Microscopic calculation of the inclusive electron scattering structure function in 16O

We calculate the charge form factor and the longitudinal structure function for 16O and compare with the available experimental data, up to a momentum transfer of 4 fm(-1). The ground-state correlations are generated using the coupled-cluster [ exp(S)] method, together with the realistic v18 NN interaction and the Urbana IX three-nucleon interaction. Center-of-mass corrections are dealt with by adding a center-of-mass Hamiltonian to the usual internal Hamiltonian, and by means of a many-body expansion for the computation of the observables measured in the center-of-mass system.     

Exact and approximate solutions for the electron nonsinglet structure function in QED

Two exact, valid up to infinite perturbative order, numerical solutions of the Lipatov equation for the nonsinglet electron structure function in the QED are presented. One of them is of the Monte Carlo type and another is based on the numerical inversion of the Mellin transform. They agree numerically to a very high precision (better than 0.05%). Within the leading logarithmic approximation, the exact solution is compared with the perturbative second and third order exponentiated solutions. It is shown that the perturbative second order solution inspired by the Yennie-Frautschi-Suura (exclusive) exponentiation is much closer to the exact solution than the other ones. New compact analytical formula for the third order exponentiated solution is given. It is shown to be in perfect numerical agreement with the infinite order solution of the Monte Carlo and Mellin type.     

Phenomenology of Σ+→pℓ+ℓ− and the structure of the weak non-leptonic Hamiltonian

The problem of the radiative non-leptonic weak baryon decays is reviewed in light of the new experimental findings. With the aim of exploring the structure of the weak non-leptonic Hamiltonian, we present a detailed phenomenological analysis of Σ⁺→p?⁺?^? transitions. Lower and upper limits for rates derivable with standard physics are determined as Γ(Σ⁺→pe ⁺ e ^?)/Σ⁺→pγ)≧7.2×10^?3 and 1/1210? Γ(Σ⁺→pe ⁺ e ⁺)/Γ(Σ⁺→pe ⁺ e ^?)?1/120. From existing data on Σ⁺→pe ⁺ e ^? we obtain limits on the values of the charge radius form factors |c ₁/b ₁|?5;|c ₂/b ₁|? 10, where the magnetic form factor is given by the Σ⁺→dγ, decay asb ₁(0)= 6.9±0.9 MeV. The short distance contribution of the QCD corrected single quarks→dλ transition is shown not to play a dominant role in these decays.     

Assessing the structure and function of single biomolecules with scanning transmission electron and atomic force microscopes

The scanning transmission electron microscope (STEM) and the atomic force microscope (AFM) have provided a wealth of useful information on a wide variety of biological structures. These instruments have in common that they raster-scan a probe over a sample and are able to address single molecules. In the STEM the probe is a focused electron beam that is deflected by the scan-coils. Detectors collecting the scattered electrons provide quantitative information for each sub-nanometer sized sample volume irradiated. These electron scattering data can be reconstituted to images of single macromolecules or can be integrated to provide the mass of the macromolecules. Samples need to be dehydrated for such quantitative STEM imaging. In contrast, the AFM raster-scans a sharp tip over a sample surface submerged in a buffer solution to acquire information on the sample's surface topography at sub-nanometer resolution. Direct observation of function-related structural changes induced by variation of temperature, pH, ionic strength, and applied force provides insight into the structure-function relationship of macromolecules. Further, the AFM allows single molecules to be addressed and quantitatively unfolded using the tip as nano-tweezers. The performance of these two scanning probe approaches is illustrated by several examples including the chaperonin GroEL, bacterial surface layers, protein crystals, and bacterial appendices.     

Effect of formation of a nanocrystalline structure on the electron work function and ion-electron emission of nickel

The effect of deformational nanostructuring on the electron work function for nickel is investigated. The current-voltage characteristic of the gas discharge with nanocrystalline nickel as the cold cathode is measured. It is found that the electron work function is considerably reduced and the ion-electron emission current in the gas discharge increases upon a decrease in the average size of nickel grains to 100 nm. The observed changes in the electron work function and in the ion-electron emission are analyzed.     

Phenomenology of the Pokaranpne experiment

The phenomenology of the Pokaranpne experiment (yield - 12 kiloton oftnt) conducted in a shale-sandstone rock, 107 meters underground, is described with the aid of computations using a one-dimensional spherical symmetric rock mechanics computer code developed by the authors. The calculated values of cavity radius, spall velocity and extent of rock fracturing are in good agreement with the observed values. The principal mechanism for crater formation at Pokaran was spall and the relatively smaller crater dimensions and non-venting of radioactivity gases were due to lower kinetic energy transferred to the shale-sandstone rock.     

