1,235 research outputs found
A Probe of New Physics in Top Quark Pair Production at Colliders
We describe how to probe new physics through examination of the form factors
describing the Ztt couplings via the scattering process e^-e^+->t+tbar. We
focus on experimental methods on how the top quark momentum can be determined
and show how this can be applied to select polarized samples of
pairs through the angular correlations in the final state leptons. We also
study the dependence on the energy and luminosity of an \ee\ collider to probe
a CP violating asymmetry at the level.}Comment: 24 pages in TeXsis (figures available upon request) (revised July
1993
Higgs signals and hard photons at the Next Linear Collider: the -fusion channel in the Standard Model
In this paper, we extend the analyses carried out in a previous article for
-fusion to the case of Higgs production via -fusion within the Standard
Model at the Next Linear Collider, in presence of electromagnetic radiation due
real photon emission. Calculations are carried out at tree-level and rates of
the leading order (LO) processes e^+e^-\rightarrow e^+e^- H \ar e^+e^- b\bar b
and e^+e^-\rightarrow e^+e^- H \ar e^+e^- WW \ar e^+e^- \mathrm{jjjj} are
compared to those of the next-to-leading order (NLO) reactions
e^+e^-\rightarrow e^+e^- H (\gamma)\ar e^+e^- b\bar b \gamma and
e^+e^-\rightarrow e^+e^- H (\gamma)\ar e^+e^- WW (\gamma) \ar e^+e^-
\mathrm{jjjj}\gamma, in the case of energetic and isolated photons.Comment: 12 pages, LaTeX, 5 PostScript figures embedded using epsfig and
bitmapped at 100dpi, complete paper including high definition figures
available at ftp://axpa.hep.phy.cam.ac.uk/stefano/cavendish_9611.ps or at
http://www.hep.phy.cam.ac.uk/theory/papers
A Reattaching Free Shear Layer in Compressible Turbulent Flow: A Comparison of Numerical and Experimental Results
An investigation of the two-dimensional, free turbulent shear layer reattaching on an inclined surface at Mach 2.92 and at a high Reynolds number is described. The test geometry is specifically designed to isolate the reattachment process of a high-speed separated flow. A numerical solution of the time-dependent, Reynolds-averaged, Navier-Stokes equations for the entire flow field, employing a two-equation eddy viscosity turbulence model, is presented. Detailed comparisons of prediction and experiment are made in the free shear layer, at reattachment, and in the developing boundary layer downstream. These comparisons include mean surface quantities as well as mean and fluctuating flow-field quantities. Although the overall features of this complex flow field are predicted, there are several deficiencies in the numerical solution, particularly in the region downstream of reattachment. Modifications of the turbulence model to correct these deficiencies are discussed
Temporal Model Adaptation for Person Re-Identification
Person re-identification is an open and challenging problem in computer
vision. Majority of the efforts have been spent either to design the best
feature representation or to learn the optimal matching metric. Most approaches
have neglected the problem of adapting the selected features or the learned
model over time. To address such a problem, we propose a temporal model
adaptation scheme with human in the loop. We first introduce a
similarity-dissimilarity learning method which can be trained in an incremental
fashion by means of a stochastic alternating directions methods of multipliers
optimization procedure. Then, to achieve temporal adaptation with limited human
effort, we exploit a graph-based approach to present the user only the most
informative probe-gallery matches that should be used to update the model.
Results on three datasets have shown that our approach performs on par or even
better than state-of-the-art approaches while reducing the manual pairwise
labeling effort by about 80%
Measurement of the electron transmission rate of the gating foil for the TPC of the ILC experiment
We have developed a gating foil for the time projection chamber envisaged as
a central tracker for the international linear collider experiment. It has a
structure similar to the Gas Electron Multiplier (GEM) with a higher optical
aperture ratio and functions as an ion gate without gas amplification. The
transmission rate for electrons was measured in a counting mode for a wide
range of the voltages applied across the foil using an Fe source and a
laser in the absence of a magnetic field. The blocking power of the foil
against positive ions was estimated from the electron transmissions.Comment: 25 pages containing 14 figures and 1 tabl
Discovering Valuable Items from Massive Data
Suppose there is a large collection of items, each with an associated cost
and an inherent utility that is revealed only once we commit to selecting it.
