Λ-超子在RHIC的Au+Au碰撞中的整体极化

We present the Λ-hyperon global polarization in Au+Au collisions at s_NN=62GeV and 200GeV measured with the STAR detector at RHIC. The observed Λ-hyperon global polarization is consistent with zero, what is in agreement with recent measurements of Λ global polarization, as well as φ(1020) and K^*0(892) vector mesons spin alignment with respect to the reaction plane. The possible dependence of the global polarization on relative azimuthal angle between the orbital momentum of the system and the hyperon 3-momentum is discussed. The corresponding systematic uncertainty due to detector acceptance is found to be less than 20%.     

Polarization Conversion of Single Photon via Scattering by a Λ System in a Semi-Infinite Waveguide

We theoretically investigate single-photon polarization conversion via scattering by an atom with Λ configuration coupled to a semi-infinite waveguide and discuss the two cases in which the Λ system is non-degenerated and degenerated. By applying the hard-wall boundary condition of the semi-infinite waveguide, it is found that singlephoton polarization conversion can be realized with unit probability for both cases under the ideal condition.Together with the polarization conversion, the frequency conversion of a single photon can also be realized with unit probability in the ideal case if the Λ system is not degenerated.     

Rapidity dependence of global polarization in heavy ion collisions

We use a geometric model for hadron polarization in heavy ion collisions with an emphasis on the rapidity dependence.The model is based on the model of Brodsky,Gunion,and Kuhn,as well as the Bjorken scaling model.We make predictions regarding the rapidity dependence of global Λ polarization in the collision energy range of 7.7-200 GeV by assuming the rapidity dependence of two parameters,κ and <ρτ>. The predictions can be tested by future beam-energy-scan experiments at the Relativistic Heavy Ion Collider of Brookhaven National Lab.     

在200GeV极化质子质子对撞中产生的反Lambda粒子的极化

We study the polarization of produced Λ in s=200GeV polarized proton-proton collision at RHIC/PHENIX, and also the polarization as a function of its rapidity which may be sensitivity to the quark helicity distributions of the proton and to the polarized fragmentation functions of the quark into the baryon. For polarized data collected in 2003 a very clean Λ peak in pπ⁺ invariant mass spectrum in the mid-rapidity(|η|<0.35) is obtained. In this letter, we report the calculation process of P_Λ as extracted from the data.     

-超子在RHIC的Au Au碰撞中的整体极化(英文)

We present the-hyperon global polarization in Au Au collisions at S_(NN)~(1/2)=62GeV and 200GeV measured with the STAR detector at RHIC.The observed(?)-hyperon global polarization is consistent with zero, what is in agreement with recent measurements of A global polarization,as well asφ(1020)and K~(*0)(892)vector mesons spin alignment with respect to the reaction plane.The possible dependence of the global polarization on relative azimuthal angle between the orbital momentum of the system and the hyperon 3-momentum is discussed.The corresponding systematic uncertainty due to detector acceptance is found to be less than 20%.     

Polarization scrambling characteristic analysis based on density of polarization states statistics

We report a new method to deeply analyze the scrambling characteristic of polarization scramblers based on density of polarization states(DPS) statistics that makes it possible to describe the DPS distribution in detail on the whole Poincaré sphere, thus easy to locate accurately the nonuniform areas of defective polarization scramblers, which cannot be realized by existing methods. We have built a polarization scrambling system to demonstrate the advantages of our method compared with others by experiments and suggested effective evaluation indexes whose validity is well confirmed by applying to a commercial scrambler. Our conclusions are valuable for accurately analyzing and diagnosing the performance of any polarization scrambler, and quality evaluation of polarization controllers or other polarization devices.     

Influence of Hyperon on 1S0 Superfluidity of Nucleons in Neutron Star Matter

We investigate the property of ^1S0 superfluidity of neutrons and protons in the neutron star matter. On the basis of the result, we study the effects of hyperons on the ^1S0 pairing gaps of the two species of the particles. The parameter sets we use are for the Hartree approximation of the relativistic σ - ω model and the mean field approximation of the Walecka model, respectively. The predicted domain of superfluidity is very close to other works, whereas differences appear in the predicted value of the maximum gap. It is found that ∑^-, A and ∑^- have some influences, the scales of which depend on hyperon-meson coupling constants we use besides other factors, on the ^1S0 superfluidity of protons in some density range, and do not have influence on superfluidity of neutrons. Other hyperons have no influence on the ^1S0 superfluidity of neutron and proton due to these hyperons appearing after ^1S0 neutron and proton pairs disappear.     

