3,089 research outputs found
On a Possibility to Determine the Sign of the Polarized Gluon Distribution
We investigate the possibility to draw conclusions on the sign of the
spin-dependent gluon distribution, , from existing polarized
DIS data. The spin-dependent parton distributions , and are constructed
in the framework of a phenomenological procedure taking into account some
assumptions on signs of valence and sea parton distributions motivated by 't
Hooft's mechanism of quark-quark interaction induced by instantons. The axial
gluon anomaly and data on integral quark contributions to the proton spin,
, and , are also taken into
account. Predictions for the - and -dependencies of the polarized
proton and neutron structure functions, and , are compared to
experimental data. It is shown that the neutron structure function, , is
especially sensitive to the sign of . The results of our
analysis supports the conclusion that this sign should be positive.Comment: 14 pages, latex, 12 figure
Determination of Polarized PDFs from a QCD Analysis of Inclusive and Semi-inclusive Deep Inelastic Scattering Data
A new combined next to leading order QCD analysis of the polarized inclusive
and semi-inclusive deep inelastic lepton-hadron scattering (DIS) data is
presented. In contrast to previous combined analyses, the terms
(kinematic - target mass corrections, and dynamic - higher twist corrections)
in the expression for the nucleon spin structure function are taken into
account. The new COMPASS data are included in the analysis. The impact of the
semi-inclusive data on the polarized parton densities (PDFs) and on the higher
twist corrections is discussed. The new results for the PDFs are compared to
our (Leader, Sidorov, Stamenov) LSS'06 PDFs, obtained from the fit to the
inclusive DIS data alone, and to those obtained from the de Florian, Sassot,
Stratmann, and Vogelsang global analysis.Comment: 11 pages, 8 figures, a version to be published in Phys. Rev.
Anomalous Pressure Dependence of Kadowaki-Woods ratio and Crystal Field Effects in Mixed-valence YbInCu4
The mixed-valence (MV) compound YbInCu4 was investigated by electrical
resistivity and ac specific heat at low temperatures and high pressures. At
atmospheric pressure, its Kadowaki-Woods (KW) ratio, A/\gamma ^2, is 16 times
smaller than the universal value R_{KW}(=1.0 x 10^-5 \mu \Omega cm mol^2 K^2
mJ^-2), but sharply increases to 16.5R_{KW} at 27 kbar. The pressure-induced
change in the KW ratio and deviation from R_{KW} are analyzed in terms of the
change in f-orbital degeneracy N and carrier density n. This analysis is
further supported by a dramatic change in residual resistivity \rho_0 near 25
kbar, where \rho_0 jumps by a factor of 7.Comment: 4pages, 3figure
Super Landau Models on Odd Cosets
We construct d=1 sigma models of the Wess-Zumino type on the SU(n|1)/U(n)
fermionic cosets. Such models can be regarded as a particular supersymmetric
extension (with a target space supersymmetry) of the classical Landau model,
when a charged particle possesses only fermionic coordinates. We consider both
classical and quantum models, and prove the unitarity of the quantum model by
introducing the metric operator on the Hilbert space of the quantum states,
such that all their norms become positive-definite. It is remarkable that the
quantum n=2 model exhibits hidden SU(2|2) symmetry. We also discuss the planar
limit of these models. The Hilbert space in the planar n=2 case is shown to
carry SU(2|2) symmetry which is different from that of the SU(2|1)/U(1) model.Comment: 1 + 33 pages, some typos correcte
Effect of Magnetization Inhomogeneity on Magnetic Microtraps for Atoms
We report on the origin of fragmentation of ultracold atoms observed on a
permanent magnetic film atom chip. A novel technique is used to characterize
small spatial variations of the magnetic field near the film surface using
radio frequency spectroscopy of the trapped atoms. Direct observations indicate
the fragmentation is due to a corrugation of the magnetic potential caused by
long range inhomogeneity in the film magnetization. A model which takes into
account two-dimensional variations of the film magnetization is consistent with
the observations.Comment: 4 pages, 4 figure
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