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101.
V. Bernard B. Kubis U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2005,25(3):419-425
We analyze the Fubini-Furlan-Rosetti sum rule in the framework of covariant baryon chiral perturbation theory to leading one-loop
accuracy and including next-to-leading-order polynomial contributions. We discuss the relation between the subtraction constants
in the invariant amplitudes and certain low-energy constants employed in earlier chiral perturbation theory studies of threshold
neutral pion photoproduction off nucleons. In particular, we consider the corrections to the sum rule due to the finite pion
mass and show that below the threshold they agree well with determinations based on fixed-t dispersion relations. We also discuss the energy dependence of the electric dipole amplitude E0+. 相似文献
102.
A. Wrońska V. Hejny C. Wilkin S. Dymov C. Hanhart V. Komarov H. R. Koch A. Kulikov A. Magiera T. Mersmann S. Mikirtytchiants H. Ohm D. Prasuhn R. Schleichert H. J. Stein H. Ströher 《The European Physical Journal A - Hadrons and Nuclei》2005,26(3):421-428
The dd↦4Heη reaction has been investigated near threshold using the ANKE facility at COSY-Jülich. Both total and differential cross-sections
have been measured at two excess energies, Q = 2.6 MeV and 7.7 MeV, with a subthreshold measurement being undertaken at Q = - 2.6 MeV to study the physical background. While consistent with isotropy at the lower energy, the angular distribution
reveals a pronounced anisotropy at the higher one, indicating the presence of higher partial waves. Options for the decomposition
into partial amplitudes and their consequences for the determination of the s-wave ηα scattering length are discussed. 相似文献
103.
《The European Physical Journal A - Hadrons and Nuclei》2005,24(3):445-458
The exclusive ω electroproduction off the proton was studied in a large kinematical domain above the nucleon resonance region and for the highest possible photon virtuality (Q2) with the 5.75 GeV beam at CEBAF and the CLAS spectrometer. Cross-sections were measured up to large values of the four-momentum transfer (- t < 2.7 GeV2) to the proton. The contributions of the interference terms σ{TT} and σ{TL} to the cross-sections, as well as an analysis of the ω spin density matrix, indicate that helicity is not conserved in this process. The t-channel π0 exchange, or more generally the exchange of the associated Regge trajectory, seems to dominate the reaction γ*p↦ωp, even for Q2 as large as 5 GeV2. Contributions of handbag diagrams, related to Generalized Parton Distributions in the nucleon, are therefore difficult to extract for this process. Remarkably, the high-t behaviour of the cross-sections is nearly Q2-independent, which may be interpreted as a coupling of the photon to a point-like object in this kinematical limit. 相似文献
104.
105.
Lucian Badescu 《Proceedings of the American Mathematical Society》2008,136(5):1505-1513
Let be a submanifold of dimension of the complex projective space . We prove results of the following type.i) If is irregular and , then the normal bundle is indecomposable. ii) If is irregular, and , then is not the direct sum of two vector bundles of rank . iii) If , and is decomposable, then the natural restriction map is an isomorphism (and, in particular, if is embedded Segre in , then is indecomposable). iv) Let and , and assume that is a direct sum of line bundles; if assume furthermore that is simply connected and is not divisible in . Then is a complete intersection. These results follow from Theorem 2.1 below together with Le Potier's vanishing theorem. The last statement also uses a criterion of Faltings for complete intersection. In the case when this fact was proved by M. Schneider in 1990 in a completely different way.
106.
We investigate the photovoltaic properties of hybrid organ/c solar cell based on the blend of poly[2-methoxy-5-(2- ethylhexoxy-l,4-phenylenevinylene) (MEH-PPV), C60 and titanium dioxide (TiO2) nanotubes. In comparison of the composite devices with different TiO2:[MEH-PPV +C60] weight ratios of lw$.% (D1-1), 2wt.% (D1-2), 3wt.% (D1-3), 5wt.% (D1-4), 10wt.% (D1-5) and 20wt.% (D1-6), it is found that the device Dl-a exhibits the best performance. The conversion efficiency is improved by a factor of 3 compared with the MEH-PPV:C60 device. 相似文献
107.
We report on theoretical results about the coherent charge transport of short DNA molecules using the transmission approach, as a function of interbase electronic coupling and electrodes. A dinucleotide poly(GC) chain is studied as a generic case, and the transmission coefficient as well as I–V curves are presented. The well-stacked “π -way” is favorable for conveying charge carriers through short sequences, and the current can be reduced in strong electronic coupling regime. Further, the steplike appearance and threshold voltage in I–V curves dramatically depend on the coupling strength. The electrodes are shown to dominate charge transport of single band and may contribute to the threshold voltage, and the enhancement of conductance in low contact coupling regime is possible. 相似文献
108.
《The European Physical Journal A - Hadrons and Nuclei》2007,33(2):147-155
The beam asymmetry, Σ , was measured at ELSA in the reaction
p → ηp using linearly polarised tagged photon beams, produced by coherent bremsstrahlung off a diamond. The crystal was oriented
to provide polarised photons in the energy range E
γ = 800 to 1400MeV with the maximum polarisation of P
γ = 49 % obtained at 1305MeV. Both dominant decay modes of the η into two photons and 3π0 were used to extract the beam asymmetry from the azimuthal modulation of the cross-section. The measurements cover the angular
range Θcm ≃ 50 -150 degrees. Large asymmetries up to 80% are observed, in agreement with a previous measurement. The eta-MAID model
and the Bonn-Gatchina partial wave analysis describe the measurements, but the required partial waves differ significantly. 相似文献
109.
110.
We show that, for a continuous set of entangled four-partite states, the task of maximizing the payoff in the symmetric-strategy four-player quantum Minority game is equivalent to maximizing the violation of a four-particle Bell inequality. We conclude the existence of direct correspondences between (i) the payoff rule and Bell inequalities, and (ii) the strategy and the choice of measured observables in evaluating these Bell inequalities. We also show that such a correspondence is unique to minority-like games. 相似文献