共查询到20条相似文献,搜索用时 0 毫秒
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C.-W. Kao 《Few-Body Systems》2008,44(1-4):107-110
Using heavy-baryon chiral perturbation theory (HBChPT), we study the leading chiral corrections to the complete set of nucleon generalized parton distributions (GPDs). 相似文献
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We consider double parton distributions in the general case in which the virtualities of the interacting partons are different. We elaborate the corresponding evolution equations and their extension to next-to-leading logarithmic accuracy. 相似文献
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We study the perturbative QCD corrections to the heavy-quark structure functions of charged-lepton deep-inelastic scattering and their impact on global fits of parton distributions. We include the logarithmically enhanced terms near threshold due to soft gluon resummation in the QCD corrections at next-to-next-to-leading order. We demonstrate that this approximation is sufficient to describe the available HERA data in most parts of the kinematic region. The threshold-enhanced next-to-next-to-leading order corrections improve the agreement between predictions based on global fits of the parton distribution functions and the HERA collider data even in the small-x region. 相似文献
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An analytic method for the solution of the evolution equation for generalized parton distributions (GPDs) is presented. The small x, xi asymptotics of GPDs are calculated. 相似文献
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We study the evolution behavior of generalized parton distributions at small longitudinal momentum fraction. Particular attention is paid to the ratio of a generalized parton distribution and its forward limit, to the mixing between quarks and gluons, and to the dependence on the squared momentum transfer t. 相似文献
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B. A. van Tiggelen S. Kawka G. L. J. A. Rikken 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(10):1-10
We develop a QED approach to find the contribution of the quantum vacuum to the electromagnetic Abraham force. Semi-classical theories predict diverging contributions from the quantum vacuum. We show that the divergencies disappear by Kramers-Bethe mass-renormalization. The finite remainder is compared to the relativistic corrections to the Abraham force. This work applies an earlier approach [S.?Kawka, B.A. van Tiggelen, Europhys Lett. 89, 11002 (2010)]1, dedicated to the simpler case of a harmonic oscillator, to the Coulomb interaction, which is more realistic in a QED context. 相似文献
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P. Castelo Ferreira J. Dias de Deus 《The European Physical Journal C - Particles and Fields》2008,54(4):539-545
We compute QCD corrections to QED calculations for vacuum polarization in background magnetic fields. Formally, the diagram
for virtual eē loops is identical to the one for virtual qq̄ loops. However, due to confinement, or to the growth of αs as p2 decreases, a direct calculation of the diagram is not allowed. At large p2 we consider the virtual qq̄ diagram, in the intermediate region we discuss the role of the contribution of quark condensates
〈qq̄〉 and at the low-energy limit we consider the π0, as well as charged pion π+π- loops. Although these effects seem to be out of the measurement accuracy of photon–photon laboratory experiments, they may
be relevant for γ-ray burst propagation. In particular, for emissions from the center of the galaxy (8.5 kpc), we show that
mixing between the neutral pseudo-scalar pion π0 and photons renders a deviation from the power-law spectrum in the TeV range. For scalar quark condensates 〈qq̄〉 and virtual
qq̄ loops are relevant only for very high radiation density ∼300 MeV/fm3 and very strong magnetic fields of order ∼1014 T.
PACS 12.20.Ds; 14.40.-n; 12.38.Aw; 14.65.Bt 相似文献
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E. A. Kuraev L. N. Lipatov T. V. Shishkina 《Journal of Experimental and Theoretical Physics》2001,92(2):203-209
We consider radiative corrections to the electron and photon impact factors. The generalized eikonal representation for the e + e ? scattering amplitude at high energies and fixed momentum transfers is violated by nonplanar diagrams. An additional contribution to the two-loop approximation appears from the Bethe-Heitler mechanism of fermion pair production with the identity of the fermions in the final state taken into account. The violation of the generalized eikonal representation is also related to the charge parity conservation in QED. A one-loop correction to the photon impact factor for small virtualities of the exchanged photon is obtained using the known results for the cross section of the e + e ? production during photon-nuclei interactions. 相似文献
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We investigate parton distributions at small x using moments of the Gribov-Lipatov-Altarelli-Parisi (GLAP) evolution equation with respect to x. In this representation the kernel of the GLAP equation contains singularities in the moment variable ω at ω = 0. We show that the importance of these singularities at small x depends on the form of the starting distributions. We examine the range of x in which the GLAP equation is valid. The restrictions on the range of x depend on the form of the starting distributions. We investigate whether the GLAP equation can be used to interpolate data in the HERA region. Results are given for the structure function F2 at small x. A possible method of determining the gluon distribution from F2 is discussed. 相似文献
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M. Vanderhaeghen 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):429-432
We discuss how generalized parton distributions (GPDs) enter in a variety of hard exclusive processes such as deeply virtual Compton scattering (DVCS) and hard meson electroproduction reactions on the nucleon. We show some key observables which are sensitive to the various hadron structure aspects of the GPDs, and discuss their experimental status.Received: 30 September 2002, Published online: 22 October 2003PACS:
13.60.Fz Elastic and Compton scattering - 13.60.Le Meson production - 12.38.Bx Perturbative calculations 相似文献
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An introductory review of generalized parton distributions (GPDs) is given.Received: 1 November 2002, Published online: 15 July 2003PACS:
13.40.Gp Electromagnetic form factors - 13.60.Fz Elastic and Compton scattering - 13.60.Hb Total and inclusive cross-sections (including deep-inelastic processes) 相似文献
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A. Freund 《The European Physical Journal C - Particles and Fields》2003,31(2):203-214
In this paper, I will explain in as simple and intuitive physical terms as possible what generalized parton distributions are, what new information about the structure of hadrons they convey and therefore what picture of the hadron will emerge. To develop this picture, I will use the example of deeply virtual Compton scattering (DVCS) and exclusive meson electroproduction processes. Based on this picture, I will then make some general predictions for these processes.Received: 2 December 2002, Revised: 20 August 2003, Published online: 2 October 2003 相似文献
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The polarized parton distributions of the photon are determined by imposing a VMD valence-like structure at some low resolution scale. Experimental tests at high energyep colliders are studied for inclusive single photon orW-boson production. 相似文献