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     

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.     

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.     

Nucleon form factors from a sidewise dispersion relation

The electromagnetic structure of the nucleons is investigated by using sidewise dispersion relations. In this paper we assume that the pion contributes the main part to the electromagnetic form factors of the nucleons. Good agreement with the experimental values is found for the charge and the magnetic radii whereas the theoretical magnetic moment of the proton is too small.     

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〉.     

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.     

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.     

Lepton-Pair Production in a Nucleon Field

The total cross-sections for the photo-nucleon reactions y + p → p + v + v^? and y + n → n + v + v^? are calculated according to Weinberg-Salam theory. The effect of the form factors is taken in the electromagnetic vertex. The dependence of the total cross-sections on the energy of the incident photon is explicitly shown.     

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.     

Scattering from impurities in a crystal

A time independent scattering theory for a particle in a crystal with impurity is given. It is shown that the scattered wave is the solution of a Lippman Schwinger equation, and that the existence of bound states or narrow resonances is related more to the band structure than to the form of the impurity potential.     

Scattering measurements from a dissolving bubble

A laboratory-scale study on acoustic scattering from a single bubble undergoing dissolution in undersaturated fresh water is presented. Several experiments are performed with the acoustic source driven with five-cycle tone bursts, center frequency of 120 kHz, to insonify a single bubble located on axis of the combined beam of the set of transducers. The bubble is placed on a fine nylon thread located in the far field of the transducer set, arranged in bistatic configuration, in a tank filled with undersaturated water. Backscattered waveforms from the bubble target are acquired every few seconds for several hours until the bubble has completely dissolved, and detailed dissolution curves are produced from the acoustic data. The rate of bubble dissolution is calculated using the solution developed by Epstein and Plesset [J. Chem. Phys. 18, 1505-1509 (1950)]. The results of the experiments performed are in agreement with the calculations.