Phenomenological determination of polarized quark distributions in the nucleon

We present a fit to spin asymmetries which gives polarized quark distributions. These functions are closely related to the ones given by the Martin, Roberts and Stirling fit for unpolarized structure functions. The integrals of polarized distributions are discussed and compared with the corresponding quantities obtained from neutron and hyperon??-decay data. We use the combination of proton, neutron and deuteron spin asymmetries in order to determine the coefficients of our polarized quark distributions. Our fit shows that phenomenologically there is no need for taking polarized gluons into account.     

Vortex solitons with inhomogeneous polarization in nonlocal self-focusing nonlinear media

Both azimuthally and radially polarized vortex solitons are investigated to be able to exist in highly nonlocal nonlinear media. We get exactly analytical solutions of azimuthally polarized vortex solitons with only polarization singularities and radially polarized vortex solitons with both phase singularities and polarization singularities. Both azimuthally and radially polarized vortex solitons can exist in nonlocal self-focusing nonlinear media with proper modulation of the beam power and the degree of nonlocality. Contrary to those of radially polarized counterparts in local Kerr media, the topological charge can be any integer. When the topological charge m ≠ 0, both phase singularities and polarization singularities work. When m = 0, the polarization singularities work. Azimuthally polarized vortex solitons with polarization singularities corresponds to the linearly polarized vortex solitons with single charge. Our results show that polarization singularities work the same way as phase singularities in some sense.     

Phenomenological determination of polarized quark distributions in the nucleon

We present a fit to spin asymmetries which gives polarized quark distributions. These functions are closely related to the ones given by the Martin, Roberts and Stirling fit for unpolarized structure functions. The integrals of polarized distributions are discussed and compared with the corresponding quantities obtained from neutron and hyperonβ-decay data. We use the combination of proton, neutron and deuteron spin asymmetries in order to determine the coefficients of our polarized quark distributions. Our fit shows that phenomenologically there is no need for taking polarized gluons into account.     

Cross-section asymmetries in vector-meson electroproduction and in inelastic ep scattering with polarized beam and target

We discuss the cross-section asymmetries for forward diffractive vector meson (ρ⁰) production by inelastic scattering of longitudinally polarized electrons (or muons) on polarized protons. Only for the case when both the beam and the target are polarized can considerable effects be expected. On the basis of the off-diagonal GVDM we give relations between the cross section asymmetries in ep → epρ⁰ (forward direction) and in ep → eX. For a longitudinally polarized target the cross-section asymmetries in ep → epρ⁰ are predicted to be roughly twice as large as in ep → eX.     

Jet production in polarized proton proton scattering

We propose a model of polarized partonic densities based on Regge behaviour, quark counting rules,U(1) _A Goldberger-Treiman relation and positivity constraints. The resulting polarized proton structure function is found to be in agreement with EMC and SLAC data. From this input we compute double helicity asymmetries for 1 and 2 jet inclusive production in polarized proton proton scattering at high energies. We obtain asymmetries of 10–20% at energies \(\sqrt s = 50 - 500\) GeV.     

Measurements of the total cross section differenceΔσ Т innp transmission between 0.86 and 0.94 GeV

We present results of the total cross section differenceΔσ _Т obtained in transmission measurements at the energies 0.86, 0.88, 0.91 and 0.94 GeV. The SATURNE II polarized beam of free neutrons obtained from the break-up of polarized deuterons was transmitted through the polarized Saclay frozen-spin proton target. The beam and target polarizations were oriented in the vertical direction. The present results agree with previous SATURNE measurements and improve the amplitude analysis in the forward direction.     

Observation of polarization switching: D1 line of sodium in a Fabry-Perot

We report observation of the complete polarization switching sequence for a gas of atoms with a J = $\text{1}\text{2}$ to J = $\text{1}\text{2}$ transition, exposed to resonant or near resonant, linearly polarized laser excitation in an optical cavity. The sequence is from linearly polarized cavity output at low input power to predominantly circularly polarized output at intermediate power and back to linearly polarized output at high input power. The switching is abrupt, exhibits hysteresis and, when hyperfine optical pumping effects are minimized, is phenomenologically in accord with predictions from theory.     

