Radial compression of an antiproton cloud for production of intense antiproton beams

We report here the radial compression of a large number of antiprotons ( approximately 5 x 10(5)) in a strong magnetic field under ultrahigh vacuum conditions by applying a rotating electric field. Compression without any resonant structures was demonstrated for a range of frequencies from the sideband frequency of 200 kHz to more than 1000 kHz. The radial compression achieved is a key technique for synthesizing and manipulating antihydrogen atoms and antiprotonic atoms.     

A search for radially excited charmonium states in experiments with low-energy antiproton beams

A spectrum of radially excited charmonium states is calculated for the model of relativistic spherically symmetric top for decay products. Within the integral formalism, the widths of these states are calculated for hadron resonance decay. Mass and width values obtained are in good agreement with the results of experiments. Six new radially excited charmonium states are predicted above the D-pair generation threshold equal to 3.73 GeV/s; three of them are experimentally confirmed. The possibility of application of antiproton beams with momentum from 1 to 15 GeV/s for charmonium spectroscopy is discussed, especially for masses exceeding the threshold of D-pair generation. The advantage of antiproton beams is that intensive generation of particle-antiparticle pairs is observed during antiproton-proton annihilation. This fact allows spectroscopic investigations to be performed with sufficient statistics and good accuracy. Therefore, masses and widths of scalar and vector charmonium states can be measured with high accuracy. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 66–73, December, 2007.     

Invariant parameters for characterizing nonuniformly partially polarized beams

In terms of the so-called Wigner-Stokes formalism, within the framework of the second-order irradiance moments of the field, new overall parameters are introduced to characterize the polarization structure of nonuniformly partially polarized beams. These parameters are shown to be invariant upon rotation of the transverse Cartesian coordinate axes, which define the electric field components. Moreover, such parameters are also invariant under propagation through general rotationally symmetric ABCD optical systems. The text was submitted by the authors in English.     

Interpreting data from polarized proton beams

The reactions pp → pp and pp → Δ⁺⁺n with polarized beam and/or polarized target are currently under investigation at the Argonne ZGS. We discuss how to interpret various measured quantities in terms of amplitudes whose behavior is familiar (as functions of s, t). For pp total cross sections and elastic scattering, Argonne measurements will yield Im ?₂ (s,t = 0) and the rather complicated combination $\text{2|?}{}_5\text{|}{}^2\text{+}\text{Re}\text{(?}{}_1\text{?}{}_2{}^1\text{? ?}{}_3\text{?}{}_4{}^1\text{)}$, where ?_i (i = 1, … 5) are conventional s-channel helicity amplitudes. The forward direction (t = 0) is of special interest. We find that for both pp → pp and pp → Δ⁺⁺n, polarized beam — polarized target experiments plus the rather general (testable) assumption that amplitudes with the same s-channel helicity flip quantum numbers are proportional, are sufficient to fully determine all non-vanishing amplitudes at t = 0. Numerical estimates of some observables, based on calculations in a specific model, are also given.     

Multiple filamentation of circularly polarized beams

We derive a new system of equations that describes the propagation of circularly polarized laser beams in a Kerr medium. Analysis and simulations of this system show that multiple filamentation is suppressed for circularly polarized beams.     

Matrix treatment for partially polarized, partially coherent beams

A matrix method is outlined for dealing with quasi-monochromatic, partially polarized light when spatial coherence is not necessarily complete and propagation occurs along beams. Both spatial coherence and polarization properties are described by a single 2x2 matrix whose elements have the structure of mutual intensity functions. Through a simple example it is shown that this matrix can account for differences that would not be revealed by a scalar treatment or by a locally defined polarization matrix.     

Properties of circularly polarized vortex beams

The properties of circularly polarized vortex beams in cylindrical polarization bases are studied. A circularly polarized vortex beam is decomposed into radial and azimuthal polarization. With the proper combination of vortex charge and the handedness of the circular polarization, a focal field with an extremely strong longitudinal component as well as a flat-topped profile can be obtained. The cylindrical decomposition also sheds light on the connections between orbital angular momentum and the spin of the light beams.     

Generation of collinearly propagating orthogonally polarized beams

A simple monolithic device for simultaneous generation of collinearly propagating orthogonally polarized light beams of equal intensity is presented. The common cube beam splitter masked by two linear polarizers is used to achieve the purpose. This is experimentally verified through the use of a Stoke's polarimeter. It is also shown experimentally that the same setup behaves as a polarization phase shifting interferometer.     

