22,058 research outputs found
Avalanches at rough surfaces
We describe the surface properties of a simple lattice model of a sandpile
that includes evolving structural disorder. We present a dynamical scaling
hypothesis for generic sandpile automata, and additionally explore the kinetic
roughening of the sandpile surface, indicating its relationship with the
sandpile evolution. Finally, we comment on the surprisingly good agreement
found between this model, and a previous continuum model of sandpile dynamics,
from the viewpoint of critical phenomena.Comment: 8 Pages, 7 Figures (in 15 parts); accepted for publication in
Physical Review
New broad 8Be nuclear resonances
Energies, total and partial widths, and reduced width amplitudes of 8Be
resonances up to an excitation energy of 26 MeV are extracted from a coupled
channel analysis of experimental data. The presence of an extremely broad J^pi
= 2^+ ``intruder'' resonance is confirmed, while a new 1^+ and very broad 4^+
resonance are discovered. A previously known 22 MeV 2^+ resonance is likely
resolved into two resonances. The experimental J^pi T = 3^(+)? resonance at 22
MeV is determined to be 3^-0, and the experimental 1^-? (at 19 MeV) and 4^-?
resonances to be isospin 0.Comment: 16 pages, LaTe
Multi-particle structures in non-sequentially reorganized hard sphere deposits
We have examined extended structures, bridges and arches, in computer
generated, non-sequentially stabilized, hard sphere deposits. The bridges and
arches have well defined distributions of sizes and shapes. The distribution
functions reflect the contraints associated with hard particle packing and the
details of the restructuring process. A subpopulation of string-like bridges
has been identified. Bridges are fundamental microstructural elements in real
granular systems and their sizes and shapes dominate considerations of
structural properties and flow instabilities such as jamming.Comment: 9 pages, 7 figure
An Alternative Parameterization of R-matrix Theory
An alternative parameterization of R-matrix theory is presented which is
mathematically equivalent to the standard approach, but possesses features
which simplify the fitting of experimental data. In particular there are no
level shifts and no boundary-condition constants which allows the positions and
partial widths of an arbitrary number levels to be easily fixed in an analysis.
These alternative parameters can be converted to standard R-matrix parameters
by a straightforward matrix diagonalization procedure. In addition it is
possible to express the collision matrix directly in terms of the alternative
parameters.Comment: 8 pages; accepted for publication in Phys. Rev. C; expanded Sec. IV,
added Sec. VI, added Appendix, corrected typo
Shaking a Box of Sand
We present a simple model of a vibrated box of sand, and discuss its dynamics
in terms of two parameters reflecting static and dynamic disorder respectively.
The fluidised, intermediate and frozen (`glassy') dynamical regimes are
extensively probed by analysing the response of the packing fraction to steady,
as well as cyclic, shaking, and indicators of the onset of a `glass transition'
are analysed. In the `glassy' regime, our model is exactly solvable, and allows
for the qualitative description of ageing phenomena in terms of two
characteristic lengths; predictions are also made about the influence of grain
shape anisotropy on ageing behaviour.Comment: Revised version. To appear in Europhysics Letter
Bridges in three-dimensional granular packings: experiments and simulations
In this letter, we present the first experimental study of bridge structures
in three-dimensional dry granular packings. When bridges are small, they are
predominantly 'linear', and have an exponential size distribution. Larger,
predominantly 'complex' bridges, are confirmed to follow a power-law size
distribution. Our experiments, which use X-ray tomography, are in good
agreement with the simulations presented here, for the distribution of sizes,
end-to-end lengths, base extensions and orientations of predominantly linear
bridges. Quantitative differences between the present experiment and earlier
simulations suggest that packing fraction is an important determinant of bridge
structure.Comment: 6 pages, 7 figures, accepted by EPL (2013
BSAURUS- A Package For Inclusive B-Reconstruction in DELPHI
BSAURUS is a software package for the inclusive reconstruction of B-hadrons
in Z-decay events taken by the DELPHI detector at LEP. The BSAURUS goal is to
reconstruct B-decays, by making use of as many properties of b-jets as
possible, with high efficiency and good purity. This is achieved by exploiting
the capabilities of the DELPHI detector to their extreme, applying wherever
possible physics knowledge about B production and decays and combining
different information sources with modern tools- mainly artificial neural
networks. This note provides a reference of how BSAURUS outputs are formed, how
to access them within the DELPHI framework, and the physics performance one can
expect.Comment: 52 pages, 24 figures, added author Z.
- …