5,953 research outputs found
Latest Results on and at high
Recent progress from Jefferson Lab has significantly improved our
understanding of the nucleon spin structure in the high- region. Results of
a precision measurement of the neutron spin asymmetry, , in the high-
(valence quark) region are discussed. The up and down quark spin distributions
in the nucleon were extracted. was also measured. The results were
used, in combination with existing data, to extract the second moment, .
Preliminary results on and in the high- region have also
become available. Finally, the results of a precision measurement of the
structure function to study higher twist effects will be presented.Comment: 4 pages, 2 figures, to appear in the DIS2005 Proceedings (AIP
Spin Sum Rules at Low
Recent precision spin-structure data from Jefferson Lab have significantly
advanced our knowledge of nucleon structure at low . Results on the
neutron spin sum rules and polarizabilities in the low to intermediate
region are presented. The Burkhardt-Cuttingham Sum Rule was verified within
experimental uncertainties. When comparing with theoretical calculations,
results on spin polarizability show surprising disagreements with Chiral
Perturbation Theory predictions. Preliminary results on first moments at very
low are also presented.Comment: 4 pages, to be published in the Proceedings of the 10th Conference on
Intersections of Nuclear and Particle Physics (CIPANP
The consistency of estimator under fixed design regression model with NQD errors
In this article, basing on NQD samples, we investigate the fixed design
nonparametric regression model, where the errors are pairwise NQD random
errors, with fixed design points, and an unknown function. Nonparametric
weighted estimator will be introduced and its consistency is studied. As
special case, the consistency result for weighted kernel estimators of the
model is obtained. This extends the earlier work on independent random and
dependent random errors to NQD case
Flux-lattice melting in LaOFFeAs: first-principles prediction
We report the theoretical study of the flux-lattice melting in the novel
iron-based superconductor and
. Using the Hypernetted-Chain closure and an
efficient algorithm, we calculate the two-dimensional one-component plasma pair
distribution functions, static structure factors and direct correlation
functions at various temperatures. The Hansen-Verlet freezing criterion is
shown to be valid for vortex-liquid freezing in type-II superconductors.
Flux-lattice meting lines for and
are predicted through the combination of the density
functional theory and the mean-field substrate approach.Comment: 5 pages, 4 figures, to appear in Phys. Rev.
Spin Sum Rules and Polarizabilities
The Gerasimov-Drell-Hearn sum rule and related dispersive integrals connect
real and virtual Compton scattering to inclusive photo- and electroproduction.
Being based on universal principles as causality, unitarity, and gauge
invariance, these relations provide a unique testing ground to study the
internal degrees of freedom that hold a system together. The present
contribution reviews the spin-dependent sum rules and cross sections of the
nucleon. At small momentum transfer, the data sample information on the long
range phenomena (Goldstone bosons and collective resonances), whereas the
primary degrees of freedom (quarks and gluons) become visible at large momentum
transfer (short distance). The rich body of new data covers a wide range of
phenomena from coherent to incoherent processes, and from the generalized spin
polarizabilities on the low-energy side to higher twist effects in deep
inelastic scattering.Comment: 15 pages, 7 figures, Proc. of Spin structure at long distance,
Newport News, Virginia, 200
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