Photoproduction with polarized photons as a source of polarized gluon jets

We show that, according to QCD, the direct Compton process γq→qg in polarized photoproduction leads to strongly polarized gluon jets. We also show that this process is expected to dominate in the reaction γp→π⁺ + opposite side jet + X. The study of the opposite side jet will give direct evidence for the spin of the gluon.     

Radiative effects in deep inelastic scattering of polarized leptons by polarized nucleons

Low-order electromagnetic corrections to deep inelastic scattering of polarized leptons by polarized nucleons are derived and investigated using a covariant method. Thorough numerical calculations of the corrections to cross sections and to the measured asymmetry are carried out for μp (ep) scattering in the range of lepton energy E = 200–500 GeV (10–16 GeV). The sensitivity of the corrections to the choice of the structure functions is investigated. The electromagnetic corrections to the asymmetry are found to be less than 10% within the greatest part of the kinematical region, but if x ～ 0, y ～ 1 they can reach a few tens of percent. The lowest order neutral current contribution to the asymmetry is obtained within the framework of standard electroweak interaction theory and the quark parton model. It is found this effect may be significant, especially in the kinematical range where electromagnetic corrections are negligible.     

Inclusive semileptonic decays of polarized Λb Baryons into polarized τ-leptons

We employ OPE techniques within HQET to calculate the inclusive semileptonic decays of polarized Λ_b baryons. Lepton mass effects are included which enables us to also discuss rates into polarized τ-leptons. We present explicit results for the longitudinal polarization of the τ in the Λ_b rest frame as well as in the (τ^?, v_τ) c.m. frame. In both the Λ_b rest frame and in the (τ^?, v_τ) c.m. frame we make use of novel calculational techniques which considerably simplify the calculations. The transverse polarization components of the τ are calculated in the (τ^?, v_τ) c.m. frame. We delineate how to measure the full set of 14 polarized and unpolarized structure functions of the decay process by angular correlation measurements. A set of observables are identified that allow one to isolate the contributions of the twoO(1/m _t ²) nonperturbative matrix elementsK _b and ε_b.     

Vector meson production by inelastic scattering of polarized electrons off polarized nucleons

A general analysis of vector meson production by inelastic scattering of polarized electrons (or muons) off polarized nucleons is presented. Cross section and vector meson decay angular distribution are discussed in terms of s-channel helicity amplitudes for natural and unnatural parity exchange. The question of experiments suitable for analyzing the more refined dynamical features of ?⁰-production is discussed in detail. Estimates are given for the effects to be expected from unnatural parity exchange.     

Simulation studies on the polarized positron generation from circularly polarized gamma-rays

Polarized positrons can be generated through the electron-positron pair creation from circularly polarized gamma-rays hitting a conversion target. Laser-Compton scattering is an efficient method to generate circularly polarized gamma-rays. Simulation studies on these two processes have been done with the Monte Carlo codes, CAIN and GEANT4. Using CAIN to simulate the Laser-Compton scattering process, the energy spectrum of the generated polarized photons could be obtained. GEANT4 was used to study the yield, energy spectrum and the mean polarization of the positrons emanating from the conversion target. To increase the yield of the generated positrons, an optimization study on the thickness of conversion target was also performed.     

Lagrangian dynamics of polarized media

The dynamical equations associated with polarized media in equilibrium are derived from a standard action. This approach applies to arbitrary thermodynamical models of the medium and provides a systematical method for the computation of the total energy-stress tensor for the coupled system of matter and fields.Fellow of the Schweizerischer Nationalfonds.     

获得偏振光的方法

介绍了用反射、折射及干涉等方法获得线偏振光、椭圆偏振光和圆偏振光的方法 ,并从原理、实验及生产工艺等方面进行了说明     

Quasi-free scattering of polarized protons

Cross section and analyzing power, energy-sharing spectra have been measured for the ¹⁶O($\text{p}$, 2p) reaction at an incident energy of 200 MeV for twenty-four different pairs of angles of the detected final-state protons. This general survey is intended to test the validity of the distorted wave impulse approximation (DWIA), particularly with respect to the predicted j-dependent analyzing power caused by the distorting optical potentials and nuclear spin-orbit coupling. Although the data in general confirm this j-dependence, agreement in detail between DWIA calculations and the analyzing power data becomes worse as the momentum of the recoiling nucleus increases. Predictably, the cross-section calculations show more sensitivity to the optical-model parameters than do the analyzing powers. Within the present limits imposed by scanty elastic scattering data, there seems to remain a choice between predicted ($\text{p}$, 2p) cross sections which either are unreasonably large or which have the incorrect energy-sharing shapes. More comprehensive elastic scattering and total reaction cross section data are clearly needed.     