Performance comparison between sampling methods using DOP as feedback signal for higher-order PMD compensator

We numerically analyzed the performance of the two polarization-mode dispersion(PMD)compensation methods of the single degree of polarization(DOP)sampling and DOP ellipsoid sampling methods.The numerical results show that the single DOP sampling method can generate the maximum DOP,and may result in a small overall differential group delay(DGD)or the principal state of polarization(PSP) launching.By the PSP launching,just the first-order PMD is compensated while second-order PMD not. When the DOP ellipsoid sampling method is used the performance is evidently better,because the effect of high-order PMD on PMD compensation is reduced.     

Polarization Changes of Partially Coherent Electromagnetic Vortex Beams Propagating in Turbulent Atmosphere

We investigate the polarization change of partially coherent electromagnetic vortex beams propagating in turbulent atmosphere. It is shown that the polarization of the beams will experience changes, and the changes of the polarization are dependent on the spatial coherence, topological charges of the beams, and the degree of polarization of the source plane and the atmospheric turbulence. The results obtained may have applications in space optical communication.     

Linear polarization characteristics for terrain identification at millimeter wave band

We experimentally research linear polarization characteristics of various terrains at millimeter wave band for image interpretation. We measure and discuss the polarization phenomena, and consider as well the incident angle which also affects terrain radiometric temperature. An economic single-channel radiometer is used in measurements, and changes to the linear polarization are produced by manually rotating its waveguide. We demonstrate that the characteristic in polarization is a decisive advantage of terrain identification in ways beyond that which can be achieved using an intensity radiometer alone.     

Effect of initial-state target polarization on the single ionization of helium by l-keV electron impact

We report new results of triple differential cross sections for the single ionization of helium by 1-KeV electron impact at the ejection energy of 10 eV. Investigations have been made for both the perpendicular plane and the plane perpendicular to the momentum transfer geometries. The present calculation is based on the threewCoulomb wave function. Here we have also incorporated the effect of target polarization in the initial state. A comparison is made between the present calculation with the results of other theoretical methods and a recent experiment [Diirr M, Dimopoulou C, Najjari B, Dorn A, Bartschat K, Bray I, Fursa D V, Chen Z, Madison D H and Ullrich J 2008 Phys. Rev. A 77 032717]. At an impact energy of 1 KeV, the target polarization is found to induce a substantial change of the cross section for the ionization process. We observe that the effect of target polarization plays a dominant role in deciding the shape of triple differential cross sections.     

Polarization and phase control of two-photon absorption in an isotropic molecular system

<正>We theoretically and experimentally study the polarization and phase control of two-photon absorption in an isotropic molecular system.We theoretically show that the two-photon transition probability decreases when the laser polarization changes from linear through elliptical to circular,and the laser polarization does not affect the control efficiency of two-photon transition probability by shaping the spectral phase.These theoretical results are experimentally confirmed in coumarin 480.Furthermore,we propose that the combination of the laser polarization with the spectral phase modulation can further increase the control efficiency of the two-photon absorption.     

The first-principles study of ferroelectric behaviours of PbTiO3/SrTiO3 and BaTiOn/SrTiO3 superlattices

We have performed the first-principles calculation to investigate the origins of ferroelectricities and different po- larization behaviours of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. The density of state （DOS） and electronic charge profiles show that there are strong hybridizations between atoms Ti and O and between atoms Pb and O which play very important roles in producing the ferroelectricities of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. Ow- ing to the decline of internal electric field in SrTiO3 （ST） layer, the tetragonality and polarizations of superlattices decrease with increasing the fraction of SrTiO3 in the superlattices. We find that the polarization of PbTiO3/SrTiO3 is largerthan that of BaTiO3/SrTiO3 at the same ratio of components, because the polarization mismatch between PbTiO3 and SrTiO3 is larger than that between BaTiO3 and SrTiO3. The polarization and tetragonality are en- hanced with respect to those of bulk tetragonal BaTiO3 in the superlattices BaTiO3/SrTiO3, while the polarization and tetragonality are reduced with respect to those of bulk tetragonal PbTiO3 in superlattices PbTiO3/SrTiO3.     

Different operation states of soliton pulses in an erbium-doped fibre ring laser

We report on the experimental observation of soliton pulses in an erbium doped fibre ring laser. The passive mode-locking is achieved using the nonlinear polarization rotation technique. By adjusting the pump power and the intracavity polarization controllers, a normal soliton, a stable 8th harmonic mode-locked pulse and a noise-like pulse have been observed in our laser. The experimental results revealed that the noise-like pulse is not suitable for the optical telecommunication, and in order to obtain the stable harmonic mode-locked soliton, a strong unstable CW laser field is necessary to mediate global soliton interaction. The formation mechanism of the harmonic mode-locked pulse has also been analysed.     

