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.     

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.     

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.     

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.     

Laser polarized muonic atoms

Lasers are an important tool in the field of muon physics. A new application of lasers, namely producing polarized muonic atoms, is the subject of a new program at LAMPF. One technique already demonstrated is stopping unpolarized muons in a laser polarized³He target. A more promising idea is to polarize neutral muonic helium by collisions with laser polrized Rb vapor. These methods for producing polarized muonic helium will be useful for measuring the spin dependence of nuclear muon capture and for determining the induced pseudoscalar coupling.     

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.     

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.     

A spin polarized disc

We present a solution to the gravitational field equations in a Riemann-Cartan spacetime. The solution describes a disc of infinite radius and finite thickness. The solution has three forms which depend on the size of the acceleration. The matter content of the disc is a rotating spin fluid with a constant z acceleration and a spin density polarized along the axis of rotation. The fluid has zero axial and tangential pressures. There is a radial pressure. The energy density and pressure are finite within the disc.     

Nondiffracting transversally polarized beam

Generation of a nondiffracting transversally polarized beam by means of transmitting an azimuthally polarized beam through a multibelt spiral phase hologram and then highly focusing by a high-NA lens is presented. A relatively long depth of focus (～4.84λ) of the electric field with only radial and azimuthal components is achieved. The polarization of the wavefront near the focal plane is analyzed in detail by calculating the Stokes polarization parameters. It is found that the polarization is spatially varying and entirely transversally polarized, and the polarization singularity disappears at the beam center, which makes the central bright channel possible.     

Radially polarized hyperbolic-cosine-Gaussian beam

Vector beams have attracted much interest recently. In this paper, focusing properties of the radially polarized hyperbolic-cosine-Gaussian beam are investigated. Simulation results show that the focal depth increases with increasing cosine parameter in the cosine term of the beam, while focal spot decreases simultaneously, namely, superresolution occurs. Focal depth increase velocity is quicker for larger cosine parameter, while the transverse focal spot shrinks more quickly for smaller cosine parameter. In addition, for two-portion concentric piecewise radially polarized hyperbolic-cosine-Gaussian beam with π phase shift in center circle portion, focal pattern evolves considerably with increasing cosine parameter, and the evolution principle differs for different radius of the center circle portion. Focal splitting and novel focal spots may appear. This kind of vector beam can be used in optical storage, optical manipulation, and lithography.     

Quasi-one-dimensional polarized fermi superfluids

We calculate the zero-temperature (T=0) phase diagram of a polarized two-component Fermi gas in an array of weakly coupled parallel one-dimensional (1D) "tubes" produced by a two-dimensional optical lattice. Increasing the lattice strength drives a crossover from three-dimensional (3D) to 1D behavior, stabilizing the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) modulated superfluid phase. We argue that the most promising regime for observing the FFLO phase is in the quasi-1D regime, where the atomic motion is largely 1D but there is weak tunneling in the other directions that stabilizes long-range order. In the FFLO phase, we describe a phase transition where the quasiparticle spectrum changes from gapless near the 3D regime to gapped in quasi-1D.     

WW collisions from polarized electron or proton beams,polarized luminosities and applications

A complete formulation of Vector boson-Vector boson processes ine ⁺ e ^?,pp andep collisions is done including Parity violation and beam polarization effects. Single vector boson (W ^±,Z, ψ) distributions inside leptons, quarks and proton as well as luminosity factors and polarization asymmetry factors are established for all (parity conserving and parity violating) helicity combinations. First applications are given for single particle (Higgs,Z′) production, for vector boson-vector boson scattering and for heavy fermion pair production.     

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.