共查询到20条相似文献,搜索用时 31 毫秒
1.
Particle production in hadron-nucleus collisions at high energies is discussed in the projectile fragmentation region. The predictions of the constituent quark model are analyzed. The contribution of diffractive interactions is explicitly taken into account. Comparison with the recent Fermilab measurements shows good agreement with the quark model and strong effects of diffractive collisions in some of the analyzed reactions. 相似文献
2.
J. Bartels T. Gehrmann M.G. Ryskin 《The European Physical Journal C - Particles and Fields》1999,11(2):325-333
Using a perturbative model for diffractive interactions, we derive an expression for the polarized diffractive structure
function in the high energy limit. This structure function is given by the interference of diffractive amplitudes with polarized and
unpolarized exchanges. For the polarized exchange we consider both two-gluon and quark-antiquark amplitudes. The polarized
diffractive amplitude receives sizable contributions from non-strongly ordered regions in phase space, resulting in a double
logarithmic enhancement at small x. The resummation of these double logarithmic terms is outlined. We also discuss the transition from our perturbative expression
to the nonperturbative region. A first numerical estimate indicates that the perturbative contribution to the spin asymmetry
is substantially larger than the nonperturbative one.
Received: 7 July 1999 / Published online: 14 October 1999 相似文献
3.
J. Bartels J. Ellis H. Kowalski M. Wüsthoff 《The European Physical Journal C - Particles and Fields》1999,7(3):443-458
We propose a simple parametrization for the deep-inelastic diffractive cross section. It contains the contribution of production to both the longitudinal and the transverse diffractive structure functions, and of the production of final states from transverse photons. We start from the hard region and perform a suitable extrapolation into the soft region.
We test our model on the 1994 ZEUS and H1 data, and confront it with the H1 conjecture of a singular gluon distribution.
Received: 30 June 1998 / Revised version: 3 September 1998 / Pulished online: 3 December 1998 相似文献
4.
The diffractive membrane optical imaging system is an important development trend of ultra large aperture and lightweight space camera. However, related investigations on physics-based diffractive imaging degradation characteristics and corresponding image restoration methods are less studied. In this paper, the model of image quality degradation for the diffraction imaging system is first deduced mathematically based on diffraction theory and then the degradation characteristics are analyzed. On this basis, a novel regularization model of image restoration that contains multiple prior constraints is established. After that, the solving approach of the equation with the multi-norm coexistence and multi-regularization parameters (prior’s parameters) is presented. Subsequently, the space-variant PSF image restoration method for large aperture diffractive imaging system is proposed combined with block idea of isoplanatic region. Experimentally, the proposed algorithm demonstrates its capacity to achieve multi-objective improvement including MTF enhancing, dispersion correcting, noise and artifact suppressing as well as image’s detail preserving, and produce satisfactory visual quality. This can provide scientific basis for applications and possesses potential application prospects on future space applications of diffractive membrane imaging technology. 相似文献
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ISR data on two-particle rapidity correlations in the region y1 ≈ y2 can be understood in terms of the multiperipheral fireball model and indicate an energy independent upper limit of the average fireball mass. The diffractive contribution to the fireball production leads to characteristic shapes of long range correlations. Data on long range rapidity correlations may be used to determine the fractions of non-diffractive and diffractive one- and two-fireball production. 相似文献
7.
Data on diffractive photoproduction of isoscalar states appear to be anomalously large in a number of channels. Isoscalar diffractive photoproduction is studied in a model in which the pomeron is approximated by two gluons, and in which gluon intermediate states are allowed in the pomeron-meson interaction. It is shown that the model allows a resolution of the long-standing problem of the small (in vector meson dominance terms) diffractive θ photoproduction cross section. This sets the scale for the calculation, and it is then demonstrated that the model can explain the large isoscalar cross section if it is due primarily to the diffractive photoproduction of a system of gluons. 相似文献
8.
We review the physical content of the two simplest models of reggeon field theory: namely the eikonal and the Schwimmer models.
The AGK cutting rules are used to obtain the inclusive, the inelastic and the diffractive cross sections. The system of non-linear
equations for these cross sections is written down and analytic expressions for its solution are obtained. We derive the rapidity
gap dependence of the differential cross sections for diffractive dissociation in the Schwimmer model and in its eikonalized
extension. The results are interpreted from the partonic viewpoint of the interaction at high energies.
Received: 23 June 2005, Published online: 6 October 2005 相似文献
9.
In this paper a spin-dependent diffractive model is studied for πN and NN elastic scattering. We find non-trivial results for spin correlation parameters which persist at high energies and have very distinct features in the dip region. It is stressed that these parameters provide good tests of pomeron factorization. 相似文献
10.
We discuss the circumstances under which multiple-pomeron exchange amplitudes can become iterative and show how the intermediate states involved in these amplitudes can be related to the states produced in diffractive dissociation. In order to obtain a soluble model, we construct a simple integral equation, which in an iterative way leads to a multi-pomeron exchange series, including contributions of cut mechanisms involving spectator particles. From a particular solution of this equation we are able to illustrate how the longitudinal-momentum distributions of the diffractive intermediate states influence the relative strength of the cuts. Further from a qualative analysis, we show why one might expect the helicity-non-flip vacuum amplitudes to have strong cuts, while all other amplitudes have weak cuts. A number of related points are also discussed. 相似文献
11.
