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.     

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.     

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. Work supported in part by the KBN-Grant 2-P302-143-06     

Calculation of neutron depolarization in a uniaxial ferromagnet

We consider a ferromagnetic system which is divided into domains with magnetization directions perpendicular to the plane of the sheet. This system is traversed by a polarized thermal neutron beam with the direction of the polarization vector perpendicular to the magnetization directions of the domains. On the basis of a few assumptions, we calculate the depolarization as a function of the direction of the neutron beam with respect to the plane of the sheet and in terms of the distribution function of the domain sizes as seen in a direction in the plane of the sheet. The result of this calculation is compared to a computer simulation of the same problem and to an experimental result published earlier.     

Anisotropy of the incommensurate fluctuations in Sr2RuO4: a study with polarized neutrons

The anisotropy of the magnetic incommensurate fluctuations in Sr2RuO4 has been studied by inelastic neutron scattering with polarized neutrons. We find a sizable enhancement of the out-of-plane component by a factor of 2 for intermediate energy transfer, which appears to decrease for higher energies. Our results qualitatively confirm calculations of the spin-orbit coupling, but the experimental anisotropy and its energy dependence are weaker than predicted.     

Spatial spin resonance of polarized neutrons. A tunable slow neutron filter

The present paper is concerned with the physical properties of the phenomenon of spatial spin resonance (SSR) of polarized neutrons and its applications. The SU(2) group provides a mathematical tool for the theoretical discussion of SSR. The experimental work made use of the WWR-M reactor at the Leningrad Nuclear Physics Institute of the USSR Academy of Sciences.The theoretical analysis of SSR is based, in physical terms, on the concept of two distortion scales of the alternating magnetic field in the frame of reference of a moving neutron, playing the principal role in SSR. A period of the alternating magnetic field is adopted as a unit of scale. Large- scale distortions correspond to a region of the resonance spectrum in the vicinity of the principal resonance maximum, whereas small-scale distortions are mapped in zones away from this maximum.An analysis has enabled us to calculate and design resonators with which it is possible to act on specified parts of the resonance spectrum. These modified resonators are provided by the so-called “shaped meander” and “double meander” configuration, which permit the suppression of the subsidiary maxima and the high-order resonance spectrum. Some applications of these resonators are presented as devices for monochromatization of a polarized thermal neutron beam.     

Self-rotation of elliptically polarized light in Doppler-broadened rubidium atoms

We present a theoretical and experimental study of self-rotation of incident elliptically polarized light on a rubidium atomic vapor. We construct density matrix equations, which are then solved numerically, and further averaged over atomic transit times and a Maxwell-Boltzmann velocity distribution. We calculate the rotation angle as a function of detuning for various laser intensities and polarizations. We compare the calculated results with experimental results and find good agreement between them.     

Neutron interferometry in gravitational field with torsion

We consider the possibility of finding experimental evidence of the fifth force with the measurement of a phase shift of neutron beams via an interferometric apparatus and also a possible rotation of the polarization plane of polarized neutron beams when torsion is introduced in a gravitational field.     

Upper limit to magnetism in LaAlO3/SrTiO3 heterostructures

Using polarized neutron reflectometry we measured the neutron spin-dependent reflectivity from four LaAlO(3)/SrTiO(3) superlattices. Our results imply that the upper limit for the magnetization averaged over the lateral dimensions of the sample induced by an 11 T magnetic field at 1.7 K is less than 2 G. SQUID magnetometry of the neutron superlattice samples sporadically finds an enhanced moment, possibly due to experimental artifacts. These observations set important restrictions on theories which imply a strongly enhanced magnetism at the interface between LaAlO(3) and SrTiO(3).     

Spin-spin effect in the Ho total neutron cross section at energies of 0.4 and 1.0 MeV

Measurements of the spin-spin effect, σ_ss in the total cross section for polarized neutrons on polarized ¹⁶⁵Ho are reported at neutron energies of 0.4 and 1.0 MeV. The absence of an observable effect at 1.0 MeV is in contradiction with a recently reported experimental result. The results of an improved theoretical calculation of σ_ss for neutron energies below 8 MeV are presented and used with the new experimental data to obtain the new limit V_ss < 300 keV for the strength of the spin-spin potential.     

Pancharatnam--Berry phase in space-variant polarization-state manipulations with subwavelength gratings

We report the appearance of a geometrical phase in space-variant polarization-state manipulations. This phase is related to the classic Pancharatnam-Berry phase. We show a method with which to calculate it and experimentally demonstrate its effect, using subwavelength metal stripe space-variant gratings. The experiment is based on a unique grating for converting circularly polarized light at a wavelength of 10.6 mum into an azimuthally polarized beam. Our experimental evidence relies on analysis of far-field images of the resultant polarization.     

