493 research outputs found
EXCLUSIVE rho0 AND phi PRODUCTION IN DEEP INELASTIC MUON SCATTERING
No full textAshman J, Badelek B, Baum G, et al. Exclusive Rho 0 and Phi production in deep inelastic muon scattering. Z.Phys. C. 1988;39(2):169-175
Kraichnan-Leith-Batchelor similarity theory and two-dimensional inverse cascades
No full textWe study the scaling properties and Kraichnan-Leith-Batchelor (KLB) theory of forced inverse cascades in generalized two-dimensional (2D) fluids (-turbulence models) simulated at resolution . We consider (surface quasigeostrophic flow), (2D vorticity dynamics) and . The forcing scale is well-resolved, a direct cascade is present and there is no large-scale dissipation. Coherent vortices spanning a range of sizes, most larger than the forcing scale, are present for both and . The active scalar field for contains comparatively few and small vortices. The energy spectral slopes in the inverse cascade are steeper than the KLB prediction in all three systems. Since we stop the simulations well before the cascades have reached the domain scale, vortex formation and spectral steepening are not due to condensation effects; nor are they caused by large-scale dissipation, which is absent. One- and two-point pdfs, hyperflatness factors and structure functions indicate that the inverse cascades are intermittent and non-Gaussian over much of the inertial range for and , while the inverse cascade is much closer to Gaussian and non-intermittent. For the steep spectrum is close to that associated with enstrophy equipartition. Continuous wavelet analysis shows approximate KLB scaling () and () in the interstitial regions between the coherent vortices. Our results demonstrate that coherent vortex formation ( and ) and non-realizability () cause 2D inverse cascades to deviate from the KLB predictions, but that the flow between the vortices exhibits KLB scaling and non-intermittent statistics for and . The results will appear in \cite{BurgessEA2015}, which has been accepted to the \emph{Journal of Fluid Mechanics}
Absorbing new subjects: holography as an analog of photography
No full textI discuss the early history of holography and explore how perceptions, applications, and forecasts of the subject were shaped by prior experience. I focus on the work of Dennis Gabor (1900–1979) in England,Yury N. Denisyuk (b. 1924) in the Soviet Union, and Emmett N. Leith (1927–2005) and Juris Upatnieks (b. 1936) in the United States. I show that the evolution of holography was simultaneously promoted and constrained by its identification as an analog of photography, an association that influenced its assessment by successive audiences of practitioners, entrepreneurs, and consumers. One consequence is that holography can be seen as an example of a modern technical subject that has been shaped by cultural influences more powerfully than generally appreciated.
Conversely, the understanding of this new science and technology in terms of an older one helps
to explain why the cultural effects of holography have been more muted than anticipated by forecasters
between the 1960s and 1990s
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A review of 4/pi/ /hacek C/erenkov ring imaging detectors
No full textThe design choices for 4/pi/ ring imaging /hacek C/erenkov counters -- both those of principle and those of practice -- are reviewed. The progress in construction and the performance of the devices being built for DELPHI and SLD are discussed. 13 refs., 22 figs
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Review of recent progress in the development of Cerenkov Ring Imaging Detectors
No full textThe principle behind the Cherenkov Ring Imaging Detectors (CRIDs) involves focussing the Cherenkov light, emitted by a relativistic charged particle in passing through a radiator medium, onto a high efficiency photocathode which can be in turn read out with good spatial resolution, to localize the point of origin of the photoelectrons. This information permits the reconstruction of the circle of Cherenkov light for each particle above threshold, and hence the determination of the Cherenkov angle to an accuracy of a few percent. The groups currently working on these detectors are discussed, the status of these projects is examined, and progress is reported on the R and D on two 4-pi devices being prepared for physics at the Z. The activities are being done at Fermilab, CERN, and SLAC. 8 refs., 32 figs. (LEW
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Use of elementary particle interactions for radiological imaging
No full textThe potential for the use of inelastic high energy particle reactions to produce radiological images is parable to that of computerized axial tomography at a fraction of the radiation exposure. In addition, the comparison of coherently produced events to the total inelastic cross section should allow a probe of the chemical composition (i.e., average Z) of the material being studied. The performance of this technique is reviewed and some preliminary results using a 5 GeV/c ..pi../sup -/ beam at SLAC are presented