Phenomenology of the proton spin

We analyze the various inputs that go into computing the recently measured first moment of the proton spin structure functiong ₁ ^p (x). The basic inputs are the various valence and sea quark polarisations and the gluonic contribution coming through axial anomaly. We show that the quark model predictions for valence quark polarisations, suitably modified to accommodate Bjorken sum rule, are consistent with measured value of moment of the spin structure function.     

Phenomenology of the nucleon-nucleon potential

A local nucleon-nucleon potential expansion is developed in terms of orthogonal projectors. Considering the nucleon-nucleon (NN) potential as a completely phenomenological structure, the expansion provides an opportunity to obtain the NN scattering phase shifts that can be described by applying a restricted set of operators, dependent on angular and spin-isospin degrees of freedom of the interacting nucleons. The results obtained with an approximation for eight basic operators (central, spin-orbit and tensorial) are consistent with experience in the field, and provide directions for further modifications of realistic NN potentials.     

Study of the tail of the electron distribution function

The direct measurements of the tail (high energy part) of the electron distribution function both in the homogeneous and in the stratified positive column of the Ne low pressure discharge are presented.     

Spin effects in the electron structure functions

The electron structure functions are studied in polarized e ⁺ e ^- scattering. The formulae for longitudinally and transversely polarized electrons are presented. The smallness of the electron mass leads to negligible cross-sections and asymmetries in some cases. Positivity constraints on the structure functions and parton densities are constructed and discussed. The cross-section asymmetries at very high energies, where the inclusion of all elecroweak bosons is necessary, are calculated. Numerical examples, using the asymptotic solutions for the parton densities inside the electron, are presented.Received: 23 June 2004, Revised: 26 October 2004, Published online: 17 December 2004PACS: 12.15.Ji, 12.38.QkJ. Szwed: Work supported by the European Commission contract ICA1-CT-2002-70013/INCO Strategic action on training and excellence, 5FP.Unité Mixte de Recherche du CNRS et des Universités de Provence, de la Méditerranée et du Sud Toulon-Var - Laboratoire affilié a la FRUNAM - FR 2291, CNRS-Luminy, Case 907, 13288 Marseille Cedex 9, France.     

On the electron equilibrium distribution function in the kinetic theory of electron cyclotron maser

The problems concerning the specification of electron equilibrium distribution function for the kinetic theory of ECRM are investigated in this paper. After detailed analysis of the published equilibium distribution functions, several conclusion have been achieved.     

On the electron band structure of liquid metals

The electronic structure and the density of states of simple liquid metals is discussed on the basis of a nonlocal and energy-dependent pseudopotential of the Phillips-Kleinman type. As an example we treat lithium. To calculate this pseudopotential we need to know the states and the eigenvalues of the liquid metal ion cores. For these quantities we use: first, the core data of the free atom; second, of the free ion; third, the data we have determined from the measured phonon dispersion curves. The deviations between the band structures, the density of states as calculated with these pseudopotentials and those of free electrons are considerable.     

TMD Phenomenology

The transverse momentum dependent partonic distributions and fragmentation functions should reveal new properties of the three-dimensional structure of nucleons and of the quark hadronization process. Many experimental data are now available and much progress has been made in their phenomenological interpretation. A short summary of the situation is presented.     

Complete reorganization of the mode structure of the wave function of a channeled electron in a crystal with a superlattice

The dynamics of relativistic electrons subjected to planar channeling in distorted crystals is investigated using step-by-step numerical integration of the Schrödinger equation. It is shown that periodic distortion of a planar channel (the formation of a “superlattice”) can cause complete reorganization of the mode structure of the wave function. In the limit of weak perturbations of the crystal lattice, the simulation results are consistent with the analytical results from perturbation theory. The position of each line in the spontaneous emission spectrum in the case of resonant distortions depends on the length of the superlattice period.     

测量电子气体的速度分布函数

利用夫兰克-赫兹实验仪测量了电子气体的速度分布函数,并分析了电子与氩原子碰撞的动力学过程.     

Phenomenology of radions

In this paper I will discuss the phenomenology of radion of the Randall-Sundrum type models. I will consider the radion couplings and its production and decay, in the same time taking into account the mixing of radion with Higgs.     

An explanation of the structure in the dynamic structure factor of an electron liquid

We explain the recently observed interesting structure in the dynamic structure factor S(k, ω) of various metallic systems by considering processes that involve single-particle and multi-particle excitations.