2,399 research outputs found
Non Identical strange particle correlations in Au-Au collisions at 200 GeV from the STAR experiment
Information about the space-time evolution of colliding nuclei can be
extracted correlating particles emitted from nuclear collisions. The high
density of particles produced in the STAR experiment allows the measurement of
non-identical strange particle correlations. Due to the absence of Coulomb
interaction, and systems are more sensitive to
the source size than pairs. Strong interaction potential has been studied
using , and for the first time, pairs. The
experimental correlation functions have been described in the frame of a model
based on the interaction. The first preliminary measurement of -
correlations has been performed, allowing to extract information about
the freeze-out time and the space-time asymmetries in particle emission closely
related to the transverse radial expansion and decay of resonances.Comment: 3 pages, 3 figures, contribution to proceedings of the Second Warsaw
Meeting on Particle Correlations and Resonances in Heavy Ion Collisions,
Warsaw 15-18 Oct 2003, to be published in Nucleonic
Generic typology for irrigation systems operation
Irrigation management / Irrigation systems / Water use efficiency / Canals / Operations / Typology / Water delivery / Water distribution / Water conveyance / Water storage / Irrigation effects / Environmental effects / Gravity flow / Hydraulics / Constraints / Water supply / Networks / Case studies / Sri Lanka
RD-flatness and RD-injectivity
It is proved that every commutative ring whose RD-injective modules are
-RD-injective is the product of a pure semi-simple ring and a finite
ring. A complete characterization of commutative rings for which each artinian
(respectively simple) module is RD-injective, is given. These results can be
obtained by using the properties of RD-flat modules and RD-coflat modules which
are respectively the RD-relativization of flat modules and fp-injective
modules. It is also shown that a commutative ring is perfect if and only if
each RD-flat module is RD-projective.Comment: A new section is added to the version published in Communications in
Algebra where a complete proof of Theorem 3.1 is give
The Laser of the ALICE Time Projection Chamber
The large TPC () of the ALICE detector at the CERN LHC was
commissioned in summer 2006. The first tracks were observed both from the
cosmic ray muons and from the laser rays injected into the TPC. In this article
the basic principles of operating the lasers are presented,
showing the installation and adjustment of the optical system and describing
the control system. To generate the laser tracks, a wide laser beam is split
into several hundred narrow beams by fixed micro-mirrors at stable and known
positions throughout the TPC. In the drift volume, these narrow beams generate
straight tracks at many angles. Here we describe the generation of the first
tracks and compare them with simulations.Comment: QM06 poster proceedings, 6 pages, 4 figure
Proton - Lambda correlations in Au-Au Collisions at GeV from the STAR experiment
The space-time evolution of the source of particles formed in the collision
of nuclei can be studied through particle correlations. The STAR experiment is
dedicated to study ultra-relativistic heavy ions collisions and allows to
measure non-identical strange particle correlations. The source size can be
extracted by studying , ,
and correlation functions. Strong interaction potential has
been studied for these systems using an analytical model. Final State
Interaction (FSI) parameters have been determined and has shown a significant
annihilation process present in and systems
not present in and .Comment: contribution to the 20th Winter Workshop on Nuclear Dynamic
Isochrones and Luminosity Functions for Old White Dwarfs
Using a new grid of models of cooling white dwarfs, we calculate isochrones
and luminosity functions in the Johnson-Kron/Cousins and HST filter sets for
systems containing old white dwarfs. These new models incorporate a non-grey
atmosphere which is necessary to properly describe the effects of molecular
opacity at the cool temperatures of old white dwarfs. The various functions
calculated and extensively tabulated and plotted are meant to be as utilitarian
as possible for observers so all results are listed in quantities that
observers will obtain. The tables and plots developed should eventually prove
critical in interpreting the results of HST's Advanced Camera observations of
the oldest white dwarfs in nearby globular clusters, in understanding the
results of searches for old white dwarfs in the Galactic halo, and in
determining ages for star clusters of all ages using white dwarfs. As a
practical application we demonstrate the use of these results by deriving the
white dwarf cooling age of the old Galactic cluster M67.Comment: 7 pages, 8 tables, accepted for publication in the Astrophysical
Journa
Wind Forced Variability in Eddy Formation, Eddy Shedding, and the Separation of the East Australian Current
The East Australian Current (EAC), like many other subtropical western boundary currents, is believed to be penetrating further poleward in recent decades. Previous observational and model studies have used steady state dynamics to relate changes in the westerly winds to changes in the separation behavior of the EAC. As yet, little work has been undertaken on the impact of forcing variability on the EAC and Tasman Sea circulation. Here using an eddyâpermitting regional ocean model, we present a suite of simulations forced by the same timeâmean fields, but with different atmospheric and remote ocean variability. These eddyâpermitting results demonstrate the nonlinear response of the EAC to variable, nonstationary inhomogeneous forcing. These simulations show an EAC with high intrinsic variability and stochastic eddy shedding. We show that wind stress variability on time scales shorter than 56 days leads to increases in eddy shedding rates and southward eddy propagation, producing an increased transport and southward reach of the mean EAC extension. We adopt an energetics framework that shows the EAC extension changes to be coincident with an increase in offshore, upstream eddy variance (via increased barotropic instability) and increase in subsurface mean kinetic energy along the length of the EAC. The response of EAC separation to regional variable wind stress has important implications for both past and future climate change studies
Particle mass transport in impact electrochemistry
Impact electrochemistry is a set of methods in which individual micro- or nanoscale particles are detected and analyzed at a miniaturized electrode. Quantitative interpretation of the results, in particular the determination of ultralow concentrations, relies heavily on modeling the mass transport of the particles being analyzed. This is particularly subtle since, due to favorable scaling with increasing particle size, migration and convection play a disproportionate role in the transport of such particles compared to that of small molecules. Here we summarize the main governing principles in electrochemically-driven particle transport. We particularly emphasize the difference between particle electrophoresis and small-ion migration, which has led to inaccuracies in the recent literature.</p
Cartan subalgebras in C*-algebras of Hausdorff etale groupoids
The reduced -algebra of the interior of the isotropy in any Hausdorff
\'etale groupoid embeds as a -subalgebra of the reduced
-algebra of . We prove that the set of pure states of with unique
extension is dense, and deduce that any representation of the reduced
-algebra of that is injective on is faithful. We prove that there
is a conditional expectation from the reduced -algebra of onto if
and only if the interior of the isotropy in is closed. Using this, we prove
that when the interior of the isotropy is abelian and closed, is a Cartan
subalgebra. We prove that for a large class of groupoids with abelian
isotropy---including all Deaconu--Renault groupoids associated to discrete
abelian groups--- is a maximal abelian subalgebra. In the specific case of
-graph groupoids, we deduce that is always maximal abelian, but show by
example that it is not always Cartan.Comment: 14 pages. v2: Theorem 3.1 in v1 incorrect (thanks to A. Kumjain for
pointing out the error); v2 shows there is a conditional expectation onto
iff the interior of the isotropy is closed. v3: Material (including some
theorem statements) rearranged and shortened. Lemma~3.5 of v2 removed. This
version published in Integral Equations and Operator Theor
Perfect category-graded algebras
In a perfect category every object has a minimal projective resolution. We
give a criterion for the category of modules over a categorygraded algebra to
be perfect.Comment: A sufficient condition is replaced by a criterion. Several references
added. 17 page
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