Polarized antiquark flavor asymmetry in Drell–Yan pair production

We investigate the role of the flavor asymmetry of the nucleon's polarized antiquark distributions in Drell–Yan lepton pair production in polarized nucleon–nucleon collisions at HERA (fixed–target) and RHIC energies. It is shown that the large polarized antiquark flavor asymmetry predicted by model calculations in the large– limit (chiral quark–soliton model) has a dramatic effect on the double spin asymmetries in high mass lepton pair production, as well as on the single spin asymmetries in lepton pair production through –bosons at . Received: 31 May 2000 / Revised version: 1 December 2000 / Published online: 5 February 2001     

A phase sensitive optical rotation measurement in a scattered chiral medium using a Zeeman laser

A novel circular polarized optical heterodyne interferometer using a Zeeman laser to measure optical rotation both in nonscattered and scattered chiral medium is proposed. A pair of correlated orthogonal circular polarized light waves of different temporal frequency propagating in the chiral medium at different speed is studied. This results in phase retardation between circular polarized light waves of which the phase difference is proportional to the optical rotation angle of a linear polarized light in a chiral medium. In the mean time, two orthogonal circular polarized light waves can be treated as a circular polarized photon pair that is able to reduce the scattering effect in a scattered chiral medium. Then the optical rotation angle can be measured in the scattering medium. In addition, a common-path configuration with respect to circular polarized light waves immune the background noise. This further improves the sensitivity on optical rotation measurement based on phase difference detection.     

The identity of the EPR A-center and the self-activated luminescence center in ZnS: Cl

Generation and bleaching with polarized light of the EPR signal associated with the zinc vacancy-chlorine donor pair (A-center) in ZnS : Cl are described. Excitation bands at 3550 and 3300Å and bleaching bands at 9000 and 13,000Å are revealed and their polarization properties determined. The close correlation with the polarized luminescence studies of Koda and Shionoya on the ‘self-activated’ luminescence center confirms that the luminescence arises from the zinc vacancy-chlorine pair.     

Electron-Positron Pair Production in an Arbitrary Polarized Ultrastrong Laser Field

Electron-positron pair production in an arbitrary polarized ultrastrong laser field is investigated in the first order perturbation approximation in which the Volkov states are used for convenient calculation of scattering amplitude and cross section. It is found surprisingly that the optimal pair production depends strongly on the polarization. For some cases of field parameters, the optimal field is elliptically polarized or evenly circularly polarized one, rather than the usual linear polarization as indicated by previous works. Some insights into pair generation are given and some interesting unexpected features are also discussed briefly.     

Electron-Positron Pair Production in an Arbitrary Polarized Ultrastrong Laser Field

Electron-positron pair production in an arbitrary polarized ultrastrong laser field is investigated in the first order perturbation approximation in which the Volkov states are used for convenient calculation of scattering amplitude and cross section. It is found surprisingly that the optimal pair production depends strongly on the polarization. For some cases of field parameters, the optimal field is elliptically polarized or evenly circularly polarized one, rather than the usual linear polarization as indicated by previous works. Some insights into pair generation are given and some interesting unexpected features are also discussed briefly.     

Analytical Study of Pair Production Rate from Vacuum in an Elliptic Polarized Field by a Two-Level Transition Technique

Electron-positron pair production rate created from vacuum in the presence of an elliptically polarized laser field is investigated.By applying the technique of two level transition amplitude,a routine for obtaining pair production rate is presented,and approximate analytical expressions are given both for the low frequency strong field regime and the high frequency weak field regime.We found that for an elliptically polarized field,the electron-positron pair production rate decrease when the elliptic eccentricity increase in the high frequency weak field regime,however,in the low frequency strong field regime,there is almost the same electron-positron pair production rate as in the constant electric field case.     

Production of a Higgs Boson and a Heavy Fermion Pair in Polarized e-e+ Collisions (II)

Russian Physics Journal - The production of a Higgs boson H (h; A) and a heavy fermion pair in arbitrarily polarized electron-positron collisions is investigated for the minimal supersymmetric...     