Effect of the mesons σ~＊ and Φ and the variety of U_Σ~（N） on the transition density of hyperon stars

The effect of the mesons σ＊ and Φ and the variety of UΣ（N ）on the transition density of hyperon stars is examined within the framework of relativistic mean field theory for the baryon octet {n,p,Λ,Σ-,Σ0,Σ＋,Ξand Ξ0} system.It is found that,compared with that without considering the mesons σ＊ and Φ,the transition density of hyperon stars decreases,the critical baryon density that hyperons Σ-,Σ0,Σ＋,Ξand Ξ0 appears to decrease too,but for Λ the effect is not obvious.As U Σ（N ）goes up,the critical baryon density of Σ＋,Σ0 and Σincreases,that of Ξ0 decreases and that of Λ and Ξis fixed.In addition,it is found that the variety of UΣ（N ）almost does not influence the transition density.     

The Photon Polarization Parameter of 2H（n, γ）3H reaction with Inclusion of the Electric Quadrupole Contribution

We use effective field theory （EFT） for the calculation of neutron-deuteron radiative capture at very low energies. We present here the use of EFT to calculate a low-energy photo-nuclear observable in three-body systems, the photon polarization parameter and and fore-aft asymmetry at thermal neutron energies up to next-to-next to leading order （N2 LO）, with inclasion of the electric quadrupole contribution. The photon polarization parameter in total is found to be Rc = -0.421±0.003 and is in good agreement with the other modern theoretical calculations based on modern nucleon-nucleon potentials. In comparison with our previous work, a satisfactory agreement with the available experimental data is found by inclusion of the electric quadrupole contribution.     

A systematic study on the binding energy of Λ hypernuclei

We calculate the binding energy per baryon of the Λ hypernuclei systematically, using the relativistic mean field theory (RMF) in a static frame. Some similar properties are found for most of the Λ hypernuclei confirmed by experiments. The data show that a Λ hypernucleus will be more stable if it is made by adding a Λ hyperon to a stable normal nuclear core, or by replacing a neutron by a Λ hyperon to a stable normal nuclear core. According to our calculations, the existence of some new Λ hypernuclei are predicted under the frame of RMF.     

Orientation of azobenzene molecules in polymer films induced by all-optical poling

A model of the alignment of azobenzene molecules in polymer film induced by all-optical poling is proposed and verified by experiment. We found that when the writing beams of frequencies ω and 2ω are both linearly polarized with their polarization directions parallel to each other, azobenzene molecules tend to reorient to the direction perpendicular to the writing beams polarization. At the end of the writing process, more molecules orient to the direction perpendicular to the writing beams polarization than those which orient to the parallel direction. The alignment of molecules parallel or perpendicular to the polarization of the writing beams is characteristic of polarity or no polarity, respectively. The alignment of molecules along the polarization of writing beams results in the second order nonlinearity in the polymer film. According to the model, a new method to improve the optical poling efficiency is put forward.     

The effect of hadronic scatterings on the measurement of vector meson spin alignments in heavy-ion collisions

Spin alignments of vector mesons and hyperons in relativistic heavy-ion collisions have been proposed as signals of global polarization.The STAR experiment first observed the ∧ polarization.Recently,the ALICE collaboration measured the transverse momentum {PT) and the collision centrality dependence of K*,and Φ spin alignments during Pb-Pb collisions at ~(1/2)sNN=2.76 TeV.A large signal is observed in the low pT region of mid-central collisions for K~*,while the signal is much smaller for Φ,and these have not been understood yet.Since vector mesons have different lifetimes and their decay products have different scattering cross sections,they suffer from different hadronic effects.In this paper,we study the effect of hadronic interactions on the spin alignment of K~*,Φ,and p mesons in relativistic heavy-ion collisions with a multi-phase transport model.We find that hadronic scatterings lead to a deviation of the observed spin alignment matrix element p00 away from the true value for p and K*mesons(with a bigger effect on p) while the effect is negligible for the Φ meson.The effect depends on the kinematic acceptance:the observed p00 value is lower than the true value when the pseudorapidity(η) coverage is small,while there is little effect when the η coverage is large.Hence,this study provides valuable information to understand the vector meson spin alignment signals observed during the experiments.     

Tunable photonic crystals based on ferroelectric and ferromagnetic materials by focused ion beam

By making photonic crystals in ferroelectric and ferromagnetic materials,field-provoked tunability of photonic crystals is broadening the interest in new applications of on-chip photonic devices.We report a nano-precise fabrication of various designs of photonic crystals in these non-conventional materials using the focused ion beam milling technique.Standard methods are developed and parameters for different materials are calibrated.Optical responses such as bandgaps and polarization status changing from planar film waveguide system with these patterns have been examined on ferromagnetic materials.