1,572 research outputs found
Recent results of the STAR high-energy polarized proton-proton program at RHIC at BNL
The STAR experiment at the Relativistic Heavy-Ion Collider (RHIC) at
Brookhaven National Laboratory (BNL) is carrying out a spin physics program
colliding transverse or longitudinal polarized proton beams at
GeV to gain a deeper insight into the spin structure and
dynamics of the proton. These studies provide fundamental tests of Quantum
Chromodynamics (QCD).
One of the main objectives of the STAR spin physics program is the
determination of the polarized gluon distribution function through a
measurement of the longitudinal double-spin asymmetry, , for various
processes. Recent results will be shown on the measurement of for
inclusive jet production, neutral pion production and charged pion production
at GeV. In addition to these measurements involving longitudinal
polarized proton beams, the STAR collaboration has performed several important
measurements employing transverse polarized proton beams. New results on the
measurement of the transverse single-spin asymmetry, , for forward
neutral pion production and the first measurement of for mid-rapidity
di-jet production will be discussed.Comment: 8 pages, 5 figures, Invited talk given at the 17th International Spin
Physics Symposium (SPIN 2006), October 2006, Kyoto, Japa
Longitudinal Spin Asymmetry and Cross Section of Inclusive pi0 Production in Polarized p+p Collisions at RHIC
We present the first measurement of the cross section and the double
longitudinal spin asymmetry of inclusive pi0 production in polarized p+p
collisions at Sqrt(s) = 200 GeV at mid-rapidity with the STAR detector, using
the barrel electromagnetic calorimeter. The measured cross section is compared
to NLO pQCD calculations and can provide constraints on the pion fragmentation
functions. Fragmentation is studied directly by measuring the momentum fraction
of pi0 in jets, a quantity that is affected by the fragmentation process and
jet reconstruction effects. The double longitudinal spin asymmetry is compared
to NLO pQCD calculations based on different assumptions for the gluon
polarization in the nucleon to provide constraints on delta g/g. At the present
level of statistics the measured asymmetry disfavors a large positive gluon
polarization, but can not yet distinguish between other scenarios.Comment: 4 pages, 2 figures, submitted to the proceedings of the 17th
International Spin Physics Symposium (SPIN2006), Kyoto, Japan, October 2 to
7, 200
Selected results on Strong and Coulomb-induced correlations from the STAR experiment
Using recent high-statistics STAR data from Au+Au and Cu+Cu collisions at
full RHIC energy I discuss strong and Coulomb-induced final state interaction
effects on identical () and non-identical () particle
correlations. Analysis of correlations reveals the strong and
Coulomb-induced FSI effects allowing for the first time to estimate space
extension of and sources and average shift between them. Source
imaging technique providing clean separation of these effects from effects due
to the source function itself is applied to one-dimensional relative momentum
correlation function of identical pions. For low momentum pions and/or
non-central collisions large departure from a single-Gaussian shape is
observed
Measurement of Sivers Asymmetries for Di-jets in \sqrt{s}=200 GeV pp Collisions at STAR
Measurement of the transverse spin dependence of the di-jet opening angle in
pp collisions at sqrt{s}=200 GeV has been performed by the STAR collaboration.
An analyzing power consistent with zero has been observed over a broad range in
pseudorapidity sum of the two jets with respect to the polarized beam
direction. A non-zero (Sivers) correlation between transverse momentum
direction of partons in the initial state and transverse spin orientation of
the parent proton has been previously observed in semi-inclusive deep inelastic
scattering (SIDIS).
The present measurements are much smaller than deduced from predictions made
for STAR di-jets based on non-zero quark Sivers functions deduced from SIDIS,
and furthermore indicate that gluon Sivers asymmetries are comparably small.Comment: 4 pages, 3 figures, talk presented at SPIN 2006, Kyoto, October 200
Measurements of Transverse Spin Effects with the Forward Pion Detector of STAR
Measurements by the STAR collaboration of neutral pion production at large
Feynman x (x_F) in the first polarized proton collisions at GeV
were reported previously. Cross sections measured at , 3.8 and 4.0
are found to be consistent with next-to-leading order perturbative QCD
calculations. The analyzing power is consistent with zero at negative x_F and
at positive x_F up to ~0.3, then grows more positive with increasing x_F. This
behavior can be described by phenomenological models including the Sivers
effect, the Collins effect or higher twist contributions in the initial and
final states. Forward calorimetry at STAR has been extended, and there are
plans for further expansion. An integrated luminosity of 6.8 pb^ with
average beam polarization of 60% from online polarimetry measurements was
sampled with the upgraded FPD in the 2006 RHIC run. This data sample will allow
for a detailed map of the \pi^0 analyzing power over kinematic variables
bounded by 0.3 < x_F < 0.6 and 1.2 < p_T < 5.0 GeV/c at GeV. The
expanded FPD has observed multi-photon final states expected to have "jet-like"
characteristics. The transverse spin dependence of jet-like events can
discriminate between the Collins and Sivers effects and lead to further
progress in understanding the origin of single spin asymmetries in forward
particle production. Data were also obtained at GeV for x_F ->
1 to test predictions based on phenomenological fits to earlier STAR results.
