3,440 research outputs found
Single Spin Asymmetry at Large x_F and k_T
The large single spin asymmetries observed at high momentum fractions x_F and
transverse momenta k_T in p^\uparrow p -> \pi(x_F,k_T)+X as well as in pp ->
\Lambda^\uparrow(x_F,k_T)+X suggest that soft helicity flip processes are
coherent with hard scattering. Such coherence can be maintained if x_F -> 1 as
k_T -> \infty, while k_T^2(1-x_F) \sim \Lambda_QCD^2 stays fixed. The entire
hadron wave function, rather than a single quark, then contributes to the
scattering process. Analogous coherence effects have been seen experimentally
in the Drell-Yan process at high x_F. We find that the p^\uparrow p ->
\pi(x_F,k_T)+X production amplitudes have large dynamic phases and that
helicity flip contributions are unsuppressed in this limit, giving rise to
potentially large single spin asymmetries.Comment: 11 pages, 2 figures. v2: References and a preprint number added.
Calculation of section 4 modified. v3: Minor changes in text. Version to be
published in JHE
Spin asymmetry at large x_F and k_T
We suggest that the large single spin asymmetries observed at high momentum
fractions x_F and transverse momenta k_T of the pion in p^\uparrow p ->
\pi(x_F,k_T)+X arise from the coherence of the soft interactions with the hard
parton scattering process. Such coherence can be maintained if x_F -> 1 as k_T
-> \infty, while k_T^2(1-x_F) ~ \Lambda_{QCD}^2 stays fixed. Analogous
coherence effects have been seen experimentally in the Drell-Yan process at
high x_F. We find that the p^\uparrow p -> \pi X production amplitudes have
large dynamic phases and that helicity flip contributions are unsuppressed in
this limit, giving rise to potentially large single spin asymmetries.Comment: 3 pages, 1 figure. Talk given at EPS HEP 2007, Mancheste
Thrilling Tales of the Tuscania - From the Rolling Deep
All good stories should have an introduction, and as the collaborators wrote distinct accounts of the sinking of the Tuscania, it is necessary to harmonize the stories somewhat. It was the original intention of the editor to combine the separate narratives of the authors into a single story, but each was distinct enough to merit printing entire. Suffice to say that each got off the boat alright, which seemed to be the principal object in view at the time. The editor met Shorty Hoyer a month or so later and he was very willingly chopping wood in France. Nevertheless, we are proud of the fact that we had five Ames foresters on the Tuscania and are more than glad that they are still with us. -Editor’s Note
Application of ERTS-1 Imagery to Flood Inundation Mapping
Application of ERTS-1 imagery to flood inundation mapping in East and West Nishnabotna basins of southwestern Iow
Einfluss des ökologischen Landbaus auf unterschiedliche Humuspools im Boden und Schlussfolgerungen zur Humusbilanzierung
Due to the results of organic matter balancing which showed a very high potential of soil organic matter accumulation in organic farming, a research project was started in spring 2005 with the objective to ascertain this hypothesis. Soil sampling was carried out on different organic and adjacent conventional farms in distinct regions of Ger-many. A comparison of the samples regarding Corg showed only minor differences between organic and conventional farms whereas the more sensitive indicators like Cmic and enzyme activities were more affected. However the main influencing factor of all these indicators in this investigation is soil texture. The cultivation system (inten-sive, extensive, stocking, crop rotation, tillage) is more important than the differentia-tion organic or conventional farming
Realistic and verifiable coherent control of excitonic states in a light harvesting complex
We explore the feasibility of coherent control of excitonic dynamics in light
harvesting complexes, analyzing the limits imposed by the open nature of these
quantum systems. We establish feasible targets for phase and phase/amplitude
control of the electronically excited state populations in the
Fenna-Mathews-Olson (FMO) complex and analyze the robustness of this control
with respect to orientational and energetic disorder, as well as decoherence
arising from coupling to the protein environment. We further present two
possible routes to verification of the control target, with simulations for the
FMO complex showing that steering of the excited state is experimentally
verifiable either by extending excitonic coherence or by producing novel states
in a pump-probe setup. Our results provide a first step toward coherent control
of these complex biological quantum systems in an ultrafast spectroscopy setup.Comment: 12 pages, 8 figure
Interpretation of High Energy String Scattering in terms of String Configurations
High energy string scattering at fixed momentum transfer, known to be
dominated by Regge trajectory exchange, is interpreted by identifying families
of string states which induce each type of trajectory exchange. These include
the usual leading trajectory and its daughters as
well as the ``sister'' trajectories and their
daughters. The contribution of the sister to high energy scattering
is dominated by string excitations in the mode. Thus, at large ,
string scattering is dominated by wee partons, consistently with a picture of
string as an infinitely composite system of ``constituents'' which carry zero
energy and momentum.Comment: 14 pages, phyzzx, psfig required, Florida Preprint UFIFT-94-
A Participatory Process to Develop a Landslide Warning System: Paradoxes of Responsibility Sharing in a Case Study in Upper Austria
During a participatory process in Gmunden, Austria, the organizational and responsibility-sharing arrangements for a landslide warning system proved to be contested issues. While questions on the warning system technology and the distribution of information, including the alarm for evacuation, could be resolved with the support of experts, controversies arose on the financial and legal responsibilities that ensure long-term and effective monitoring for the protection of the landslide-prone community. This paper examines how responsibilities can be shared among the residents, experts, and public authorities during the design and operation of landslide warning systems. In particular, we discuss the outcome and implications of three stakeholder workshops where participants deliberated on warning-system options that, in turn, were based on a discourse analysis of extensive stakeholder interviews. The results of the case study show that an end-user orientation requires the consideration of stakeholder worldviews, interests, and conflicts. Paradoxically, the public did not fully support their own involvement in the maintenance and control of the warning system, but the authorities promoted shared responsibility. Deliberative planning does not then necessarily lead to responsibility sharing, but it proved effective as a platform for information and for shared ownership in the warning syste
Anti-IL1ß-monoclonal antibody in two adult patients with PFAPA Syndrome - a single centre experience
Vibration-enhanced quantum transport
In this paper, we study the role of collective vibrational motion in the
phenomenon of electronic energy transfer (EET) along a chain of coupled
electronic dipoles with varying excitation frequencies. Previous experimental
work on EET in conjugated polymer samples has suggested that the common
structural framework of the macromolecule introduces correlations in the energy
gap fluctuations which cause coherent EET. Inspired by these results, we
present a simple model in which a driven nanomechanical resonator mode
modulates the excitation energy of coupled quantum dots and find that this can
indeed lead to an enhancement in the transport of excitations across the
quantum network. Disorder of the on-site energies is a key requirement for this
to occur. We also show that in this solid state system phase information is
partially retained in the transfer process, as experimentally demonstrated in
conjugated polymer samples. Consequently, this mechanism of vibration enhanced
quantum transport might find applications in quantum information transfer of
qubit states or entanglement.Comment: 7 pages, 6 figures, new material, included references, final
published versio
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