198 research outputs found
The Power of Environmental Observatories for Advancing Multidisciplinary Research, Outreach, and Decision Support: The Case of the Minnesota River Basin
An edited version of this paper was published by AGU. Copyright 2019 American Geophysical Union.Observatoryâscale data collection efforts allow unprecedented opportunities for integrative, multidisciplinary investigations in large, complex watersheds, which can affect management decisions and policy. Through the National Science Foundationâfunded REACH (REsilience under Accelerated CHange) project, in collaboration with the Intensively Managed LandscapesâCritical Zone Observatory, we have collected a series of multidisciplinary data sets throughout the Minnesota River Basin in southâcentral Minnesota, USA, a 43,400âkm2 tributary to the Upper Mississippi River. Postglacial incision within the Minnesota River valley created an erosional landscape highly responsive to hydrologic change, allowing for transdisciplinary research into the complex cascade of environmental changes that occur due to hydrology and land use alterations from intensive agricultural management and climate change. Data sets collected include water chemistry and biogeochemical data, geochemical fingerprinting of major sediment sources, highâresolution monitoring of river bluff erosion, and repeat channel crossâsectional and bathymetry data following major floods. The data collection efforts led to development of a series of integrative reduced complexity models that provide deeper insight into how water, sediment, and nutrients route and transform through a large channel network and respond to change. These models represent the culmination of efforts to integrate interdisciplinary data sets and science to gain new insights into watershedâscale processes in order to advance management and decision making. The purpose of this paper is to present a synthesis of the data sets and models, disseminate them to the community for further research, and identify mechanisms used to expand the temporal and spatial extent of shortâterm observatoryâscale data collection efforts
Gas dynamics in high-luminosity polarized He-3 targets using diffusion and convection
The dynamics of the movement of gas is discussed for two-chambered polarized
He-3 target cells of the sort that have been used successfully for many
electron scattering experiments. A detailed analysis is presented showing that
diffusion is a limiting factor in target performance, particularly as these
targets are run at increasingly high luminosities. Measurements are presented
on a new prototype polarized He-3 target cell in which the movement of gas is
due largely to convection instead of diffusion. NMR tagging techniques have
been used to visualize the gas flow, showing velocities along a
cylindrically-shaped target of between 5-80 cm/min. The new target design
addresses one of the principle obstacles to running polarized He-3 targets at
substantially higher luminosities while simultaneously providing new
flexibility in target geometry.Comment: First revision: 14 pages, 9 figures, submitted to Phys. Rev. C. We
have shortened our discussion of the limitations inherent in various
historical He-3 targets, and we have added a discussion exploring the optimal
performance that can be expected from a suitably modified target based on
diffusion-based mixing. A reference (Jones et. al.) was added. The results we
present have not change
Measurements of the Electric Form Factor of the Neutron up to Q2=3.4 GeV2 using the Reaction He3(e,e'n)pp
The electric form factor of the neutron was determined from studies of the
reaction He3(e,e'n)pp in quasi-elastic kinematics in Hall A at Jefferson Lab.
Longitudinally polarized electrons were scattered off a polarized target in
which the nuclear polarization was oriented perpendicular to the momentum
transfer. The scattered electrons were detected in a magnetic spectrometer in
coincidence with neutrons that were registered in a large-solid-angle detector.