The Breit-Wheeler process in the laser field

The electron-positron pair production in a two-photon collision in the field of a moderately strong circularly polarized laser wave was theoretically investigated. The nonresonant kinematics of the pair production has been studied and the cross section for the Breit-Wheeler process was obtained.     

快速测量扭曲向列相液晶盒盒厚

提出了一种利用圆偏光仪测量扭曲向列相液晶盒盒厚的新方法,即:圆偏光仪组成为两端是一对起偏器和检偏器,中间放置一对四分之一波片.起偏器和检偏器平行或垂直放置,其中一个四分之一波片的快轴和起偏器透光轴成45°,另一个四分之一波片的快轴和起偏器透光轴成－45°.液晶盒样品直接插入到两四分之一波片中间,无需调整方向.不同于旋转液晶盒或偏振片寻找输出光强最大值或最小值的方法,圆偏光仪测量盒厚不需要旋转任何光学元件或液晶盒观测输出光强的变化,只需要观测检偏器在平行和垂直方向的两个强度值,能够实现快速测量,简洁而且有效.     

Production of an H(h; A) Boson and a Heavy Fermion Pair in Polarized e–e+-Collisions (I)

Russian Physics Journal - The process of production of an H (h; A) boson of the Minimal Supersymmetric Standard Model and a heavy fermion pair in arbitrarily polarized $$ {e}^{-}{e}^{+}\to...     

Simple system for evaluating retardation of liquid crystal cells using grating type liquid crystal polarization splitters

We propose a unique optical system for measuring the retardation of birefringent films using a pair of liquid crystal (LC) gratings; that is, the examined birefringent films are inserted between two LC gratings. Because the LC grating functions as a polarization beam splitter for circularly polarized light, the proposed system is optically equivalent to the measurement system using a pair of two circular polarizers. First, the polarization splitting performance of the LC grating is discussed. It is found that a sufficiently high voltage (such that the retardation is less than a half wavelength) has to be applied for the almost pure circularly polarized diffracted light. Next, the measurement of the retardation of a homogeneous LC cell as an examined birefringent film was demonstrated using the proposed method. The proposed method is revealed to have the same measurement performance as that of the conventional method using a pair of linear polarizers and has an advantage that there is no need for the optic axis of the test birefringent specimen to be set at a specific angle.     

Experiment studies on the polarized gamma-rays generation at KEK-ATF

Polarized positrons can be created through electron-positron pair creation from circularly polarized gamma-rays. Laser-Compton scattering is an effcient method to generate circularly polarized gamma-rays. A high finesse 2-mirror optical stacking cavity had been installed on the straight section of the electron storage ring at KEK-ATF. A 1064 nm circularly polarized pulsed laser beam was stacked in the cavity. Polarized gamma-rays with a maximum energy of 28.3 MeV were produced via inverse Compton scattering of the enhanced laser pulse off an electron beam of 1.28 GeV. The number of generated gamma photons per collision was estimated by a photon detector. It was found that the experimental result was in agreement with the simulated value.     

Pair (Bethe) approximation applied to a frustrated Ising model

It is argued that a macroscopic number of spins in a frustrated Ising model are not polarized to +1 or -1 in the low-temperature limit in the pair (Bethe) approximation. It is conjectured that the low-temperature phase of a frustrated Ising model is always paramagnetic in the pair (Bethe) approximation.     

Extinction of polarized light in ferrofluids with different magnetic particle concentrations