Next-to-leading order jet cross sections in polarized hadronic collisions

We present a next-to-leading order computation in QCD of one-jet and two-jet cross sections in polarized hadronic collisions. Our results are obtained in the framework of a general formalism that deals with soft and collinear singularities using the subtraction method. We construct a Monte Carlo programme that generates events at the partonic level. We use this code to give phenomenological predictions for pp collisions at √S = 500 GeV, relevant for the spin physics programme at RHIC. The possibility of using jet data to constrain the poorly known polarized parton densities is examined.     

Many polarized radiative transfer models

This note is an introduction to the reprint of the 1991 JQSRT article “A new polarized atmospheric radiative transfer model” by K.F. Evans and G.L. Stephens. We discuss the significance of the article, how our two plane-parallel polarized radiative transfer codes came about, how our codes have been used, and more recent developments in polarized radiative transfer modeling.     

Measurement of the spin correlationA ookk innp elastic scattering between 0.63 and 1.08 GeV

We present the measurements of the spin correlation parameterA _ookk (np). A longitudinally polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the longitudinally polarized Saclay frozen-spin proton target. Measurements were carried out at SATURNE II, at neutron beam kinetic energies of 0.63, 0.88, 0.98 and 1.08 GeV. The data points cover the angular region from about 40° to 110° CM. The observed angular dependence ofA _ookk (np) at 0.63 GeV agree with the phase shift analysis predictions except at small angles.     

Polarized electron-proton scattering at highQ 2

We show that polarized electron-proton scattering is an excellent tool to measure helicity changing amplitudes. The asymmetry of polarized protons measured with longitudinally polarized electrons determines the ratio of Pauli (F ²) to Dirac (F ¹) form factors. For the leading Fock state the Pauli form factor originates only from helicity changing quarkgluon interactions which are zero for zero quark masses. Therefore at high momentum transfer the ratioF ²/F ¹ depends essentially on the up and down quark masses.     

BEC-BCS crossover, phase transitions and phase separation in polarized resonantly-paired superfluids

We study resonantly-paired s-wave superfluidity in a degenerate gas of two species (hyperfine states labeled by ↑, ↓) of fermionic atoms when the numbers N_↑ and N_↓ of the two species are unequal, i.e., the system is “polarized.” We find that the continuous crossover from the Bose-Einstein condensate (BEC) limit of tightly-bound diatomic molecules to the Bardeen-Cooper-Schrieffer (BCS) limit of weakly correlated Cooper pairs, studied extensively at equal populations, is interrupted by a variety of distinct phenomena under an imposed population difference ΔN ≡ N_↑ − N_↓. Our findings are summarized by a “polarization” (ΔN) versus Feshbach-resonance detuning (δ) zero-temperature phase diagram, which exhibits regions of phase separation, a periodic FFLO superfluid, a polarized normal Fermi gas and a polarized molecular superfluid consisting of a molecular condensate and a fully polarized Fermi gas. We describe numerous experimental signatures of such phases and the transitions between them, in particular focusing on their spatial structure in the inhomogeneous environment of an atomic trap.     

A method to measure neutron polarization using P-even asymmetry of γ-quantum emission in the neutron-nuclear interaction

A new method to measure polarization of cold/thermal neutrons using P-even asymmetry in nuclear reactions induced by polarized neutrons is proposed. A scheme profiting from a large correlation of the neutron spin and the circular ??-quantum polarization in the reaction (n, ??) of polarized neutrons with nuclei is analyzed. This method could be used, for instance, to measure the neutron-beam polarization in experiments with frequently varying configuration. We show that high accuracy and reliability of measurements could be expected.     