Recent results, the status of the analysis of 2006 run data and near-term plans
will be discussed.Comment: 4 pages, 3 figures, to be published in the proceedings of the 17th
International Spin Physics Symposium (SPIN2006), October 2-7, 2006, Kyoto,
Japa
Mental health patients\u27 experiences of being misunderstood
Mental health patients describe âbeing understoodâ as an experience that evokes feelings of importance, worthiness, and empowerment. However, the experience of âbeing misunderstoodâ is more prevalent in patientsâ relationships with health care providers. Negative consequences such as vulnerability, dehumanization, and frustration reveal that being misunderstood has the potential to damage or destroy therapeutic relationships
D-Meson Mixing in Broken SU(3)
A fit of amplitudes to the experimental branching ratios to two mesons is
used to construct a new estimate of neutral mixing which includes
breaking. The result is dominated by the experimental uncertainties. This
suggests that the charm sector may not be as sensitive to new physics as
previously thought and that long-distance calculations may not be useful.Comment: 12 pages, LaTeX, no figure
Ăkobilanz von Rind-, Schweine- und GeflĂŒgelfleisch aus konventionellen, tierfreundlichen und biologischen Produktionssystemen
The study compared the environmental impacts of different production systems (conventional, increased animal welfare label and organic) for beef, pork and chicken meat at the farm gate using model farms based on Swiss real farm data. Results showed that feeding and feed production had a high influence, particularly for monogastric animals. Organic farming had lower mineral resource use and ecotoxicity due to the ban of mineral fertilisers and pesticides but had a lower productivity per area, which influenced several impact categories such as eutrophication and land use negatively when expressed per kg live weight. Fundamentally, most of the decisive parameters for the environmental impacts of a production system turned out to be generally valid for both conventional and organic production
Isolation and characterization of a spontaneously immortalized bovine retinal pigmented epithelial cell line
<p>Abstract</p> <p>Background</p> <p>The Retinal Pigmented Epithelium (RPE) is juxtaposed with the photoreceptor outer segments of the eye. The proximity of the photoreceptor cells is a prerequisite for their survival, as they depend on the RPE to remove the outer segments and are also influenced by RPE cell paracrine factors. RPE cell death can cause a progressive loss of photoreceptor function, which can diminish vision and, over time, blindness ensues. Degeneration of the retina has been shown to induce a variety of retinopathies, such as Stargardt's disease, Cone-Rod Dystrophy (CRD), Retinitis Pigmentosa (RP), Fundus Flavimaculatus (FFM), Best's disease and Age-related Macular Degeneration (AMD). We have cultured primary bovine RPE cells to gain a further understanding of the mechanisms of RPE cell death. One of the cultures, named tRPE, surpassed senescence and was further characterized to determine its viability as a model for retinal diseases.</p> <p>Results</p> <p>The tRPE cell line has been passaged up to 150 population doublings and was shown to be morphologically similar to primary cells. They have been characterized to be of RPE origin by reverse transcriptase PCR and immunocytochemistry using the RPE-specific genes <it>RPE65 </it>and <it>CRALBP </it>and RPE-specific proteins RPE65 and Bestrophin. The tRPE cells are also immunoreactive to vimentin, cytokeratin and zonula occludens-1 antibodies. Chromosome analysis indicates a normal diploid number. The tRPE cells do not grow in suspension or in soft agar. After <sup>3</sup>H thymidine incorporation, the cells do not appear to divide appreciably after confluency.</p> <p>Conclusion</p> <p>The tRPE cells are immortal, but still exhibit contact inhibition, serum dependence, monolayer growth and secrete an extra-cellular matrix. They retain the <it>in-vivo </it>morphology, gene expression and cell polarity. Additionally, the cells endocytose exogenous melanin, A2E and purified lipofuscin granules. This cell line may be a useful <it>in-vitro </it>research model for retinal maculopathies.</p
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