Given a budget on the cumulative cost of the selected items, how can we pick a
subset of maximal value? This task generalizes several important problems such
as multi-arm bandits, active search and the knapsack problem. We present an
algorithm, GP-Select, which utilizes prior knowledge about similarity be- tween
items, expressed as a kernel function. GP-Select uses Gaussian process
prediction to balance exploration (estimating the unknown value of items) and
exploitation (selecting items of high value). We extend GP-Select to be able to
discover sets that simultaneously have high utility and are diverse. Our
preference for diversity can be specified as an arbitrary monotone submodular
function that quantifies the diminishing returns obtained when selecting
similar items. Furthermore, we exploit the structure of the model updates to
achieve an order of magnitude (up to 40X) speedup in our experiments without
resorting to approximations. We provide strong guarantees on the performance of
GP-Select and apply it to three real-world case studies of industrial
relevance: (1) Refreshing a repository of prices in a Global Distribution
System for the travel industry, (2) Identifying diverse, binding-affine
peptides in a vaccine de- sign task and (3) Maximizing clicks in a web-scale
recommender system by recommending items to users
A realistic assessment of methods for extracting gene/protein interactions from free text
Background: The automated extraction of gene and/or protein interactions from the literature is one of the most important targets of biomedical text mining research. In this paper we present a realistic evaluation of gene/protein interaction mining relevant to potential non-specialist users. Hence we have specifically avoided methods that are complex to install or require reimplementation, and we coupled our chosen extraction methods with a state-of-the-art biomedical named entity tagger. Results: Our results show: that performance across different evaluation corpora is extremely variable; that the use of tagged (as opposed to gold standard) gene and protein names has a significant impact on performance, with a drop in F-score of over 20 percentage points being commonplace; and that a simple keyword-based benchmark algorithm when coupled with a named entity tagger outperforms two of the tools most widely used to extract gene/protein interactions. Conclusion: In terms of availability, ease of use and performance, the potential non-specialist user community interested in automatically extracting gene and/or protein interactions from free text is poorly served by current tools and systems. The public release of extraction tools that are easy to install and use, and that achieve state-of-art levels of performance should be treated as a high priority by the biomedical text mining community
Double dynamical regime of confined water
The Van Hove self correlation function of water confined in a silica pore is
calculated from Molecular Dynamics trajectories upon supercooling. At long time
in the relaxation region we found that the behaviour of the real space
time dependent correlators can be decomposed in a very slow, almost frozen,
dynamics due to the bound water close to the substrate and a faster dynamics of
the free water which resides far from the confining surface. For free water we
confirm the evidences of an approach to a crossover mode coupling transition,
previously found in Q space. In the short time region we found that the two
dynamical regimes are overimposed and cannot be distinguished. This shows that
the interplay between the slower and the faster dynamics emerges in going from
early times to the relaxation region, where a layer analysis of the
dynamical properties can be performed.Comment: 6 pages with 9 figures. RevTeX. Accepted for pulbication in J. Phys.
Cond. Mat
Influence of shock wave propagation on dielectric barrier discharge plasma actuator performance
Interest in plasma actuators as active flow control devices is growing rapidly due to their lack of mechanical parts, light weight and high response frequency. Although the flow induced by these actuators has received much attention, the effect that the external flow has on the performance of the actuator itself must also be considered, especially the influence of unsteady high-speed flows which are fast becoming a norm in the operating flight envelopes. The primary objective of this study is to examine the characteristics of a dielectric barrier discharge (DBD) plasma actuator when exposed to an unsteady flow generated by a shock tube. This type of flow, which is often used in different studies, contains a range of flow regimes from sudden pressure and density changes to relatively uniform high-speed flow regions. A small circular shock tube is employed along with the schlieren photography technique to visualize the flow. The voltage and current traces of the plasma actuator are monitored throughout, and using the well-established shock tube theory the change in the actuator characteristics are related to the physical processes which occur inside the shock tube. The results show that not only is the shear layer outside of the shock tube affected by the plasma but the passage of the shock front and high-speed flow behind it also greatly influences the properties of the plasma
- …