33,221 research outputs found
Step Bunching with Alternation of Structural Parameters
By taking account of the alternation of structural parameters, we study
bunching of impermeable steps induced by drift of adatoms on a vicinal face of
Si(001). With the alternation of diffusion coefficient, the step bunching
occurs irrespective of the direction of the drift if the step distance is
large. Like the bunching of permeable steps, the type of large terraces is
determined by the drift direction. With step-down drift, step bunches grows
faster than those with step-up drift. The ratio of the growth rates is larger
than the ratio of the diffusion coefficients. Evaporation of adatoms, which
does not cause the step bunching, decreases the difference. If only the
alternation of kinetic coefficient is taken into account, the step bunching
occurs with step-down drift. In an early stage, the initial fluctuation of the
step distance determines the type of large terraces, but in a late stage, the
type of large terraces is opposite to the case of alternating diffusion
coefficient.Comment: 8pages, 16 figure
Strange quark suppression from a simultaneous Monte Carlo analysis of parton distributions and fragmentation functions
We perform the first simultaneous extraction of unpolarized parton
distributions and fragmentation functions from a Monte Carlo analysis of
inclusive and semi-inclusive deep-inelastic scattering, Drell-Yan lepton-pair
production, and single-inclusive annihilation data. We use data
resampling techniques to thoroughly explore the Bayesian posterior distribution
of the extracted functions, and use -means clustering on the parameter
samples to identify the configurations that give the best description across
all reactions. Inclusion of the semi-inclusive data reveals a strong
suppression of the strange quark distribution at parton momentum fractions , in contrast with the ATLAS observation of enhanced strangeness
in and production at the LHC. Our study reveals significant
correlations between the strange quark density and the strange kaon
fragmentation function needed to simultaneously describe semi-inclusive
production data from COMPASS and inclusive spectra in
annihilation from ALEPH and SLD, as well as between the strange and light
antiquark densities in the proton.Comment: 6 pages, 4 figures; version to appear in Phys. Rev.
Neutrino Induced 4He Break-up Reaction -- Application of the Maximum Entropy Method in Calculating Nuclear Strength Function
The maximum entropy method is examined as a new tool for solving the
ill-posed inversion problem involved in the Lorentz integral transformation
(LIT) method. As an example, we apply the method to the spin-dipole strength
function of 4He. We show that the method can be successfully used for inversion
of LIT, provided the LIT function is available with a sufficient accuracy.Comment: 5 pages, 2 figures. Poster presented by TM at the International
Workshop on Neutrino-Nucleus Interaction in the Few-GeV Region (NuInt15),
Novenber 16-21 2015, Osaka, Japa
First-order transition in the itinerant ferromagnet CoSSe
Undoped CoS is an isotropic itinerant ferromagnet with a continuous or
nearly continuous phase transition at K. In the doped
CoSSe system, the Curie temperature is lowered to K, and the transition becomes clearly first order in nature. In particular
we find a discontinuous evolution of the spin dynamics as well as strong time
relaxation in the ferromagnetic Bragg intensity and small angle neutron
scattering in vicinity of the ferromagnetic transition. In the ordered state
the long-wavelength spin excitations were found to be conventional
ferromagnetic spin-waves with negligible spin-wave gap ( meV),
indicating that this system is also an excellent isotropic (soft) ferromagnet.
In a wide temperature range up to , the spin-wave stiffness
follows the prediction of the two-magnon interaction theory, , with meV-\AA. The stiffness,
however, does not collapse as from below. Instead a
quasielastic central peak abruptly develops in the excitation spectrum, quite
similar to results found in the colossal magnetoresistance oxides such as
(La-Ca)MnO.Comment: 8pages, 8figure
Deep-inelastic and quasielastic electron scattering from nuclei
We perform a combined analysis of inclusive electron scattering data from
nuclei in the deep-inelastic and quasielastic scattering regions, using
Monte Carlo analysis methods and the nuclear weak binding approximation to
establish the range over which the data can be described within the same
theoretical framework. Comparison with quasielastic He cross sections from
SLAC and Jefferson Lab suggests that most features of the data
can be reasonably well described in the impulse approximation with finite-
nuclear smearing functions for momentum transfers GeV. For
the DIS region, we analyze the recent He to deuterium cross section ratio
from the Jefferson Lab E03-103 experiment to explore the possible isospin
dependence of the nuclear effects. We discuss the implications of this for the
MARATHON experiment at Jefferson Lab, and outline how a Bayesian analysis of
He, H and deuterium data can robustly determine the free neutron
structure function.Comment: 45 pages, 14 figure
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