Transverse single spin asymmetry measurements at STAR

Transverse single spin asymmetries A _N are expected to be sensitive to par-ton polarization and orbital angular momentum contributions to the nucleon spin. Significantly large A _N has been observed in different collision systems such as semi-inclusive deep inelastic scattering (SIDIS) and polarized proton-proton (pp) collisions, indicating a dominant contribution of partonic interactions in the non-perturbative regime. Therefore it’s critical to measure A _N in various channels of polarized pp collisions in order to complement SIDIS data and to constrain theoretical models. We report STAR asymmetry measurements on mid-rapidity hadron-jet and di-hadron correlations at √s = 200 GeV and forward rapidity inclusive hadron production at √s = 500 GeV polarized pp collisions.     

Hadronic colliders as probes of the proton spin structure

We perform a systematic analysis of different processes with high energy polarized proton beams: jets, direct photon, lepton pairs (Drell-Yan) andWZ production. Different sets of polarized partonic densities are used that fit EMC and SLAC polarized deep inelastic scattering data with variable amount of quark and gluon components of the proton spin. The case of the future Relativistic Heavy Ion Collider (RHIC) used as a polarized collider at a maximum energy of \(\sqrt s = 500\) GeV is analyzed in detail.     

Spin asymmetries for large-pt jet production in two-photon processes

Relying on the hard scattering formalism we estimate cross sections and spin asymmetries for large-p_t jet production from two-photon processes in collisions of electrons and positrons of definite helicity states. We use distribution functions of polarized partons in polarized electrons obtained in a modified leading logarithmic approximation as well as spin-dependent parton cross sections according to lowest-order QCD calculations. Detecting at least one forward or backward hadronic jet, topologies of jets can be observed different from the 2 large p_t production.     

The shape of saturated-absorption polarimetric resonances caused by transitions between degenerate states of the neon atom

We have studied experimentally and theoretically the shapes of spectropolarimetric resonances of a linearly polarized probe wave for the transitions 1s ₅-2p ₂ and 1s ₅-2p ₄ in the neon atom in the presence of a strong counterpropagating circularly polarized wave of the same frequency. Physical processes that lead to a change in the shape of polarimetric resonances under the action of a longitudinal magnetic field have been determined.     

Search of Stop,Sbottom, -Sneutrino,and Stau at an e+e- linear collider with √s = 0.5 – 2 TeV

We discuss pair production and decays of stops, sbottoms, τ -sneutrinos, and staus in e ⁺ e ^?. annihilation in the energy range √s = 500 GeV to 2 TeV. Numerical predictions within the Minimal Supersymmetric Standard Model (MSSM) for cross sections and decay rates are presented. We study the stop discovery potential for √s = 500 GeV and 10 fb .1 integrated luminosity for polarized e ^?. beams. Moreover, we give an estimate of the error of the soft. breaking stop and sbottom parameters that can be obtained by cross section measurements with polarized e ^?. beams.     

η − η′ photoproduction and the axial isoscalar neutral current coupling

We show that coherentη andη′ photoproduction by means of the Primakoff Effect on the proton depends on the strange component of the neutral axial current coupling. We construct polarization asymmetries that are sensitive to this coupling through theγ?Z interference. Theη′ is not a Goldstone boson of a spontaneously broken chiral symmetry, but a phenomenological analysis of theη andη′ production through chiral perturbation theory allows to calculate the observables of interest. The polarized proton or polarized photon asymmetries are predicted to be close to 10^?4 for ?q ²～0.1?0.5 GeV².     

Dynamical complexity of driven two-level systems. I. External driving by a given laser field

We treat the general dynamic behavior of an externally driven two-level atom with underlyingSU(2) symmetry in the context of dynamical-systems theory. The temporal evolution of an atom driven by a circularly polarized bichromatic laser field is shown to be regular by calculating the power spectra and the stroboscopic phase portraits in terms of theSU(2) group parameters. In contrast to that, the atomic dynamics is shown to be irregular (ergodic) in the case of a linearly polarized bichromatic laser field. Exhibiting a rich variety of regular and irregular motion, an externally drivenSU(2) dynamical system cannot be truly chaotic in the sense of sensitivity to the initial conditions.