1,049,864 research outputs found
Quadrupole moments in chiral material DyFe3(BO3)4 observed by resonant x-ray diffraction
By means of circularly polarized x-ray beam at Dy L3 and Fe K absorption
edges, the chiral structure of the electric quadrupole was investigated for a
single crystal of DyFe3(BO3)4 in which both Dy and Fe ions are arranged in
spiral manners. The integrated intensity of the resonant x- ray diffraction of
space-group forbidden reflections 004 and 005 is interpreted within the
electric dipole transitions from Dy 2p3 to 5d and Fe 1s to 4p, respectively. We
have confirmed that the 2 handedness of the crystal observed at Dy L3 and Fe K
edges is consistent with that observed at Dy M5 edge in the previous study. By
analyzing the azimuth scans of the diffracted intensity, the electronic
quadrupole moments of Dy 5d and Fe 4p are derived. The temperature profiles of
the integrated intensity of 004 at the Dy L3 and the Fe K edges are similar to
those of Dy-O and Fe-O bond lengths, while that at the Dy M5 edge does not. The
results indicate that the helix chiral orientations of quadrupole moments due
to Dy 5d and Fe 4p electrons are more strongly affected by the crystal fields
than Dy 4f
Commensurate Dy magnetic ordering associated with incommensurate lattice distortion in orthorhombic DyMnO3
Synchrotron x-ray diffraction and resonant magnetic scattering experiments on
single crystal DyMnO3 have been carried out between 4 and 40 K. Below TN(Dy) =
5K, the Dy magnetic moments order in a commensurate structure with propagation
vector 0.5 b*. Simultaneous with the Dy magnetic ordering, an incommensurate
lattice modulation with propagation vector 0.905 b* evolves while the original
Mn induced modulation is suppressed and shifts from 0.78 b* to 0.81 b*. This
points to a strong interference of Mn and Dy induced structural distortions in
DyMnO3 besides a magnetic coupling between the Mn and Dy magnetic moments.Comment: submitted to Phys. Rev. B Rapid Communication
Universal R-matrix Of The Super Yangian Double DY(gl(1|1))
Based on Drinfeld realization of super Yangian Double DY(gl(1|1)), its
pairing relations and universal R-matrix are given. By taking evaluation
representation of universal R-matrix, another realization of
DY(gl(1|1)) is obtained. These two realizations of DY(gl(1|1)) are related by
the supersymmetric extension of Ding-Frenkel map.Comment: 6 pages, latex, no figure
Nuclear effects in the Drell-Yan process at very high energies
We study Drell-Yan (DY) dilepton production in proton(deuterium)-nucleus and
in nucleus-nucleus collisions within the light-cone color dipole formalism.
This approach is especially suitable for predicting nuclear effects in the DY
cross section for heavy ion collisions, as it provides the impact parameter
dependence of nuclear shadowing and transverse momentum broadening, quantities
that are not available from the standard parton model. For p(D)+A collisions we
calculate nuclear shadowing and investigate nuclear modification of the DY
transverse momentum distribution at RHIC and LHC for kinematics corresponding
to coherence length much longer than the nuclear size. Calculations are
performed separately for transversely and longitudinally polarized DY photons,
and predictions are presented for the dilepton angular distribution.
Furthermore, we calculate nuclear broadening of the mean transverse momentum
squared of DY dileptons as function of the nuclear mass number and energy. We
also predict nuclear effects for the cross section of the DY process in heavy
ion collisions. We found a substantial nuclear shadowing for valence quarks,
stronger than for the sea.Comment: 46 pages, 18 figures, title changed and some discussion added,
accepted for publication in PR
Fixed target Drell-Yan data and NNLO QCD fits of parton distribution functions
We discuss the influence of fixed target Drell-Yan data on the extraction of
parton distribution functions at next-to-next-to-leading order (NNLO) in QCD.
When used in a parton distribution fit, the Drell-Yan (DY) data constrain sea
quark distributions at large values of Bjorken x. We find that not all
available DY data are useful for improving the precision of parton distribution
functions (PDFs) obtained from a fit to the deep inelastic scattering (DIS)
data. In particular, some inconsistencies between DIS-based parton distribution
functions and DY data for large values of dilepton rapidity are found. However,
by selecting a sample of the DY data that is both representative and consistent
with the DIS data, we are able to perform a combined PDF fit that significantly
improves the precision of non-strange quark distributions at large values of x.
The NNLO QCD corrections to the DY process are crucial for improving the
precision. They reduce the uncertainty of the theoretical prediction, making it
comparable to the experimental uncertainty in DY cross-sections over a broad
range of x.Comment: 12 pages, revte
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