655 research outputs found
Measurement of kinematic and nuclear dependence of R = Ï_L/Ï_T in deep inelastic electron scattering
We report results on a precision measurement of the ratio R=Ï_L/Ï_T in deep inelastic electron-nucleon scattering in the kinematic range 0.2â€xâ€0.5 and 1â€Q^2â€10 (GeV/c)^2. Our results show, for the first time, a clear falloff of R with increasing Q^2. Our R results are in agreement with QCD predictions only when corrections for target mass effects and some additional higher twist effects are included. At small x, the data on R favor structure functions with a large gluon contribution. We also report results on the differences R_A-R_D and the cross section ratio Ï^A/Ï^D between Fe and Au nuclei and the deuteron. Our results for R_A-R_D are consistent with zero for all x, Q^2 indicating that possible contributions to R from nuclear higher twist effects and spin-0 constituents in nuclei are not different from those in nucleons. The ratios Ï^A/Ï^D from all recent experiments, at all x, Q^2 values, are now in agreement
Measurement of the Difference in R=Ï_L/Ï_T and of Ï^A/Ï^D in Deep-Inelastic e-D, e-Fe, and e-Au Scattering
We measured the differences in R=Ï_L/Ï_T and the cross-section ratio ÏA/ÏD in deep-inelastic electron scattering from D, Fe, and Au nuclei in the kinematic range 0.2â€xâ€0.5 and 1â€Q^2â€5 (Gev/c)^2. Our results for R^A-R^D are consistent with zero for all x and Q^2, indicating that possible contributions to R from nuclear higher-twist effects and spin-0 constituents in nuclei are not different from those in nucleons. The European Muon Collaboration effect is reconfirmed, and the low-x data from all recent experiments, at all Q^2, are now in agreement
Epitaxial Co2Cr0.6Fe0.4Al thin films and magnetic tunneling junctions
Epitaxial thin films of the theoretically predicted half metal
Co2Cr0.6Fe0.4Al were deposited by dc magnetron sputtering on different
substrates and buffer layers. The samples were characterized by x-ray and
electron beam diffraction (RHEED) demonstrating the B2 order of the Heusler
compound with only a small partition of disorder on the Co sites. Magnetic
tunneling junctions with Co2Cr0.6Fe0.4Al electrode, AlOx barrier and Co counter
electrode were prepared. From the Julliere model a spin polarisation of
Co2Cr0.6Fe0.4Al of 54% at T=4K is deduced. The relation between the annealing
temperature of the Heusler electrodes and the magnitude of the tunneling
magnetoresistance effect was investigated and the results are discussed in the
framework of morphology and surface order based of in situ STM and RHEED
investigations.Comment: accepted by J. Phys. D: Appl. Phy
y scaling in electron-nucleus scattering
Data on inclusive electron scattering from A = 4, 12, 27, 56, 197 nuclei at large momentum transfer are presented and analyzed in terms of y scaling. We find that the data do scale for y 1), and we study the convergence of the scaling function with the momentum transfer Q^2 and A
Radiative capture of protons by deuterons
The differential cross section for radiative capture of protons by deuterons
is calculated using different realistic NN interactions. We compare our results
with the available experimental data below . Excellent agreement
is found when taking into account meson exchange currents, dipole and
quadrupole contributions, and the full initial state interaction. There is only
a small difference between the magnitudes of the cross sections for the
different potentials considered. The angular distributions, however, are
practically potential independent.Comment: 4 pages (twocolumn), 4 postscript figures included, submitted for
publication, revised versio
Inclusive Scattering of Polarized Electrons on Polarized 3He Effects of Final State Interaction and the Magnetic Form Factor of the Neutron
Effects of final state interaction on asymmetries in inclusive scattering of
polarized electrons on polarized 3He are investigated using consistent 3He
bound state wave function and 3N continuum scattering states. Significant
effects are found, which influence the extraction of the magnetic neutron form
factor from A_T'. The enhancement found experimentally for A_TL' near the 3N
breakup threshold, which could not be explained in calculations carried through
in plane wave impulse approximation up to now, occurs now also in theory if the
full final state interaction is included.Comment: 29 pages, 5 figure
The f_LT Response Function of D(e,e'p)n at Q^2=0.33(GeV/c)^2
The interference response function f_LT (R_LT) of the D(e,e'p)n reaction has
been determined at squared four-momentum transfer Q^2 = 0.33 (GeV/c)^2 and for
missing momenta up to p_miss= 0.29 (GeV/c). The results have been compared to
calculations that reproduce f_LT quite well but overestimate the cross sections
by 10 - 20% for missing momenta between 0.1 (GeV/c) and 0.2 (GeV/c) .Comment: 12 Pages, 10 figure
Structural Evolution of a Composite Middle to Lower Crustal Section: The Sierra de Pie de Palo, Northwest Argentina
The Sierra de Pie de Palo of northwest Argentina preserves middle to lower crustal metamorphic rocks that were penetratively deformed during Ordovician accretion of the Precordillera terrane to the Gondwana margin. New structural, petrologic, and geochronologic data from a 40 km structural transect reveals that the Sierra de Pie de Palo preserves a middle to lower crustal ductile thrust complex consisting of individual structural units and not an intact ophiolite and cover sequence. Top-to-the-west thrusting occurred intermittently on discrete ductile shear zones from âŒ515 to âŒ417 Ma and generally propagated toward the foreland with progressive deformation. Ordovician crustal shortening and peak metamorphic temperatures in the central portion of the Sierra de Pie de Palo were synchronous with retro-arc shortening and magmatic flare-up within the Famatina arc. Accretion of the Precordillera terrane resulted in the end of arc flare-up and the onset of synconvergent extension by âŒ439 Ma. Continued synextensional to postextensional convergence was accommodated along progressively lower grade shear zones following terrane accretion and the establishment of a new plate margin west of the Precordillera terrane. The results support models of Cordilleran orogens that link voluminous arc magmatism to periods of regional shortening. The deformation, metamorphic, and magmatic history within the Sierra de Pie de Palo is consistent with models placing the region adjacent to the Famatina margin in the middle Cambrian and not as basement to the Precordillera terrane
Casimir-Polder force between an atom and a dielectric plate: thermodynamics and experiment
The low-temperature behavior of the Casimir-Polder free energy and entropy
for an atom near a dielectric plate are found on the basis of the Lifshitz
theory. The obtained results are shown to be thermodynamically consistent if
the dc conductivity of the plate material is disregarded. With inclusion of dc
conductivity, both the standard Lifshitz theory (for all dielectrics) and its
generalization taking into account screening effects (for a wide range of
dielectrics) violate the Nernst heat theorem. The inclusion of the screening
effects is also shown to be inconsistent with experimental data of Casimir
force measurements. The physical reasons for this inconsistency are elucidated.Comment: 10 pages, 1 figure; improved discussion; to appear in J. Phys. A:
Math. Theor. (Fast Track Communications
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