Problems with Initial- and Final-State Interactions in Deep-Inelastic Scattering

Although there exists a vast literature devoted to the theory of deep-inelastic scattering, the restrictions imposed on the (electromagnetic or weak) current operator by its commutation relations with the representation operators of the Poincaré group and locality have not been considered. We argue that there is a problem with the current operator, leading to the standard parton-model results, satisfying these restrictions. At the same time, there exist models where the correct commutation relations and locality are satisfied but the initial- and final-state interactions of the struck quark with the remnants of the target cannot be neglected even in the Bjorken limit. Received June 13, 1997; revised January 19, 1998; accepted for publication January 27, 1998     

小横动量半深度非弹性散射的量子色动力学因子化

论证了在小横动量区域内半深度非弹性散射量子色动力学因子化公式. 为完成因子化, 引进了依赖于横动量的部分子分布函数和碎裂函数, 并扣除了软胶子辐射. 在单圈图的情形下, 证明了因子化的成立, 同时论证了在微扰论的任意阶该因子化的正确性.     

Trends in Polarized Lepton Nucleon Scattering

The thoery of scattering between polarized leptons and polarized nucleons is reviewed in a comprehensive and pedagogical way. The polarized structure functions are introduced and their interpretation in the framework of the QCD parton model is discussed, including the gluon contribution. Sum rules ( = relations between moments of the structure functions) are derived and critically considered. They are then contrasted to recent experimental results.     

Nucleon-Nucleon Correlations and Six-Quark-Cluster Effects in Semi-Inclusive Deep-Inelastic Lepton Scattering off Few-Nucleon Systems

Semi-inclusive deep-inelastic Lepton scattering off few-nucleon systems is investigated assuming that virtual-boson absorption occurs on a hadronic cluster, which can be either a two-nucleon correlated pair or a six-quark bag. In both cases the relevance of nuclear effects on forward and backward nucleon emissions is illustrated and the differences expected in the energy distribution of the emitted nucleons are analyzed both at x < 1 and x > 1. Received March 31, 1994; revised August 29, 1994; accepted for publication September 12, 1994     

Nucleon Compton Scattering in the Perturbative Limit

The paper presents results of perturbative calculations for nucleon Compton scattering. The results are given for the real incoming photon and for the virtual incoming photon.     

在电子-质子碰撞中识别瞬子末态方法的蒙特卡罗研究

在e⁺p深度非弹性散射的光子胶子融合过程中有可能出现瞬子. 这是 一类特殊的事件, 称为瞬子参与的深度非弹性散射事件. 本文用蒙特卡罗事件产生器QCDINS讨论了在瞬子参与的深度非弹性散射事件中识别瞬子末态和流喷注的方法. 对各种不同方法作了对比研究. 找到了一种能使重建得到的喷注能量、瞬子能量、瞬子质量与强子化前的取值均比较接近的最佳方法.     

Exotic Baryons from a Heavy Meson and a Nucleon

We study hadronic molecules formed by a heavy meson and a nucleon respecting heavy quark symmetry. It is shown that the tensor force plays a dominant role to yield a strong attraction in this system.     

Inclusive Electron Scattering Response Functions of 3He

Theoretical longitudinal and transverse electron scattering response functions are discussed in the quasi-elastic region for momentum transfers q ?? 500 MeV/c. The response functions are calculated nonrelativistically, however, relativistic corrections to the nucleon one-body charge and current operators are taken into account. The frame dependence of the results is illustrated and it is shown that the so-called active nucleon Breit frame is the most suitable reference frame. In addition we review the results of a two-fragment model, which takes into account the correct relativistic energy of the final hadronic state assuming that a nucleon is knocked out quasi-elastically. New results for the transverse response function are presented at 700?MeV/c ?? q ?? 1 GeV/c.     