The magnetic field intensity and nanoparticle concentration dependence of the polarized light extinction in a ferrofluid made of magnetite particles stabilized with technical grade oleic acid dispersed in transformer oil was experimentally investigated. The magnetically induced optical anisotropy, i.e. the dichroism divided by concentration, was found to decrease with increasing sample concentration from 2% to 8%. The magnetically induced change in the optical extinction of light polarized at 54.74° with respect to the magnetic field direction was found to be positive for the less concentrated sample (2%) and negative for the samples with 4% and 8% magnetic nanoparticle concentrations, the more negative the higher the concentration and field intensity. Based on the theoretically proven fact [11] that the particle orientation mechanism has no effect on the extinction of light polarized at 54.74° with respect to the field direction, we analyzed the experimental findings in the frames of the agglomeration and long-range pair correlations theories for the magnetically induced optical anisotropy in ferrofluids. We developed a theoretical model in the approximation of single scattering for the optical extinction coefficient of a ferrofluid with magnetically induced particle agglomeration. The model predicts the existence of a polarization independent component of the optical extinction coefficient that is experimentally measurable at 54.74° polarization angle. The change in the optical extinction of light polarized at 54.74° is positive if only the formation of straight n-particle chains is considered and may become negative in the hypothesis that the longer chains degenerate to more isotropic structures (polymer-like coils, globules or bundles of chains). The model for the influence on the light absorption of the long-range pair correlations, published elsewhere, predicts that the change in the optical extinction of light polarized at 54.74° is always negative, the more negative the higher the magnetic field intensity and particle concentration.     

Demonstration of a high-field short-period superconducting helical undulator suitable for future TeV-scale linear collider positron sources

The first demonstration of a full-scale working undulator module suitable for future TeV-scale positron-electron linear collider positron sources is presented. Generating sufficient positrons is an important challenge for these colliders, and using polarized e(+) would enhance the machine's capabilities. In an undulator-based source polarized positrons are generated in a metallic target via pair production initiated by circularly polarized photons produced in a helical undulator. We show how the undulator design is developed by considering impedance effects on the electron beam, modeling and constructing short prototypes before the successful fabrication, and testing of a final module.     

Plasmonic metamaterial wave retarders in reflection by orthogonally oriented detuned electrical dipoles

We demonstrate that a pair of perpendicular electrical dipolar scatterers resonating at different frequencies can be used as a metamaterial unit cell to construct a nanometer-thin retarder in reflection, designing nanocross and nanobrick plasmonic configurations to function as reflecting quarter-wave plates at ~1520 and 770 nm, respectively. The design is corroborated experimentally with a monolayer of gold nanobricks, transforming linearly polarized incident radiation into circularly polarized radiation at ~780 nm.     

Retardation-effect-induced plasmon modes in a silica-core gold-shell nanocylinder pair

The retardation-effect-induced plasmon modes in a silica-core gold-shell nanocylinder pair is investigated by the two-dimension finite difference time domain method. We show that for light polarized perpendicular to the axis connecting the pair, the spectrum depends sensitively on the size of nanocylinder pair. As the size increases, several retardation-induced non-dipolar plasmon modes including multipolar modes appear in the spectrum and the resonance wavelength and strength of its plasmon modes can be tuned by changing separation width between the nanocylinder pair. Both extinction spectra as a function of size of the core-shell nanocylinder and near-field intensity associated with the coupling resonance modes are reported.     

Unidirectional transmission realized by two nonparallel gratings made of isotropic media

We realize a unidirectional transmission by cascading two nonparallel gratings (NPGs) made of isotropic, lossless, and linear media. For a pair of orthogonal linear polarizations, one of the gratings is designed as a polarizer, which is a reflector for one polarization and a transmitter for the other; another grating is designed as a polarization converter, which converts most of one polarized incident wave into another polarized transmitted wave. It is demonstrated by numerical calculation that more than 85% of the incident light energy can be transmitted with less than 1% transmission in the opposite direction for linearly polarized light at normal incidence, and the relative bandwidth of the unidirectional transmission is nearly 9%. The maximum transmission contrast ratio between the two directions is 62 dB. Unlike one-way diffraction grating, the transmitted light of the NPGs is collinear with the incident light, but their polarizations are orthogonal.     

Spin correlations in the resonance reactionsāa→ Ψ(Z) → bb

A study is made of the processes of annihilation of an arbitrarily polarized e^–e⁺ pair into a pair of particles of spin 0, 1/2, 1, and 3/2 in the (Z)-resonance region.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 53–59, October, 1978.