4,378 research outputs found
Single spin asymmetries from a single Wilson loop
We study the leading-power gluon transverse momentum dependent distributions
(TMDs) of relevance to the study of asymmetries in the scattering off
transversely polarized hadrons. Next-to-leading-order perturbative calculations
of these TMDs show that at large transverse momentum they have common dynamical
origins, but that in the limit of small longitudinal momentum fraction only
one origin remains. We find that in this limit only the dipole-type gluon TMDs
survive and become identical to each other. At small they are all given by
the expectation value of a single Wilson loop inside the transversely polarized
hadron, the so-called spin-dependent odderon. This universal origin of
transverse spin asymmetries at small is of importance to current and future
experimental studies, paving the way to a better understanding of the role of
gluons in the three-dimensional structure of spin-polarized protons.Comment: 5 pages, 1 figure. Various changes to the text, additional
references, conclusions unchanged, version accepted for publication in
Physical Review Letter
Polarization effects in double open-charm production at LHCb
Double open-charm production is one of the most promising channels to
disentangle single from double parton scattering (DPS) and study different
properties of DPS. Several studies of the DPS contributions have been made. A
missing ingredient so far has been the study of polarization effects, arising
from spin correlations between the two partons inside an unpolarized proton. We
investigate the impact polarization has on the double open-charm cross section.
We show that the longitudinally polarized gluons can give significant
contributions to the cross section, but for most of the considered kinematic
region only have a moderate effect on the shape. We compare our findings to the
LHCb data in the D0D0 final state, identify observables where polarization does
have an impact on the distribution of the final state particles, and suggest
measurements which could lead to first experimental indications of, or limits
on, polarization in DPS.Comment: 16 pages, 13 figure
Effects of TMD evolution and partonic flavor on annihilation into hadrons
We calculate the transverse momentum dependence in the production of two
back-to-back hadrons in electron-positron annihilations at the medium/large
energy scales of BES-III and BELLE experiments. We use the parameters of the
transverse-momentum-dependent (TMD) fragmentation functions that were recently
extracted from the semi-inclusive deep-inelastic-scattering multiplicities at
low energy from HERMES. TMD evolution is applied according to different
approaches and using different parameters for the nonperturbative part of the
evolution kernel, thus exploring the sensitivity of our results to these
different choices and to the flavor dependence of parton fragmentation
functions. We discuss how experimental measurements could discriminate among
the various scenarios.Comment: 33 pages, 10 composite figures, JHEP style fil
A new probe for measuring electrolytic conductance
A conductance cell of which the electrodes are provided with a 110 nm thick Ta2O5 insulating film is proposed and realized. The stable and very low impedance of the total oxide/solution interface largely reduces interference from redox processes. Measurement results, given as an output voltage between 10 and 600 mV as a function of the specific resistance between 0.1 and 8 k¿, are shown to be in agreement with theoretically calculated results, both at the constant current and constant voltage mode of operation
Weak Coulomb blockade effect in quantum dots
We develop the general non-equilibrium theory of transport through a quantum
dot, including Coulomb Blockade effects via a 1/N expansion, where N is the
number of scattering channels. At lowest order we recover the Landauer formula
for the current plus a self-consistent equation for the dot potential. We
obtain the leading corrections and compare with earlier approaches. Finally, we
show that to leading and next leading order in 1/N there is no interaction
correction to the weak localization, in contrast to previous theories, but
consistent with experiments by Huibers et al. [Phys. Rev. Lett. 81, 1917
(1998)], where N=4.Comment: 4 pages, 2 figures. Published versio
Chemically modified field effect transistors: the effect of ion-pair association on the membrane potentials
A theoretical model has been developed which relates physically accessible parameters to the formation of a membrane potential. The description is an extension of a theoretical description presented previously by our group, now including divalent cations and ion-pair association. Simulations of the overall membrane potential reveal several factors that may lead to non-Nernstian response curves. For monovalent and divalent cations a reduction in the slope of the response curve (sub-Nernstian response) should virtually always be expected when ion-pair association takes place in the membrane. Ion-pair association of divalent cations and sample anions can lead to a super-Nernstian response. A diffusion potential generally reduces the Nernstian slope of the response curve. In addition, several experimental results are described which illustrate and confirm our theoretical model
Progress in osteoporosis and fracture prevention: focus on postmenopausal women
In the past decade, we have witnessed a revolution in osteoporosis diagnosis and therapeutics. This includes enhanced understanding of basic bone biology, recognizing the severe consequences of fractures in terms of morbidity and short-term re-fracture and mortality risk and case finding based on clinical risks, bone mineral density, new imaging approaches, and contributors to secondary osteoporosis. Medical interventions that reduce fracture risk include sufficient calcium and vitamin D together with a wide spectrum of drug therapies (with antiresorptive, anabolic, or mixed effects). Emerging therapeutic options that target molecules of bone metabolism indicate that the next decade should offer even greater promise for further improving our diagnostic and treatment approaches
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