old story of Western domination over conflicting Muslim interests, and that story only breeds more resentment and even hatred

    Advanced undergraduate RC circuits: An experimentalist's perspective

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    In this paper, an advanced undergraduate RC circuit is studied in two different ways. The circuit is a typical series RC circuit with a time-varying voltage source. The temporal profile of the voltage is an isolated, Gaussian shaped pulse. The voltage across the resistor as a function of time is analysed using two different methods: deriving an analytical expression and an analysis in the Laplace domain. An attempt is made to suggest and address common problems that students may have with understanding such circuits. A qualitative physical interpretation of the circuit operation is developed using Green's function
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