1,321 research outputs found
From an automated flight-test management system to a flight-test engineer's workstation
The capabilities and evolution is described of a flight engineer's workstation (called TEST-PLAN) from an automated flight test management system. The concept and capabilities of the automated flight test management systems are explored and discussed to illustrate the value of advanced system prototyping and evolutionary software development
Signals for Vector Leptoquarks in Hadronic Collisions
We analyze systematically the signatures of vector leptoquarks in hadronic
collisions. We examine their single and pair productions, as well as their
effects on the production of lepton pairs. Our results indicate that a machine
like the CERN Large Hadron Collider (LHC) will be able to unravel the existence
of vector leptoquarks with masses up to the range of -- TeV.Comment: 15 pages and 5 figures (available upon request or through anonymous
ftp), revtex3, IFUSP-P 108
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Nonadiabatic scattering and transport at the spindle cusp
When magnetohydrodynamics is used to describe plasma flow across a separatrix to open field lines, the transport is modeled by a diffusion equation with a sink for particles on the open lines. In that case, it is assumed that plasma is carried to and from the separatrix by diffusive processes. The purpose of this note is to discuss the nonadiabatic processes occurring at a spindle cusp to transfer plasma across a separatrix. After an ion is delivered to the vicinity of the separatrix by diffusion it enters the spindle cusp and will skip back and forth across the separatrix, producing a structured transport not seen with MHD
The use of an automated flight test management system in the development of a rapid-prototyping flight research facility
An automated flight test management system (ATMS) and its use to develop a rapid-prototyping flight research facility for artificial intelligence (AI) based flight systems concepts are described. The ATMS provides a flight test engineer with a set of tools that assist in flight planning and simulation. This system will be capable of controlling an aircraft during the flight test by performing closed-loop guidance functions, range management, and maneuver-quality monitoring. The rapid-prototyping flight research facility is being developed at the Dryden Flight Research Facility of the NASA Ames Research Center (Ames-Dryden) to provide early flight assessment of emerging AI technology. The facility is being developed as one element of the aircraft automation program which focuses on the qualification and validation of embedded real-time AI-based systems
Theory of pixel lensing towards M31 I: the density contribution and mass of MACHOs
POINT-AGAPE is an Anglo-French collaboration which is employing the Isaac
Newton Telescope (INT) to conduct a pixel-lensing survey towards M31. In this
paper we investigate what we can learn from pixel-lensing observables about the
MACHO mass and fractional contribution in M31 and the Galaxy for the case of
spherically-symmetric near-isothermal haloes. We employ detailed pixel-lensing
simulations which include many of the factors which affect the observables. For
a maximum MACHO halo we predict an event rate in V of up to 100 per season for
M31 and 40 per season for the Galaxy. However, the Einstein radius crossing
time is generally not measurable and the observed full-width half-maximum
duration provides only a weak tracer of lens mass. Nonetheless, we find that
the near-far asymmetry in the spatial distribution of M31 MACHOs provides
significant information on their mass and density contribution. We present a
likelihood estimator for measuring the fractional contribution and mass of both
M31 and Galaxy MACHOs which permits an unbiased determination to be made of
MACHO parameters, even from data-sets strongly contaminated by variable stars.
If M31 does not have a significant population of MACHOs in the mass range
0.001-1 Solar masses strong limits will result from the first season of INT
observations. Simulations based on currently favoured density and mass values
indicate that, after three seasons, the M31 MACHO parameters should be
constrained to within a factor four uncertainty in halo fraction and an order
of magnitude uncertainty in mass (90% confidence). Interesting constraints on
Galaxy MACHOs may also be possible. For a campaign lasting ten years,
comparable to the lifetime of current LMC surveys, reliable estimates of MACHO
parameters in both galaxies should be possible. (Abridged)Comment: 21 pages, 14 figures. Submitted to MNRA
Dark Matter from Baryon Asymmetry
The measured densities of dark and baryonic matter are surprisingly close to
each other, even though the baryon asymmetry and the dark matter are usually
explained by unrelated mechanisms. We consider a scenario where the dark matter
S is produced non-thermally from the decay of a messenger particle X, which
carries the baryon number and compensates for the baryon asymmetry in the
Universe, thereby establishing a connection between the baryonic and dark
matter densities. We propose a simple model to realize this scenario, adding
only a light singlet fermion S and a colored particle X which has a mass in the
O(TeV) range and a lifetime to appear long-lived in collider detector.
Therefore in hadron colliders the signal is similar to that of a stable or
long-lived gluino in supersymmetric models.Comment: 12 pages; v2: bounds on the mass of the messenger particle are
relaxed; conclusions unchanged. additional minor modification
Production of Pairs of Sleptoquarks in Hadron Colliders
We calculate the cross section for the production of pairs of scalar
leptoquarks (sleptoquarks) in a supersymmetric model, at hadron
colliders. We estimate higher order corrections by including terms
induced by soft-gluon corrections. Discovery bounds on the sleptoquark mass are
estimated at collider energies of 1.8, 2, and 4 TeV (Tevatron), and 16 TeV
(LHC).Comment: 8 pages, REVTEX, (1 fig. available on request),
LAVAL-PHY-94-13/McGILL-94-26/SPhT-94-07
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