945 research outputs found
Constraints on spin-dependent parton distributions at large x from global QCD analysis
We investigate the behavior of spin-dependent parton distribution functions
(PDFs) at large parton momentum fractions x in the context of global QCD
analysis. We explore the constraints from existing deep-inelastic scattering
data, and from theoretical expectations for the leading x -> 1 behavior based
on hard gluon exchange in perturbative QCD. Systematic uncertainties from the
dependence of the PDFs on the choice of parametrization are studied by
considering functional forms motivated by orbital angular momentum arguments.
Finally, we quantify the reduction in the PDF uncertainties that may be
expected from future high-x data from Jefferson Lab at 12 GeV.Comment: 14 pages, 3 figures, 1 tabl
New results on SIDIS SSA from Jefferson Lab
We present studies of single-spin and double-spin asymmetries in
semi-inclusive electroproduction of pions using the CEBAF 6 GeV polarized
electron beam. Kinematic dependences of single and double spin asymmetries have
been measured in a wide kinematic range at CLAS with a polarized NH target.
Significant target-spin and asymmetries have been
observed. The hypothesis of factorization has been tested with -dependence
of the double spin asymmetry.Comment: 4 pages, 6 figure
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
Measurement of Single- and Double-Spin Asymmetries in Deep Inelastic Pion Electroproduction with a Longitudinally Polarized Target
We report the first measurement of the transverse momentum dependence of double-spin asymmetries in semi-inclusive production of pions in deep-inelastic scattering off the longitudinally polarized proton. Data have been obtained using a polarized electron beam of 5.7 GeV with the CLAS detector at the Jefferson Lab (JLab). Modulations of single spin asymmetries over the azimuthal angle between lepton scattering and hadron production planes φ have been measured over a wide kinematic range in Bjorken x and virtual photon squared four-momentum Q2. A significant nonzero sin2φ single spin asymmetry was observed for the first time indicating strong spin-orbit correlations for transversely polarized quarks in the longitudinally polarized proton
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
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
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