J. Bartels H. Jung M. Wüsthoff 《The European Physical Journal C - Particles and Fields》1999,11(1):111-125
We study the diffractive production of jets with large transverse momenta in the region of large diffractive masses (small ). Cross sections for transverse and longitudinal photons are obtained in the leading log and log approximation, keeping all powers in log . We perform a numerical study and illustrate the angular distribution of the three jets. We also estimate the integrated
diffractive three jet cross section and compare with the dijet cross section obtained before.
Received: 11 March 1999 / Published online: 14 October 1999 相似文献
12.
In this paper, based on Maxwell's equations and boundary continuity condi-tions of electromagnetic fields, we derive rigorous vector coupled-wave equations of two-dimensional diffractive patterns for an arbitrary polarization in the resonance domain, and describe the solution to these equations. We verify this theory with a practical example, and show the effectiveness of this method for the resonance-domain diffractive optics. 相似文献
13.
K. Golec-Biernat M. Wüsthoff 《The European Physical Journal C - Particles and Fields》2001,20(2):313-321
We review diffractive deep inelastic scattering (DIS) in the light of the collinear factorization theorem. This theorem allows
one to define diffractive parton distributions in the leading twist approach. Due to its selective final states, diffractive
DIS offers interesting insight into the form of the diffractive parton distributions which we explore with the help of the
saturation model. We find Regge-like factorization with the correct energy dependence measured at HERA. A remarkable feature
of diffractive DIS is the dominance of the twist-4 contribution for small diffractive masses. We quantify this effect and
make a comparison with the data.
Received: 22 February 2001 / Revised version: 22 March 2001 / Published online: 3 May 2001 相似文献
14.
D S Narayan 《Pramana》1974,2(5):252-258
Topological cross sections for diffractive and nondiffractive components in pp collisions are deduced on the basis of a dynamical
model proposed earlier to explain the multiplicity distribution of charged particles. The model has an important prediction
for the angular and momentum distributions of charged particles in diffractive events. 相似文献
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在工艺上衍射光学元件是通过相位板来实现的,由于其多台阶化产生的不连续性,会对目标光场产生sinc调制,产生高级次衍射斑,损失了15%或者更多能量。通过对设计衍射光学器件的传统的IO迭代算法进行了研究,提出了一种与衍折射相结合的设计方法,在衍射光学器件的部分区域形成一块连续相位区域,减少了相位片台阶化区域的光强和衍射斑的强度。通过逐步变化连续相位对输出光强情况的影响的研究,可以优化相位参数,使入射到输出面的光束保证一定匀滑性的前提下,提高目标光场区域的衍射效率达到90%以上,能够满足均匀照明的要求。 相似文献
17.
Gaetano Assanto Catherine García-Reimbert Antonmaria A. Minzoni Noel F. Smyth Annette L. Worthy 《Physica D: Nonlinear Phenomena》2011,240(14-15):1213-1219
We investigate the interaction of three optical solitary waves propagating with angular momentum in bulk nematic liquid crystals. The resulting cluster of solitary waves, or nematicons, is shown to orbit about its common centre of “mass”. An elongated isosceles triangle configuration is derived, this solution being the equivalent of the Lagrange solution of Newtonian gravitation. This triangle solution is found to be stable owing to diffractive radiation. A modulation theory explains the existence of the triangle solution as due to the non-monotonicity of an effective potential for the interaction of the solitary waves. This modulation theory also gives good agreement with numerical solutions for the trajectories of the nematicons in the three colours. Finally, it is shown that a cut-off in the shed diffractive radiation prevents the break-up of the triangle due to radiative losses. 相似文献
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Single diffractive hadron-nucleus interactions are studied within the framework of the dual parton model. Introducing a diffractive component into the Monte-Carlo event generator DTUNUC we investigate particle production and the dependence of the diffractive cross section on the atomic number of the target nucleus. A comparison of the numerical results with recent experimental data is presented. We furthermore introduce hadronic cross section fluctuations and discuss their influence on diffractive proton-nucleus cross sections. 相似文献
20.
Putkunz CT D'Alfonso AJ Morgan AJ Weyland M Dwyer C Bourgeois L Etheridge J Roberts A Scholten RE Nugent KA Allen LJ 《Physical review letters》2012,108(7):073901
Ptychographic coherent diffractive imaging (CDI) has been extensively applied using both x rays and electrons. The extension to atomic resolution has been elusive. This Letter demonstrates ptychographic electron diffractive imaging at atomic resolution, permitting identification of structure in a boron nitride helical cone at a resolution of order 1 ?, beyond that of comparative Z-contrast images. A scanning transmission electron microscope is used to create a diverging illumination in a defocused Fresnel CDI geometry, providing a robust strategy leading to a unique solution. 相似文献