5,721 research outputs found
Pomeron-Odderon interference effects in electroproduction of
We review the results of our studies on the charge and the spin asymmetries
in the electroproduction of which are the observables sensitive
to the Pomeron-Odderon interference.Comment: 5 pages LATEX, Talk given by L.Sz. at the 9th Int. High-Energy
Physics Conference QCD '02, Montpellier, France, 2-9th July 200
Saturation Effects in Deep Inelastic Scattering at low and its Implications on Diffraction
We present a model based on the concept of saturation for small and
small . With only three parameters we achieve a good description of all Deep
Inelastic Scattering data below . This includes a consistent treatment
of charm and a successful extrapolation into the photoproduction regime. The
same model leads to a roughly constant ratio of diffractive and inclusive cross
section.Comment: 24 pages, 12 figures, Latex-fil
Hunting the QCD-Odderon in hard diffractive electroproduction of two pions
Charge asymmetries in diffractive electroproduction of two mesons are
proportional to the interference of Pomeron and Odderon exchange amplitudes. We
calculate in the framework of QCD and in the Born approximation a
forward-backward charge asymmetry which turns out to be sizable in a
kinematical domain accessible to HERA experiments. We predict a distinctive
dependence of this asymmetry on the invariant mass of the two pions. Testing
this prediction is a crucial step in the discovery of the QCD-Odderon.Comment: 13 pages LATEX, 6 .eps figures, numerical error corrected, new
figures,main conclusions not change
Spin dependent structure function g_1 at low x and low Q^2
Theoretical description of the spin dependent structure function g_1(x,Q^2)
in the region of low values of x and Q^2 is presented. It contains the Vector
Meson Dominance contribution and the QCD improved parton model suitably
extended to the low Q^2 domain. Theoretical predictions are compared with the
recent experimental data in the low x, low Q^2 region
Double diffractive rho-production in gamma^* gamma^* collisions
We present a first estimate of the cross-section for the exclusive process
gamma^*_L (Q_1^2) gamma^*_L(Q_2^2) -> rho^0_L rho^0_L, which will be studied in
the future high energy e^+ e^- linear collider. As a first step, we calculate
the Born order approximation of the amplitude for longitudinally polarized
virtual photons and mesons, in the kinematical region s >> -t, Q_1^2, Q_2^2.
This process is completely calculable in the hard region Q_1^2, Q_2^2 >>
Lambda^2_{QCD}. We perform most of the steps in an analytical way. The
resulting cross-section turns out to be large enough for this process to be
measurable with foreseen luminosity and energy, for Q_1^2 and Q_2^2 in the
range of a few GeV^2.Comment: 25 pages, 5 figures. Published version in EPJC. Minor changes and
several references added with respect to v
Strategien zur Reduzierung der Kupferaufwandmengen im ökologischen Kartoffelanbau – Projekt “ÖKO-SIMPHYT“
Potato late blight (Phytophthora infestans) is still an unsolved problem in organic farming. Up to now the disease can only be controlled by copper fungicides. Our project is aiming to reduce the application of copper-containing fungicides by introduc-tion of the new blight forecasting system “ÖKO-SIMPHYT” based on meteorological parameters. Primary stem infections should be reduced by seed treatment with copper fungicides thus to postpone the beginning of the blight epidemic as well as the start of spraying. To control secondary infections on the foliage, fungicide strategies should be elaborated to achieve best efficacy with reduced amounts of copper. Therefore copper amounts and spraying intervals should be adjusted to the infection pressure. Based on the biological and epidemiological conditions for primary and secondary infections the new developed potato blight forecast system ÖKO-SIMPHYT should be optimized
Combined electrical transport and capacitance spectroscopy of a field effect transistor
We have measured both the current-voltage (-)
and capacitance-voltage (-) characteristics of a
field effect transistor. From the measured capacitance
we calculate the electron surface density and show that its gate voltage
dependence follows the theoretical prediction resulting from the
two-dimensional free electron model. This model allows us to fit the measured
- characteristics over the \emph{entire range} of
. Combining this experimental result with the measured
current-voltage characteristics, we determine the field effect mobility as a
function of gate voltage. We show that for our device this improved combined
approach yields significantly smaller values (more than a factor of 4) of the
electron mobility than the conventional analysis of the current-voltage
characteristics only.Comment: to appear in Applied Physics Letter
The casuality and/or energy-momentum conservation constraints on QCD amplitudes in small x regime
The causality and/or the energy-momentum constraints on the amplitudes of
high energy processes are generalized to QCD. The constraints imply that the
energetic parton may experience at most one inelastic collision only and that
the number of the constituents in the light cone wave function of the
projectile is increasing with the collision energy and the atomic number.Comment: 24 pages,8 figures. The paper is streamlined, some references are
changed and misprints are eliminate
On the behaviour of single scale hard small processes in QCD near the black disc limit
We argue that at sufficiently small Bjorken where pQCD amplitude rapidly
increases with energy and violates probability conservation the shadowing
effects in the single-scale small hard QCD processes can be described by an
effective quantum field theory of interacting quasiparticles. The
quasiparticles are the perturbative QCD ladders. We find, within the WKB
approximation, that the smallness of the QCD coupling constant ensures the
hierarchy among many-quasiparticle interactions evaluated within physical
vacuum and in particular, the dominance in the Lagrangian of the triple
quasiparticle interaction. It is explained that the effective field theory
considered near the perturbative QCD vacuum contains a tachyon relevant for the
divergency of the perturbative QCD series at sufficiently small . We solve
the equations of motion of the effective field theory within the WKB
approximation and find the physical vacuum and the transitions between the
false (perturbative) and physical vacua. Classical solutions which dominate
transitions between the false and physical vacua are kinks that cannot be
decomposed into perturbative series over the powers of . These kinks
lead to color inflation and the Bose-Einstein condensation of quasiparticles.
The account of the quantum fluctuations around the WKB solution reveals the
appearance of the "massless" particles-- "phonons". It is explained that
"phonons" are relevant for the black disc behaviour of small processes,
leading to a Froissart rise of the cross-section. The condensation of the
ladders produces a color network occupying a "macroscopic" longitudinal volume.
We discuss briefly the possible detection of new QCD effects.Comment: 24 pages, 1 Figure. References added, and several misprints
eliminate
Kupferminimierungsstrategien im ökologischen Kartoffelanbau – Projekt “ÖKO-SIMPHYT“: Erste Erfahrungen aus dem norddeutschen Freiland
In the research project „ÖKO-SIMPHYT“ different strategies are tested to reduce the copper application for Phytophthora infestans in organic potato cultivation. Within the first two years of our research a reduction of the total amount of copper per hectare could be accomplished when applying the new developed forecast system ÖKO-SIMPHYT. With this decision support system a reduction of copper up to 46% was possible, when the infection pressure was relatively low. These first results have now to be proven under high infection pressure conditions. Experiments were carried out in the greenhouse to test the rain stability of copper and contacting agents. It could be proved that precipitation of 30 mm is able to reduce the degree of a copper treatment by up to 25%
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