843 research outputs found
Studies of Transverse Momentum Dependent Parton Distributions and Bessel Weighting
In this paper we present a new technique for analysis of transverse momentum
dependent parton distribution functions, based on the Bessel weighting
formalism. The procedure is applied to studies of the double longitudinal spin
asymmetry in semi-inclusive deep inelastic scattering using a new dedicated
Monte Carlo generator which includes quark intrinsic transverse momentum within
the generalized parton model. Using a fully differential cross section for the
process, the effect of four momentum conservation is analyzed using various
input models for transverse momentum distributions and fragmentation functions.
We observe a few percent systematic offset of the Bessel-weighted asymmetry
obtained from Monte Carlo extraction compared to input model calculations,
which is due to the limitations imposed by the energy and momentum conservation
at the given energy/Q2. We find that the Bessel weighting technique provides a
powerful and reliable tool to study the Fourier transform of TMDs with
controlled systematics due to experimental acceptances and resolutions with
different TMD model inputs.Comment: 30 pages, 8 figures, enhanced discussion and interpretation of
results, new section on errors with an appendix, added references. Accepted
for publication in JHE
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
Beam Single-Spin Asymmetry in Semi-Inclusive Deep Inelastic Scattering
We calculate, in a model, the beam spin asymmetry in semi-inclusive jet
production in deep inelastic scattering. This twist-3, -odd observable is
non-zero due to final state strong interactions. With reasonable choices for
the parameters, one finds an asymmetry of several percent, about the size seen
experimentally. We present the result both as an explicit asymmetry calculation
and as a model calculation of the new transverse-momentum dependent
distribution function .Comment: 10 pages, 6 figures; minor changes made in the discussion; version
accepted for publicatio
Are there approximate relations among transverse momentum dependent distribution functions?
Certain exact relations among transverse momentum dependent parton
distribution functions due to QCD equations of motion turn into approximate
ones upon the neglect of pure twist-3 terms. On the basis of available data
from HERMES we test the practical usefulness of one such
``Wandzura-Wilczek-type approximation'', namely of that connecting
h_{1L}^{\perp(1)a}(x) to h_L^a(x), and discuss how it can be further tested by
future CLAS and COMPASS data.Comment: 9 pages, 3 figure
Transverse-Momentum Distributions and Spherical Symmetry
Transverse-momentum dependent parton distributions (TMDs) are studied in the
framework of quark models. In particular, quark model relations among TMDs are
reviewed and their physical origin is discussed in terms of rotational-symmetry
properties of the nucleon state in its rest frame.Comment: 8 pages, 2 figures, prepared for the workshop "30 years of strong
interactions", Spa, Belgium, 6-8 April 201
Transverse Spin Structure of the Nucleon through Target Single Spin Asymmetry in Semi-Inclusive Deep-Inelastic Reaction at Jefferson Lab
Jefferson Lab (JLab) 12 GeV energy upgrade provides a golden opportunity to
perform precision studies of the transverse spin and
transverse-momentum-dependent structure in the valence quark region for both
the proton and the neutron. In this paper, we focus our discussion on a
recently approved experiment on the neutron as an example of the precision
studies planned at JLab. The new experiment will perform precision measurements
of target Single Spin Asymmetries (SSA) from semi-inclusive electro-production
of charged pions from a 40-cm long transversely polarized He target in
Deep-Inelastic-Scattering kinematics using 11 and 8.8 GeV electron beams. This
new coincidence experiment in Hall A will employ a newly proposed solenoid
spectrometer (SoLID). The large acceptance spectrometer and the high polarized
luminosity will provide precise 4-D (, , and ) data on the
Collins, Sivers, and pretzelocity asymmetries for the neutron through the
azimuthal angular dependence. The full 2 azimuthal angular coverage in the
lab is essential in controlling the systematic uncertainties. The results from
this experiment, when combined with the proton Collins asymmetry measurement
and the Collins fragmentation function determined from the ee collision
data, will allow for a quark flavor separation in order to achieve a
determination of the tensor charge of the d quark to a 10% accuracy. The
extracted Sivers and pretzelocity asymmetries will provide important
information to understand the correlations between the quark orbital angular
momentum and the nucleon spin and between the quark spin and nucleon spin.Comment: 23 pages, 13 figures, minor corrections, matches published versio
Transversity and Transverse Spin in Nucleon Structure through SIDIS at Jefferson Lab
The JLab 12 GeV upgrade with a proposed solenoid detector and the CLAS12
detector can provide the granularity and three-dimensional kinematic coverage
in longitudinal and transverse momentum, , with to precisely measure the leading twist
chiral-odd and -odd quark distribution and fragmentation functions in SIDIS.
The large experimental reach of these detectors with a 12 GeV CEBAF at JLab
makes it {\em ideal} to obtain precise data on the {\em valence-dominated}
transversity distribution function and to access the tensor charge.Comment: 7 Pages, 2 figures. Summary of the working group on Transversity and
Transverse Spin Physics, from the workshop, "Inclusive and Semi-Inclusive
Spin Physics with High Luminosity and LargeAcceptance at 11 GeV", Thomas
Jefferson National Accelerator Facility (JLAB), December 13-14, 2006,
Jefferson Lab, Newport News, VA USA. Serves as input for the Nuclear Physics
Long Range Plan on QCD and Hadron Physic
The involvement of multiple thrombogenic and atherogenic markers in premature coronary artery disease
OBJECTIVE: To examine the association of atherogenic and thrombogenic markers and lymphotoxin-alfa gene mutations with the risk of premature coronary disease. METHODS: This cross-sectional, case-control, age-adjusted study was conducted in 336 patients with premature coronary disease (;50% luminal reduction) or a previous myocardial infarction. The laboratory data evaluated included thrombogenic factors (fibrinogen, protein C, protein S, and antithrombin III), atherogenic factors (glucose and lipid profiles, lipoprotein(a), and apolipoproteins AI and B), and lymphotoxin-alfa mutations. Genetic variability of lymphotoxin-alfa was determined by polymerase chain reaction analysis. RESULTS: Coronary disease patients exhibited lower concentrations of HDL-cholesterol and higher levels of glucose, lipoprotein(a), and protein S. The frequencies of AA, AG, and GG lymphotoxin-alfa mutation genotypes were 55.0%, 37.6%, and 7.4% for controls and 42.7%, 46.0%, and 11.3% for coronary disease patients (p = 0.02), respectively. Smoking, dyslipidemia, family history, and lipoprotein(a) and lymphotoxin-alfa mutations in men were independent variables associated with coronary disease. The area under the curve (C-statistic) increased from 0.779 to 0.802 (
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