10,570 research outputs found
Spin density matrix elements in vector meson leptoproduction
It is reported on an analysis of vector meson leptoproduction at small
Bjorken- and large photon virtuality within an approach that bases on
generalized parton distributions (GPDs). This approach leads to results for
cross sections and spin density matrix elements for and
leptoproduction in fair agreement with experiment.Comment: Report at Spin 2004 Symposium, October 10-16, Trieste, Ital
Transversity in exclusive vector-meson leptoproduction
The role of transversity or helicity-flip generalized parton distributions
(GPDs) in leptoproduction of vector mesons is investigated within the framework
of the handbag approach. The transversity GPDs in combination with twist-3
meson wave functions, occur in the amplitudes for transitions from a
transversely polarized virtual photon to a longitudinal polarized vector meson.
The importance of the transversity GPDs can be examined in some of the spin
density matrix elements and in transverse target spin asymmetries. Using
suitable parametrizations of both helicity-flip and non-flip GPDs, which are
essentially taken from our previous papers, we estimate these observables and
compare the results with available data.Comment: 30 pages, 19 figure
The pion pole in hard exclusive vector-meson leptoproduction
Exploiting a set of generalized parton distributions (GPDs) derived from
analyses of hard exclusive leptoproduction of rho0, phi and pi+ mesons, we
investigate the omega spin density matrix elements (SDMEs) recently measured by
the HERMES collaboration. It turns out from our study that the pion pole is an
important contribution to omega production. It will be treated as a
one-particle exchange since its evaluation from the GPD E-tilde considerably
underestimates its contribution. As an intermediate step of our analysis we
extract the pi-omega transition form factor for photon virtualities less than 4
GeV^2. From our approach we achieve results for the omega SDMEs in good
agreement with the HERMES data. The role of the pion pole in exclusive rho0 and
phi leptoproduction is discussed too.Comment: 27 pages, 33 figure
The exclusive limit of the pion-induced Drell-Yan process
Based on previous studies of hard exclusive leptoproduction of pions in which
the essential role of the pion pole and the transversity generalized parton
distributions has been pointed out, we present predictions for the four partial
cross sections of the exclusive Drell-Yan process, pi^-p -> l^-l^+n.Comment: 14 pages, 6 figure
Patient-reported outcome measures for chronic obstructive pulmonary disease: the exclusion of people with low literacy skills and learning disabilities
<p>Background: Patient-reported outcome measures (PROMs)
are intended to reflect outcomes relevant to patients. They are
increasingly used for healthcare quality improvement. To
produce valid measures, patients should be involved in the
development process but it is unclear whether this usually
includes people with low literacy skills or learning disabilities.
This potential exclusion raises concerns about whether these
groups will be able to use these measures and participate in
quality improvement practices.</p>
<p>Methods: Taking PROMs for chronic obstructive pulmonary disease (COPD) as an exemplar condition, our review
determined the inclusion of people with low literacy skills and
learning disabilities in research developing, validating, and
using 12 PROMs for COPD patients. The studies included in
our review were based on those identified in two existing
systematic reviews and our update of this search.
Results People with low literacy skills and/or learning
disabilities were excluded from the development of
PROMs in two ways: explicitly through the participant
eligibility criteria and, more commonly, implicitly through
recruitment or administration methods that would require
high-level reading and cognitive abilities. None of the
studies mentioned efforts to include people with low literacy skills or learning disabilities.</p>
<p>Conclusion: Our findings suggest that people with low
literacy skills or learning disabilities are left out of the
development of PROMs. Given that implicit exclusion was
most common, researchers and those who administer
PROMs may not even be aware of this problem. Without
effort to improve inclusion, unequal quality improvement
practices may become embedded in the health system.</p>
Initial experiments concerning quantum information processing in rare-earth-ion doped crystals
In this paper initial experiments towards constructing simple quantum gates
in a solid state material are presented. Instead of using specially tailored
materials, the aim is to select a subset of randomly distributed ions in the
material, which have the interaction necessary to control each other and
therefore can be used to do quantum logic operations. The experimental results
demonstrate that part of an inhomogeneously broadened absorption line can be
selected as a qubit and that a subset of ions in the material can control the
resonance frequency of other ions. This opens the way for the construction of
quantum gates in rare-earth-ion doped crystals.Comment: 24 pages, including 12 figure
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