743 research outputs found
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For cooperation and assistance in the work reported here, we gratefully acknowledge Dr.
William Burgoyne, State of Alaska Division of Environmental Conservation and Mr. Delon
Brown, USDA, Alaska Crop and Livestock Reporting Service. We especially appreciate the efforts
of numerous pesticide manufacturers, distributors, dealers, and users who took the necessary
time to provide information essential for this compilation. Richard Maxwell, Agricultural Chemicals
Specialist, Cooperative Extension Service, Washington State University, provided difficult to
locate pesticide label information. The editors of Farm Chemicals Handbook, 1980, provided the
list of preferred names as well as information regarding general application of pesticide products.Acknowledgments -- Introduction -- Reference -- Pesticide Use in Alaska, 197
Resonance Production in RHIC Collisions
Results of resonance particle production measured at RHIC in 200 GeV Au+Au collisions are compared to measurements in p+p and d+Au
collisions in order to verify the existence of an extended hardronically
interacting medium. Yield and momentum distributions of resonances maybe
modified during the fireball lifetime due to resonance decay and the subsequent
rescattering of their decay daughters as well as the regeneration of resonances
from their decay products. Modified momentum spectra in heavy ion collisions
may change the nuclear modification factor R. The influence on the
elliptic flow v due to late regeneration of resonances is discussed.Comment: 6 pages, 6 figures, Proceedings of the 22st Winter Workshop on
Nuclear Dynamics, San Diago, California, 12-18 March, 200
Statistical Mechanics of semi-classical colored Objects
A microscopic model of deconfined matter based on color interactions between
semi-classical quarks is studied. A hadronization mechanism is imposed to
examine the properties and the disassembly of a thermalized quark plasma and to
investigate the possible existence of a phase transition from quark matter to
hadron matter.Comment: Submitted to Phys. Lett.
Collisional processes of on-shell and off-shell heavy quarks in vacuum and in the Quark-Gluon-Plasma
We study the heavy quark scattering on partons of the quark gluon plasma
(QGP) being especially interested in the collisional (elastic) scattering
processes of heavy quarks on quarks and gluons. We calculate the different
cross sections for perturbative partons (massless on-shell particles in the
vacuum) and for dynamical quasi-particles (off-shell particles in the QGP
medium as described by the dynamical quasi-particles model "DQPM") using the
leading order Born diagrams. Our results show clearly the effect of a finite
parton mass and width on the perturbative elastic cross sections which depend on temperature , energy density ,
the invariant energy and the scattering angle . Our detailed
comparisons demonstrate that the finite width of the quasi-particles in the
DQPM - which encodes the multiple partonic scattering - has little influence on
the cross section for as well as
scattering except close to thresholds. Thus when studying the dynamics of
energetic heavy quarks in a QGP medium the spectral width of the
degrees-of-freedom may be discarded. We have, furthermore, compared the cross
sections from the DQPM with corresponding results from hard-thermal-loop (HTL)
approaches. The HTL inspired models - essentially fixing the regulators by
elementary vacuum cross sections and decay amplitudes instead of properties of
the QGP at finite temperature - provide quite different results especially
w.r.t. the temperature dependence of the and cross sections (in all
settings). Accordingly, the transport properties of heavy quarks will be very
different as a function of temperature when compared to DQPM results.Comment: 28 pages, 32 figure
Strangeness dynamics and transverse pressure in relativistic nucleus-nucleus collisions
We investigate hadron production as well as transverse hadron spectra from
proton-proton, proton-nucleus and nucleus-nucleus collisions from 2 GeV
to 21.3 TeV within two independent transport approaches (HSD and UrQMD)
that are based on quark, diquark, string and hadronic degrees of freedom. The
comparison to experimental data on transverse mass spectra from , and
C+C (or Si+Si) reactions shows the reliability of the transport models for
light systems. For central Au+Au (Pb+Pb) collisions at bombarding energies
above 5 AGeV, furthermore, the measured transverse mass
spectra have a larger inverse slope parameter than expected from the default
calculations. We investigate various scenarios to explore their potential
effects on the spectra. In particular the initial state Cronin effect
is found to play a substantial role at top SPS and RHIC energies. However, the
maximum in the ratio at 20 to 30 AGeV is missed by ~40% and
the approximately constant slope of the spectra at SPS energies is not
reproduced either. Our systematic analysis suggests that the additional
pressure - as expected from lattice QCD calculations at finite quark chemical
potential and temperature - should be generated by strong
interactions in the early pre-hadronic/partonic phase of central Au+Au (Pb+Pb)
collisions.Comment: 20 pages, 15 figures, Phys. Rev. C, in pres
Directed and elliptic flow in heavy ion collisions from MeV/nucleon to GeV/nucleon
Recent data from the NA49 experiment on directed and elliptic flow for Pb+Pb
reactions at CERN-SPS are compared to calculations with a hadron-string
transport model, the Ultra-relativistic Quantum Molecular Dynamics (UrQMD)
model.
The rapidity and transverse momentum dependence of the directed and elliptic
flow, i.e. and , are investigated. The flow results are compared to
data at three different centrality bins. Generally, a reasonable agreement
between the data and the calculations is found. Furthermore, the energy
excitation functions of and from MeV to GeV are explored within the UrQMD framework and discussed in the
context of the available data. It is found that, in the energy regime below
GeV, the inclusion of nuclear potentials is necessary to
describe the data. Above GeV beam energy, the UrQMD model starts to
underestimate the elliptic flow. Around the same energy the slope of the
rapidity spectra of the proton directed flow develops negative values. This
effect is known as the third flow component ("antiflow") and cannot be
reproduced by the transport model. These differences can possibly be explained
by assuming a phase transition from hadron gas to quark gluon plasma at about
GeV.Comment: 19 pages, minor changes and modified title as published in PR
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