65,878 research outputs found
Why the xE distribution triggered by a leading particle does not measure the fragmentation function but does measure the ratio of the transverse momenta of the away-side jet to the trigger-side jet
Hard-scattering of point-like constituents (or partons) in p-p collisions was
discovered at the CERN-ISR in 1972 by measurements utilizing inclusive single
or pairs of hadrons with large transverse momentum (). It was generally
assumed, following Feynman, Field and Fox, as shown by data from the CERN-ISR
experiments, that the distribution of away side hadrons from a single
particle trigger [with ], corrected for of fragmentation would
be the same as that from a jet-trigger and follow the same fragmentation
function as observed in or DIS. PHENIX attempted to measure the
fragmentation function from the away side
distribution of charged particles triggered by a in p-p collisions at
RHIC and showed by explicit calculation that the distribution is actually
quite insensitive to the fragmentation function. Illustrations of the original
arguments and ISR results will be presented. Then the lack of sensitivity to
the fragmentation function will be explained, and an analytic formula for the
distribution given, in terms of incomplete Gamma functions, for the case
where the fragmentation function is exponential. The away-side distribution in
this formulation has the nice property that it both exhibits scaling and
is directly sensitive to the ratio of the away jet to that of
the trigger jet, , and thus can be used, for example, to measure
the relative energy loss of the two jets from a hard-scattering which escape
from the medium in A+A collisions. Comparisons of the analytical formula to
RHIC measurements will be presented, including data from STAR and PHENIX,
leading to some interesting conclusions.Comment: 6 pages, 5 figures, Proceedings of Poster Session, 19th International
Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter
2006), November 14-20, 2006, Shanghai, P. R. Chin
Design concepts for large reflector antenna structures
Practical approaches for establishing large, precise antenna reflectors in space are described. Reflector surfaces consisting of either solid panels or knitted mesh are considered. The approach using a deep articulated truss structure to support a mesh reflector is selected for detailed investigations. A new sequential deployment concept for the tetrahedral truss is explained. Good joint design is discussed, and examples are described both analytically and by means of demonstration models. The influence of curvature on the design and its vibration characteristics are investigated
Efficient structures for geosynchronous spacecraft solar arrays. Phase 1, 2 and 3
Structural concepts for deploying and supporting lightweight solar-array blankets for geosynchronous electrical power are evaluated. It is recommended that the STACBEAM solar-array system should be the object of further study and detailed evaluation. The STACBEAM system provides high stiffness at low mass, and with the use of a low mass deployment mechanism, full structural properties can be maintained throughout deployment. The stowed volume of the STACBEAM is acceptably small, and its linear deployment characteristic allows periodic attachments to the solar-array blanket to be established in the stowed configuration and maintained during deployment
Tachyon condensation and off-shell gravity/gauge duality
We investigate quasilocal tachyon condensation by using gravity/gauge
duality. In order to cure the IR divergence due to a tachyon, we introduce two
regularization schemes: AdS space and a d=10 Schwarzschild black hole in a
cavity. These provide stable canonical ensembles and thus are good candidates
for the endpoint of tachyon condensation. Introducing the Cardy-Verlinde
formula, we establish the on-shell gravity/gauge duality. We propose that the
stringy geometry resulting from the off-shell tachyon dynamics matches onto the
off-shell AdS black hole, where "off-shell" means non-equilibrium
configuration. The instability induced by condensation of a tachyon behaves
like an off-shell black hole and evolves toward a large stable black hole. The
off-shell free energy and its derivative (-function) are used to show
the off-shell gravity/gauge duality for the process of tachyon condensation.
Further, d=10 Schwarzschild black hole in a cavity is considered for the
Hagedorn transition as a possible explanation of the tachyon condensation.Comment: 28 pages, 13 eps figures, version to appear in IJMP
A system design for human factors studies of speech-enabled Web browsing
This paper describes the design of a system which will subsequently be used as the basis of a range of empirical studies aimed at discovering how best to harness speech recognition capabilities in multimodal multimedia computing. Initial work focuses on speech-enabled browsing of the World Wide Web, which was never designed for such use. System design is complete, and is being evaluated via usability testing
Development of an integrated data base for land use and water quality planning
To help understand the role played by different land resources in water quality management a computer based data system was created. The Land Resource Information System (LRIS) allows data to be readily retrieved or statistically analyzed for a variety of purposes. It is specifically formatted to perform coordination of water quality data with logy, etc. New understanding of the region gained through the use of LRIS has gone well beyond the initial purpose of assessing water quality conditions. The land use and natural features information has provided a well defined starting point for a systematic evaluation of proposed land uses, transportation, housing, and other public investments. It has laid the foundation for a comprehensive and integrated approach to many different planning and investment programs presently underway
Reported Trip Costs, Gross Revenues, and Net Returns for U.S. Atlantic Pelagic Longline Vessels
Logbook set and trip summary data (containing catch and cost information, respectively) collected by NOAA’s National Marine Fisheries Service (NMFS) were analyzed for U.S. pelagic longline vessels that participated in Atlantic fisheries in 1996. These data were augmented with vessel information from the U.S. Coast Guard. Mean fish weights and ex-vessel prices from NMFS observers and licensed seafood dealers, respectively, were used to estimate gross revenues. Comparisons revealed that net returns varied substantially by vessel size and fishing behavior (i.e. sets per trip, fishing location, season, and swordfish targeting). While the calculated economic effects of proposed regulations will depend on the descriptive statistic chosen for analysis, which itself depends on the type of analysis being conducted, results show that considering heterogeneity within this fleet can have a significant effect on predicted economic consequences
Economic profile of Florida's marine life industry
The marine life industry in Florida is defined as the harvest of live marine specimens (fish and
invertebrate species including plants, live rock and sand, and small “critters”) for commercial use,
primarily aquariums. This paper summarizes data collected on the industry since 1990, including
total landings, revenues, and trends over time. Regional analysis shows where the primary collecting
areas are located in Florida. Seasonal analysis shows when the majority of landings occur within the
year. Statistics on the number of participants by type (i.e., collector versus wholesaler) provide
insight into the size of the industry. Trends are evaluated in terms of changes across the 9-year
period from 1990 to 1998. In general, the number of licensed collectors has increased substantially,
landings of fish and animal invertebrates peaked in 1994, angelfish dominated the fish landings, live
rock dominated the invertebrate landings, and the average landings per trip have remained relatively
constant. (67pp.
1999 US tropical fish wholesaler survey: results and implications
A survey of marine life wholesalers was initiated in 1999 as a first step towards understanding the
nature of Florida’s marine life industry, the demand for Florida products, and the need for changes in
the way the industry is regulated. Florida firms deal primarily in marine species and collect much of
their own product. Wholesalers outside of Florida handle more freshwater species and purchase most
of their inventory, the majority from overseas suppliers. Dealers predict that the average firm size
will continue to grow as the industry consolidates. Niche markets for eco-friendly product will gain
momentum. In Florida, marketing strategies should point to the high quality of Florida species with
emphasis on the growing popularity of invertebrates. Wholesalers should look to provide buyers of
Florida product with more consistent quantities throughout the year. Resource managers will be
challenged to find ways to protect over-harvested species without interfering with the collection of
abundant species while considering the effect of new regulations. (42pp.
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