More than doubling the Q2-range over which it is known, we find GEn = 0.0225
+/- 0.0017 (stat) +/- 0.0024 (syst), 0.0200 +/- 0.0023 +/- 0.0018, and 0.0142
+/- 0.0019 +/- 0.0013 for Q2 = 1.72, 2.48, and 3.41 GeV2, respectively.Comment: submitted to PR
The Power of Environmental Observatories for Advancing Multidisciplinary Research, Outreach, and Decision Support: The Case of the Minnesota River Basin
Observatoryâscale data collection efforts allow unprecedented opportunities for integrative, multidisciplinary investigations in large, complex watersheds, which can affect management decisions and policy. Through the National Science Foundationâfunded REACH (REsilience under Accelerated CHange) project, in collaboration with the Intensively Managed LandscapesâCritical Zone Observatory, we have collected a series of multidisciplinary data sets throughout the Minnesota River Basin in southâcentral Minnesota, USA, a 43,400âkm2 tributary to the Upper Mississippi River. Postglacial incision within the Minnesota River valley created an erosional landscape highly responsive to hydrologic change, allowing for transdisciplinary research into the complex cascade of environmental changes that occur due to hydrology and land use alterations from intensive agricultural management and climate change. Data sets collected include water chemistry and biogeochemical data, geochemical fingerprinting of major sediment sources, highâresolution monitoring of river bluff erosion, and repeat channel crossâsectional and bathymetry data following major floods. The data collection efforts led to development of a series of integrative reduced complexity models that provide deeper insight into how water, sediment, and nutrients route and transform through a large channel network and respond to change. These models represent the culmination of efforts to integrate interdisciplinary data sets and science to gain new insights into watershedâscale processes in order to advance management and decision making. The purpose of this paper is to present a synthesis of the data sets and models, disseminate them to the community for further research, and identify mechanisms used to expand the temporal and spatial extent of shortâterm observatoryâscale data collection efforts
Single Spin Asymmetries of Inclusive Hadrons Produced in Electron Scattering from a Transversely Polarized He Target
We report the first measurement of target single-spin asymmetries (A) in
the inclusive hadron production reaction,
+, using a transversely polarized
He target. The experiment was conducted at Jefferson Lab in Hall A using a
5.9-GeV electron beam. Three types of hadrons (,
and proton) were detected in the transverse hadron momentum range 0.54
0.74 GeV/c. The range of for pions was -0.29 -0.23 and for kaons
-0.25 -0.18. The observed asymmetry strongly depends on the type of
hadron. A positive asymmetry is observed for and . A
negative asymmetry is observed for . The magnitudes of the asymmetries
follow . The K and proton
asymmetries are consistent with zero within the experimental uncertainties. The
and asymmetries measured for the He target and
extracted for neutrons are opposite in sign with a small increase observed as a
function of .Comment: Updated version, submitted to Phys. Rev.
Measurement of pretzelosity asymmetry of charged pion production in Semi-Inclusive Deep Inelastic Scattering on a polarized He target
An experiment to measure single-spin asymmetries in semi-inclusive production
of charged pions in deep-inelastic scattering on a transversely polarized
He target was performed at Jefferson Lab in the kinematic region of
and . The pretzelosity asymmetries on
He, which can be expressed as the convolution of the
transverse momentum dependent distribution functions and the Collins
fragmentation functions in the leading order, were measured for the first time.
Using the effective polarization approximation, we extracted the corresponding
neutron asymmetries from the measured He asymmetries and cross-section
ratios between the proton and He. Our results show that for both
on He and on the neutron the pretzelosity asymmetries are
consistent with zero within experimental uncertainties.Comment: 6 pages, 3 figures; enlarged the legends in Fig.3; added 3 citation
Double Spin Asymmetries of Inclusive Hadron Electroproductions from a Transversely Polarized Target
We report the measurement of beam-target double-spin asymmetries
() in the inclusive production of identified hadrons,
+, using a longitudinally
polarized 5.9 GeV electron beam and a transversely polarized
target. Hadrons (, and proton) were detected at
16 with an average momentum =2.35 GeV/c and a transverse
momentum () coverage from 0.60 to 0.68 GeV/c. Asymmetries from the
target were observed to be non-zero for production
when the target was polarized transversely in the horizontal plane. The
and asymmetries have opposite signs, analogous to the
behavior of in semi-inclusive deep-inelastic scattering.Comment: Published in PRC (92.015207), nuclear experiment, high-energy
experimen
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