A Monte Carlo Study on the Reconstruction Method for Instanton in Deep-Inelastic e+p Scattering

Instantons can induce characteristic events in deep-inelastic e⁺p scattering. Such effects are expected to become sizable in QCD. In the present paper QCD-instanton induced events are modelled by the Monte Carlo generator QCDINS. Different methods to reconstruct the instanton part and the current jet are tried in the boson-gluon fusion events of deep-inelastic e⁺p scattering with instantons as background, using QCDINS Monte Carlo event generator. A comparison among these methods are performed and an optimum method is proposed, which can reconstruct well the energies of current jet and instanton as well as the mass of instanton. The proposed method will be useful in the Monte Carlo study of the physical properties of instanton, and can serve as a reference in the experimental identification of instanton.     

Nucleon structure from lattice QCD

The aim of these lectures will be to provide an introductory overview of the concepts needed to compute hadronic matrix elements on the lattice from which moments of Generalised Parton Distributions (GPDs) are extracted and to highlight the contributions that current lattice calculations are making to this exciting field of research. Interesting related topics that will be covered include recent work on the nucleon electromagnetic form factors and moments of parton distribution functions, including the nucleon's axial coupling constant, g_A, and the average fraction of the nucleon's momentum carried by the quarks, 〈 x_q〉.     

Quasi-Elastic Scattering of 16C from 12C at 47.5 MeV/Nucleon

Differential cross sections for the quasi-elastic scattering of^16 C at 47.5 MeV/nucleon from ^12 C target are measured.Coupled-channels calculations are carried out and the optical potential parameters are obtained by fitting the experimental angular distribution.     

Nucleon distribution amplitudes from lattice QCD

We calculate low moments of the leading-twist and next-to-leading-twist nucleon distribution amplitudes on the lattice using two flavors of clover fermions. The results are presented in the MS[over ] scheme at a scale of 2 GeV and can be immediately applied in phenomenological studies. We find that the deviation of the leading-twist nucleon distribution amplitude from its asymptotic form is less pronounced than sometimes claimed in the literature.     

Dicke-Narrowing Spectroscopy of Doubly Dressed Electromagnetically Induced Transparency and Singly Dressed Four-Wave-Mixing in a Confined Atomic System

Dicke-narrowing effect appears both in doubly dressed electromagnetically induced transparency and singly dressed four-wave-mixing lines due to the contribution of slow atoms resulting from de-excited effects of atom-wall collision and transient behaviour of atoms in a confined system. A robust recipe for high resolution spectroscopy of electromagnetically induced transparency dressed by two fields and four-wave-mixing lines comparable with the cold atoms is achievable in a thin vapour cell in experiments.     

Scattering from a Bounded Plasma

The electromagnetic scattering from a bounded plasma column in a rectangular waveguide is investigated. Using image and boundary value techniques, equations are formulated for reflection, transmission and attenuation coefficients. Numerical results obtained from computations are in good agreement with results obtained using alternative formulations elsewhere.     

Complete Set of Deuteron Analyzing Powers for dp Elastic Scattering at Intermediate Energies and Three Nucleon Forces

With the aim of clarifying roles of the 3NFs in nuclei experimental programs with the polarized deuteron beam at intermediate energies are in progress at RIKEN RI Beam Factory. As the first step, we have measured a complete set of deuteron analyzing powers in deuteron–proton elastic scattering at 250 and 294 MeV/nucleon. The obtained data are compared with the Faddeev calculations based on the modern nucleon–nucleon forces together with the Tucson–Melbourne’99, and UrbanaIX three nucleon forces.     

Nucleon charge radius from QCD sum rules

The proton and neutron electric radii are calculated within QCD using the sum rules method for processes with small momentum transfers. The agreement with experimental values is good for the proton radius and somewhat poorer for the neutron one due to the numerical smallness.     

Nucleon Tensor Charge from the Quark Model

The ndcleon tensor charge is studied in the quark model. It is found that the contributions from valence constituent quarks are δu_q = 1.17 and δu_g = -0.29, while the contributions from valence current quarks are δu_v = 0.89 and δu_v = -0.22 at scale about 1 Ge V.