1,089 research outputs found
Studies of spin-orbit correlations at JLAB
Studies of single spin asymmetries for pion electroproduction in
semi-inclusive deep-inelastic scattering are presented using the polarized
\sim6 GeV electrons from at the Thomas Jefferson National Accelerator Facility
(JLab) and the Continuous Electron Beam Accelerator Facility (CEBAF) Large
Acceptance Spectrometer (CLAS) with the Inner Calorimeter. The cross section
versus the azimuthal angle {\phi}_h of the produced neutral pion has a
substantial sin {\phi}_h amplitude. The dependence of this amplitude on Bjorken
x_B and on the pion transverse momentum is extracted and compared with
published data.Comment: proceedings of SPIN2010 conference (September-October 2010,
Juelich-Germany
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Assessing the motivational effects of ethanol in mice using a discrete-trial current-intensity intracranial self-stimulation procedure.
BackgroundAlcohol (ethanol) produces both rewarding and aversive effects, and sensitivity to these effects is associated with risk for an alcohol use disorder (AUD). Measurement of these motivational effects in animal models is an important but challenging aspect of preclinical research into the neurobiology of AUD. Here, we evaluated whether a discrete-trial current-intensity intracranial self-stimulation (ICSS) procedure can be used to assess both reward-enhancing and aversive responses to ethanol in mice.MethodsMale and female C57BL/6J mice were surgically implanted with bipolar stimulating electrodes targeting the medial forebrain bundle and trained on a discrete-trial current-intensity ICSS procedure. Mice were tested for changes in response thresholds after various doses of ethanol (0.5 g/kg-1.75 g/kg; n = 5-7 per dose), using a Latin square design.ResultsA 1 g/kg dose of ethanol produced a significant reward-enhancement (i.e., lowered response thresholds), whereas a 1.75 g/kg dose produced an aversive effect (elevated response thresholds). Ethanol doses from 1 to 1.75 g/kg increased response latencies as compared to saline treatment.ConclusionsThe discrete-trial current-intensity ICSS procedure is an effective assay for measuring both reward-enhancing responses to ethanol as well as aversive responses in the same animal. This should prove to be a useful tool for assessing the effects of experimental manipulations on the motivational effects of ethanol in mice
Monte Carlo simulation of single spin asymmetries in pion-proton collisions
We present Monte Carlo simulations of both the Sivers and the Boer-Mulders
effects in the polarized Drell-Yan
process at the center-of-mass energy GeV reachable at
COMPASS with pion beams of energy 100 GeV. For the Sivers effect, we adopt two
different parametrizations for the Sivers function to explore the statistical
accuracy required to extract unambiguous information on this parton density. In
particular, we verify the possibility of checking its predicted sign change
between Semi-Inclusive Deep-Inelastic Scattering (SIDIS) and Drell-Yan
processes, a crucial test of nonperturbative QCD. For the Boer-Mulders effect,
because of the lack of parametrizations we can make only guesses. The goal is
to explore the possibility of extracting information on the transversity
distribution, the missing piece necessary to complete the knowledge of the
nucleon spin structure at leading twist, and the Boer-Mulders function, which
is related to the long-standing problem of the violation of the Lam-Tung sum
rule in the unpolarized Drell-Yan cross section.Comment: RevTeX, 13 pages, 7 figures included in .eps forma
Quark orbital angular momentum: can we learn about it from GPDs and TMDs?
It is known how to access information on quark orbital angular momentum from
generalized parton distribution functions, in a certain specified framework. It
is intuitively expected, that such information can be accessed also through
transverse momentum dependent distribution functions, but not known how. Now
quark models provide promising hints. Recent results are reviewed.Comment: proceeding of the "4th Workshop on Exclusive Reactions at High
Momentum Transfer," 18-21 May 2010, Jefferson La
Predictions for double spin asymmetry A_{LT} in Semi Inclusive DIS
In the leading order of QCD parton model of Semi Inclusive Deep Inelastic
Scattering (SIDIS) the double spin asymmetry arises due to the
longitudinal polarization of quarks in the transversely polarized nucleon. The
corresponding weighted distribution function can be
related to ordinary helicity distribution measured in DIS. Using
recent parameterizations for (un)polarized distribution and fragmentation
functions we calculated asymmetry on transversely polarized proton and
deuteron targets for different types hadron production. The predictions are
given for COMPASS, HERMES and JLab energies. The role of Lorentz invariance
relations and positivity constraints are discussed.Comment: The new conventional definition of asymmetry is adopted -- the factor
two is added. The figures are rescaled by factor tw
Performance of the Electromagnetic Calorimeter of the HERMES Experiment
The performance of the electromagnetic calorimeter of the HERMES experiment
is described. The calorimeter consists of 840 radiation resistant F101
lead-glass counters. The response to positrons up to 27.5 GeV, the comparison
between the measured energy and the momentum reconstructed from tracking,
long-term stability, hadron rejection and neutral meson invariant mass
reconstruction are shown.Comment: 22 pages, 13 figures, LaTeX, accepted by NI
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