Dynamics of two polarized nanoparticles

The intrinsic dynamics of two interacting electric polarized nanorods is theoretically investigated. The relative motion between them caused by electric dipole–dipole interaction is derived based on the generalized Lagrangian formulation. The results show that the relative translation and rotation are nonlinear and closely dependent on the initial configuration of the two nanorods. Furthermore, the general conditions of the initial configuration, which determine the two nanorods to repel or attract each other at the initial time, are obtained. The two-dimensional relative motion of the two nanorods shows that the antiparallel and head-to-tail ordering stable self-assembly are respectively formed in two planar initial configurations. For different three-dimensional initial configurations, the interesting dynamic relative attraction, repulsion, and oscillation with rotation are respectively realized. Finally, the theoretical schemes which realize the relaxing, direct head-to-tail ordering,and direct antiparallel ordering stable self-assembly are presented according to the different modes of the motion of the nanoparticles. Some of our results agree well with the results of experiments and simulations.     

Backscattering of circularly polarized pulses

Using numerical simulations of vector radiative transport, we examine time-resolved backscattering of circularly polarized plane waves normally incident upon a slab containing a random distribution of latex spheres in water. For large spheres the effect of polarization memory occurs a short time after first-order scattering and before depolarization. It is the result of successive near-forward-scattering events that maintain the incident wave's helicity. For moderately large scatterers it exhibits a simple dependence on the anisotropy factor. For larger spheres or those with higher refractive indices, it also depends on complicated angular and polarization characteristics of backscattering given by Mie theory.     

Neutron-nucleus spin-spin interaction studied with polarized neutrons and polarized 59Co nuclei

We measured the spin-spin cross section of polarized ⁵⁹Co for polarized neutrons of 0.39–2.88 MeV in the perpendicular geometry. Comparing our results with existing data we conclude that the spin-spin potential is of the spherical type.     

Classification of polarized deformation quantizations

We give a classification of polarized deformation quantizations (PDQs) on a symplectic manifold with a (complex) polarization.

Also, we establish a formula which relates the characteristic class of a PDQ to its Fedosov class and to the Chern class of the polarization.     

Two-quantum annihilation of polarized positrons

The cross-section for the two-quantum annihilation-in-flight of partially polarized beams of particles, obtained by using the polarization density matrix, is given. The formula includes the special results of L. A. Page [1]. The annihilation of a longitudinally polarized positron with a transversally polarized electron is discussed. Computations are made in a centre-of-mass system with summing over photon polarizations.

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Abbreviated version of a diploma-thesis for the degree graduate physicist.

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The author wishes to express his sincere gratitude to Professor V. Votruba and Dr. L. Valenta for suggesting this work and for many helpful discussions and criticisms.     

Perspectives for polarized antiprotons

Polarized antiprotons would open a new window in hadron physics providing access to a wealth of single and double spin observables in proton-antiproton interactions. The PAX Collaboration aims to perform the first ever measurement of the spin-dependence of the proton-antiproton cross section at the AD ring at CERN. The spin-dependence of the cross section could in principle be exploited by the spin-filtering technique for the production of a polarized antiproton beam. As a preparatory phase to the experimentation at AD, the PAX Collaboration has initiated a series of dedicated studies with protons at the COSY-ring in Juelich (Germany), aimed at the commissioning of the experimental apparatus and confirmation of the predictions for spin-filtering with protons.     

Imaging with polarized neutrons

While polarized neutrons have long proved to be an outstanding tool for the investigation of magnetic structures by scattering, we report on their potential for real space investigations of magnetic fields on a macroscopic scale by neutron imaging. Due to the ability of neutrons to penetrate thick layers of matter and their high sensitivity to magnetic fields owed to their magnetic moment, neutron imaging enables the investigation of magnetic fields even in bulk samples of condensed matter. We demonstrate how neutrons provide images of magnetic fields trapped in or expelled by superconductors or even reveal the path of electric currents due to the corresponding magnetic fields.     

Instrumentation with polarized neutrons

Neutron scattering with polarization analysis is an indispensable tool for the investigation of novel materials exhibiting electronic, magnetic, and orbital degrees of freedom. In addition, polarized neutrons are necessary for neutron spin precession techniques that path the way to obtain extremely high resolution in space and time. Last but not least, polarized neutrons are being used for fundamental studies as well as very recently for neutron imaging. Many years ago, neutron beam lines were simply adapted for polarized beam applications by adding polarizing elements leading usually to unacceptable losses in neutron intensity. Recently, an increasing number of beam lines are designed such that an optimum use of polarized neutrons is facilitated. In addition, marked progress has been obtained in the technology of ³He polarizers and the reflectivity of large-m supermirrors. Therefore, if properly designed, only factors of approximately 2–3 in neutron intensity are lost. It is shown that S-benders provide neutron beams with an almost wavelength independent polarization. Using twin cavities, polarized beams with a homogeneous phase space and P>0.99 can be produced without significantly sacrificing intensity. It is argued that elliptic guides, which are coated with large m polarizing supermirrors, provide the highest flux.