Preliminary results on tests of a Cerenkov ring imaging device employing a photoionizing PWC
No full textA brief description of techniques and problems of ring imaging Cerenkov detectors employing photoionizing PWC's is discussed. Preliminary results on a one dimensional ring imaging device tested at SLAC in May and June of 1978 are then presented. These results include rough measurements of the Cerenkov ring in nitrogen, argon, neon, and helium produced by a collimated positron beam
Penalized FTRL with Time-Varying Constraints
No full textIn this paper we extend the classical Follow-The-Regularized-Leader (FTRL) algorithm to encompass time-varying constraints, through adaptive penalization. We establish sufficient conditions for the proposed Penalized FTRL algorithm to achieve O(t) regret and violation with respect to a strong benchmark X^tmax. Lacking prior knowledge of the constraints, this is probably the largest benchmark set that we can reasonably hope for. Our sufficient conditions are necessary in the sense that when they are violated there exist examples where O(t) regret and violation is not achieved. Compared to the best existing primal-dual algorithms, Penalized FTRL substantially extends the class of problems for which O(t) regret and violation performance is achievable.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Networked System
Lazy Lagrangians for Optimistic Learning With Budget Constraints
No full textWe consider the general problem of online convex optimization with time-varying budget constraints in the presence of predictions for the next cost and constraint functions, that arises in a plethora of network resource management problems. A novel saddle-point algorithm is designed by combining a Follow-The-Regularized-Leader iteration with prediction-adaptive dynamic steps. The algorithm achieves O(T(3β/4) regret and O(T(1+β)/2) constraint violation bounds that are tunable via parameter β ∈ [1/2,1) and have constant factors that shrink with the predictions quality, achieving eventually O(1) regret for perfect predictions. Our work extends the seminal FTRL framework for this new OCO setting and outperforms the respective state-of-the-art greedy-based solutions which naturally cannot benefit from predictions, without imposing conditions on the (unknown) quality of predictions, the cost functions or the geometry of constraints, beyond convexity.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Embedded System
Detectors of Internally Reflected Cherenkov Light (DIRC) for Charged Particle Identification
No full textDetectors of Internally Reflected Cherenkov light (DIRC) are powerful devices for charged particle identification (PID). Indeed, the primary detector to separate kaons and pions up to few GeV/c in the barrel region of the BABAR experiment was based on the DIRC technology and performed extremely well over almost a decade of operation. In the first part of this talk, we will review the DIRC principles (charged particles emit Cherenkov light when crossing fused silica bars; part of the photons are trapped by total internal reflection and propagate in the radiators until a camera where they are detected by photon detectors) and the associated experimental challenges. We will focus on the BABAR ring-imaging Cherenkov detector, the DIRC. After presenting its design, we will summarize its performances such as the experience gained by operating this apparatus at the SLAC PEP-II asymmetric B-Factory, which delivered more than 500/fb of integrated luminosity with a peak luminosity at 1.2 10^34 /cm^2/s. Then, we will describe the R&D program which aims at designing a new generation DIRC detector, able to work at much higher luminosity (and background) while keeping excellent PID performances. This effort, which started during the last years of the BABAR running, has led to a design for the Focusing DIRC detector (FDIRC), which is currently being tested at SLAC in a cosmic ray telescope. The main difference between the BABAR DIRC and the FDIRC is a completely redesigned photon camera: small blocks of fused silica (the same material as the DIRC bars in which charged particles generate the Cherenkov light) including two mirrors and instrumented with fast multi-anode photomultipliers now replace the huge tank filled with ultra-pure water used in the BABAR design. We will also briefly present a concept of DIRC-based detector for PID in the endcap region of a HEP detector, originally designed for the SuperB project, now terminated due to lack of funding
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