Laser production of polarized beams and targets

Hyperfine interaction techniques have historically been applied to produce polarized nuclei. The use of optical pumping with tunable lasers is a new hyperfine interaction method which dramatically extends the range of nuclear species which can be polarized, as well as the fluxes and densities which can be achieved and the temperature range in which experiments can be carried out. Lasers are ideally suided for the production of polarized atomic beams, as will be illustrated for the cases of^6,7Li,²³Na and³He. Techniques for polarizing dense atomic vapors will be described with an emphasis on achieving full Doppler coverage by the method of velocity changing collisions. Experiments leading to the production of a⁶Li target for a parity non-conservation study of the nuclear reaction⁶Li(α,γ)¹⁰B will be reviewed and results obtained to date presented.     

Spatial characterization of general partially polarized beams

The spatial characterization of light beams given in terms of intensity moments is extended to partially polarized beams by means of a generalization of the Stokes-Mueller formalism. A simple classification scheme of partially polarized fields is proposed, and laws of propagation through nonpolarizing and polarizing optical systems are provided. Some invariant parameters are also investigated.     

Characterizing polarization properties of radially polarized beams

In the present work two methods of characterizing polarization properties of well-known radially polarized beams are discussed in both theoretical aspect and experimental aspect. A rotating linear polarizer used behind the beam is known to be used to qualitatively characterize the polarization properties of a radially polarized beam. In this paper for the first time we give the mathematic model of this characterization process. The proposed model helps to analyze the known experimental results. On the other hand two global parameters have been previously proved to be used to characterize the linear or circular polarization content of the radially polarized beams. In this paper for the first time we propose the theoretical model of determining the two parameters in experiments. Some experimental results on characterizing the polarization properties of the real radially polarized beam produced by using different approaches are shown.     

Tight focusing of spirally polarized vortex beams

The tight focusing of spirally polarized focused vortex beams is analyzed numerically based on the vectorial Debye theory. The expressions for the electric field and the orbital angular momentum of focused beams are derived. It is shown that the intensity distribution in the focal plane is dependent on the specific spirally polarized state and the coefficient of the spiral polarization function. By presenting the phase contours of the component polarized in the radial direction, it is found that the radii of dislocation lines will increase with the increase of the power of the spirally polarization function. It is reveled that the same orbital angular momentum can be obtained for different spirally polarized state at certain distance along the propagation direction in the focal region. Besides, the orbital angular momentum distributions for different polarized states have fewer crossover points with each other for higher topological charge. The influence of the spirally polarized state on the orbital angular momentum in the focal plane is also studied.     

Natural shaping of the cylindrically polarized beams

We have experimentally and theoretically shown that the circularly polarized beam bearing a singly charged optical vortex propagating through a uniaxial crystal can be split after focusing into the radially and azimuthally polarized beams in the vicinity of the focal area provided that the polarization handedness and the vortex topological charge have opposite signs.     

Overall parameters for the characterization of non-uniformly totally polarized beams

Several overall parameters are introduced to characterize the linear or circular polarization content of a non-uniformly totally polarized beam over the region of its wavefront where the irradiance is significant. These figures of merit are determined from the values of the Stokes parameters. The physical meaning of the proposed parameters is tested by computing some numerical examples, and their measurability is checked by considering non-uniformly totally polarized fields generated after propagation through uniaxial anisotropic materials.     

How to study a gluon jet produced by antiproton—proton colliding beams

We show that at the energies and luminosities soon to be attained with antiproton—proton colliding beams, the cross section for antiquark—quark annihilation, leading to production of a gluon jet in association with a Z⁰ at large angles, is measurable and has a magnitude, energy dependence, and angular dependence which can serve to establish the existence of the gluon and to fix its spin.     

Spirally polarized beams for polarimetry measurements of deterministic and homogeneous samples

The use of spirally polarized beams (SPBs) in polarimetric measurements of homogeneous and deterministic samples is proposed. Since across any transverse plane such beams present all possible linearly polarized states at once, the complete Mueller matrix of deterministic samples can be recovered with a reduced number of measurements and small errors. Furthermore, SPBs present the same polarization pattern across any transverse plane during propagation, and the same happens for the field propagated after the sample, so that both the sample plane and the plane where the polarization of the field is measured can be chosen at will. Experimental results are presented for the particular case of an azimuthally polarized beam and samples consisting of rotated retardation plates and linear polarizers.     

Circular grating coupler for creating focused azimuthally and radially polarized beams

We show a planar optical circuit design that takes light from an input waveguide and creates a focused azimuthally or radially polarized beam emanating from the surface of the substrate. It is implemented in silicon-on-insulator waveguides and does not require any external components to focus the beam. The focal spot size can be subwavelength and is potentially useful for lithography, imaging, optical data storage, optical trapping, optical excitation of molecules, or coupling to optical fibers.