Neutron lifetime and density of states of fluoropolymers at low temperatures

Present status of the measurements of the neutron lifetime is shortly reviewed. We report the inelastic neutron scattering measurement of the density of vibrational states G(ω) of two fluoropolymers, which are promising coating materials for the storage of ultracold neutrons (UCNs) in closed volumes covered with polymer film. From determined G(ω), we calculate the expected UCN loss coefficients.     

Neutron storage in a magnetic field

The motion of neutrons in magnetic traps is considered for various cases of neutron polarization. The results of implementing such traps in practice and special features of experiments studying magnetic neutron storage are discussed. The problem of neutron losses during injection via magnetic valves can be solved by conjoining a magnetic trap with a converter of cold neutrons into ultracold ones or with a source of ultracold neutrons. Prospects for expanding neutron-storage experiments by invoking a correlation analysis of neutron decay and by using the transport properties of charged particles in a nonuniform magnetic field are analyzed. In such an investigation, the recording of the storage time of neutrons proper can be supplemented with the detection of decay protons and electrons and with a parallel measurement of the asymmetries of proton and electron emission with respect to the magnetic field. A set of relative measurements permits improving the accuracy of an experimental determination of the neutron lifetime and combining this determination with the determination of correlation coefficients. On this basis, it is possible to find directly the ratio of the weak-interaction constants and the constants themselves. The application of the most advanced reactor and accelerator technologies to subcritical electric nuclear devices optimized for generating cold and ultracold neutrons, along with the use of solid deuterium and superfluid helium, creates preconditions for developing a neutron plant and for launching neutron studies at accelerators. Thus, the work that has been done as a development of V.V. Vladimirsky's proposals on magnetic neutron storage is analyzed, and the potential of a further use of ultracold neutrons and magnetic devices for deploying a full-scale precision experiment to study the beta decay of polarized neutrons is demonstrated.     

Matrix analysis of neutron spin-echo

We describe the general action of a neutron spin-turn coil by a rotation matrix, and the nett action of a sequence of spin-turns is then evaluated as the product of the relevant matrices. In the ideal neutron spin-echo configuration, the spin-turn sequence used is shown to have a resultant action described by the unit matrix if there is only elastic scattering, so that an initially polarized beam is transmitted with unchanged polarization. This is spin-echo focussing. Measurement of changes in the final polarization then provides information on the sample dynamics.Spin-echo focussing permits high resolution to be coupled with a broad incident wavelength spread. We calculate in detail the effect of this polychromaticity on the spinturn coils involved, and present experimental confirmation. General spin-echo configurations are then considered. Finally, we take into account the effect of spin-flip scattering from spin-incoherent samples, and show that spin-flip effects may be decoupled from dynamic effects in the analysis of spin-echo intensity.The techniques evolved are relevant to both monochromatic and polychromatic spinecho spectrometry. Emphasis has been placed on practical aspects of establishing correct spin-turn conditions and analysing spectrometer response in terms of relative transmitted intensity.     

Time evolution of Wikipedia network ranking

X-ray circular magnetic dichroism, polarized neutron diffraction, ac susceptibility, and Seebeck effect have been measured for several members of the RCo₂ series (R = Ho, Tm, Er) as a function of temperature and applied magnetic field. The experimental results show robust parimagnetism (a general behaviour along the RCo₂ series with R being a heavy rare earth ion) and two reversal temperatures in some systems, which is an unexpected result. Polarised neutron diffraction show differences between results obtained on single crystals or polycrystalline ingots. We propose an interpretation of parimagnetic RCo₂ as a Griffiths phase of the high temperature, magnetically ordered, amorphous RCo₂ phase.     

The HERMES internal polarized hydrogen and deuterium target

The HERMES experiment at the electron ring of HERA at DESY studies the spin structure of proton and neutron by deep inelastic scattering of polarized electrons off the nucleons of a highly polarized internal gas target. The target makes use of a storage cell to increase the target density. The polarisation of a sample of the atoms in the cell is measured with a Breit-Rabi polarimeter. A relaxation model based on the diffusion equation has been developed, which is used to calculate the corrections which are needed to determine the absolute target polarization using the measured values. This revised version was published online in August 2006 with corrections to the Cover Date.     

Monte Carlo方法计算快中子在样品中多次散射和通量衰减修正因子

本文叙述计算快中子在样品中自吸收通量衰减因子以及(n,γ)和(n,n')反应多次散射修正因子的Monte Carlo方法数学处理过程。