6,608 research outputs found
Measurement of the W Mass at LEP2
The mass of the W boson has been measured by the LEP collaborations from the
data recorded during the LEP2 programme at e+ e- centre of mass energies from
161 to 209 GeV, giving the result : mw = 80.450 +/- 0.039 GeV/c^2. This paper
discusses the measurements of the W Mass from direct reconstruction of the
invariant mass of the WW decay products, particular emphasis is placed on the
evaluation of systematic errors. Results on the direct measurement of the W
width are also presented.Comment: Contribution to XXXVIIth Moriond Electroweak Conference, March 2002.
6 pages, 3 figures This version with typos correcte
Chain: A Dynamic Double Auction Framework for Matching Patient Agents
In this paper we present and evaluate a general framework for the design of
truthful auctions for matching agents in a dynamic, two-sided market. A single
commodity, such as a resource or a task, is bought and sold by multiple buyers
and sellers that arrive and depart over time. Our algorithm, Chain, provides
the first framework that allows a truthful dynamic double auction (DA) to be
constructed from a truthful, single-period (i.e. static) double-auction rule.
The pricing and matching method of the Chain construction is unique amongst
dynamic-auction rules that adopt the same building block. We examine
experimentally the allocative efficiency of Chain when instantiated on various
single-period rules, including the canonical McAfee double-auction rule. For a
baseline we also consider non-truthful double auctions populated with
zero-intelligence plus"-style learning agents. Chain-based auctions perform
well in comparison with other schemes, especially as arrival intensity falls
and agent valuations become more volatile
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Specifying and Monitoring Market Mechanisms Using Rights and Obligations
We provide a formal scripting language to capture the semantics of market mechanisms. The language is based on a set of well-defined principles, and is designed to capture an agent’s rights, as derived from property, and an agent’s obligations, as derived from restrictions placed on its actions, either voluntarily or as a consequence of other actions. Rights and obligations are viewed as first-class goods, from which we define fundamental axioms about well-functioning market-oriented worlds. Coupled with the scripting language is a run-time system that is able to monitor and enforce rights and obligations. Our treatment extends to represent a variety of market mechanisms, ranging from simple two-agent single-good exchanges to complicated combinatorial auctions.Engineering and Applied Science
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Learning and Solving Many-Player Games Through a Cluster-Based Representation
In addressing the challenge of exponential scaling with the number of agents we adopt a cluster-based representation to approximately solve asymmetric games of very many players. A cluster groups together agents with a similar “strategic view ” of the game. We learn the clustered approximation from data consisting of strategy profiles and payoffs, which may be obtained from observations of play or access to a simulator. Using our clustering we construct a reduced “twins” game in which each cluster is associated with two players of the reduced game. This allows our representation to be individuallyresponsive because we align the interests of every individual agent with the strategy of its cluster. Our approach provides agents with higher payoffs and lower regret on average than model-free methods as well as previous cluster-based methods, and requires only few observations for learning to be successful. The “twins ” approach is shown to be an important component of providing these low regret approximations.Engineering and Applied Science
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Analysis of Bidding Networks in eBay: Aggregate Preference Identification through Community Detection
Statistical analysis of networks plays a critical role in the context of economics and the social sciences. Here we construct a bidding network to represent the behavior of users of the eBay marketplace. We study the eBay markets for digital cameras and liquid crystal display screens, and employ network analysis to identify aggregate structure in bidder preferences. The network that we construct associates auctions with nodes, and weighted edges between nodes capture the number of bidders competing in a pair of auctions, where said bidders ultimately win in only a single auction. We show that current community detection methods applied to this network allow for the identification of goods that are considered substitutes and complements, and thus the identification of aggregate preference information. In closing we suggest additional opportunities as well as challenges for the analysis of structured data in electronic markets.Engineering and Applied Science
A selected ion flow tube study of the ion-molecule reactions of monochloroethene, trichloroethene and tetrachloroethene
Data for the rate coefficients and product cations of the reactions of a large number of atomic and small molecular cations with monochloroethene, trichloroethene and tetrachloroethene in a selected ion flow tube at 298 K are reported. The recombination energy of the ions range from 6.27 eV (HO) through to 21.56 eV (Ne). Collisional rate coefficients are calculated by modified average dipole orientation theory and compared with experimental values. Thermochemistry and mass balance predict the most feasible neutral products. Together with previously reported results for the three isomers of dichloroethene (J. Phys. Chem. A., 2006, 110, 5760), the fragment ion branching ratios have been compared with those from threshold photoelectron photoion coincidence spectroscopy over the photon energy range 9-22 eV to determine the importance or otherwise of long-range charge transfer. For ions with recombination energy in excess of the ionisation energy of the chloroethene, charge transfer is energetically allowed. The similarity of the branching ratios from the two experiments suggest that long-range charge transfer is dominant. For ions with recombination energy less than the ionisation energy, charge transfer is not allowed; chemical reaction can only occur following formation of an ion-molecule complex, where steric effects are more significant. The products that are now formed and their percentage yield is a complex interplay between the number and position of the chlorine atoms with respect to the C=C bond, where inductive and conjugation effects can be important
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