948 research outputs found
A comparison of CMB- and HLA-based approaches to type I interoperability reference model problems for COTS-based distributed simulation
Commercial-off-the-shelf (COTS) simulation packages (CSPs) are software used by many simulation modellers to build and experiment with models of various systems in domains such as manufacturing, health, logistics and commerce. COTS distributed simulation deals with the interoperation of CSPs and their models. Such interoperability has been classified into six interoperability reference models. As part of an on-going standardisation effort, this paper introduces the COTS Simulation Package Emulator, a proposed benchmark that can be used to investigate Type I interoperability problems in COTS distributed simulation. To demonstrate its use, two approaches to this form of interoperability are discussed, an implementation of the CMB conservative algorithm, an example of a so-called âlightâ approach, and an implementation of the HLA TAR algorithm, an example of a so-called âheavyâ approach. Results from experimentation over four federation topologies are presented and it is shown the HLA approach out performs the CMB approach in almost all cases. The paper concludes that the CSPE benchmark is a valid basis from which the most efficient approach to Type I interoperability problems for COTS distributed simulation can be discovered
The Calan-Hertfordshire Extrasolar Planet Search
The detailed study of the exoplanetary systems HD189733 and HD209458 has
given rise to a wealth of exciting information on the physics of exoplanetary
atmospheres. To further our understanding of the make-up and processes within
these atmospheres we require a larger sample of bright transiting planets. We
have began a project to detect more bright transiting planets in the southern
hemisphere by utilising precision radial-velocity measurements. We have
observed a constrained sample of bright, inactive and metal-rich stars using
the HARPS instrument and here we present the current status of this project,
along with our first discoveries which include a brown dwarf/extreme-Jovian
exoplanet found in the brown dwarf desert region around the star HD191760 and
improved orbits for three other exoplanetary systems HD48265, HD143361 and
HD154672. Finally, we briefly discuss the future of this project and the
current prospects we have for discovering more bright transiting planets.Comment: 4 pages, 2 figures, to appear in the conference proceedings "New
Technologies for Probing the Diversity of Brown Dwarfs and Exoplanets"
Shanghai 200
Demonstration of laser pulse amplification by stimulated Brillouin scattering
The energy transfer by stimulated Brillouin backscatter from a long pump pulse (15 ps) to a short seed pulse (1 ps) has been investigated in a proof-of-principle demonstration experiment. The two pulses were both amplified in different beamlines of a Nd:glass laser system, had a central wavelength of 1054 nm and a spectral bandwidth of 2 nm, and crossed each other in an underdense plasma in a counter-propagating geometry, off-set by 10â. It is shown that the energy transfer and the wavelength of the generated Brillouin peak depend on the plasma density, the intensity of the laser pulses, and the competition between two-plasmon decay and stimulated Raman scatter instabilities. The highest obtained energy transfer from pump to probe pulse is 2.5%, at a plasma density of 0.17ncr, and this energy transfer increases significantly with plasma density. Therefore, our results suggest that much higher efficiencies can be obtained when higher densities (above 0.25ncr) are used
Study of B meson decays to three-body charmless hadronic final states
We report results of a study of charmless B meson decays to three-body KPiPi,
KKPi and KKK final states. Measurements of branching fractions for B decays to
K+0Pi+Pi-, K+K+K-, K0K+K-, KsKsK+ and KsKsKs final states are presented. The
decays B0=>K0K+K-, B+=>KsKsK+ and B0=>KsKsKs are observed for the first time.
We also report evidence for B+=>K+K-Pi+ decay. For the three-body final states
K0K+K-, KsKsPi+, K+K+Pi- and K-Pi+Pi+ 90% confidence level upper limits are
reported. Finally, we discuss the possibility of using the three-body
B0=>KsK+K- decay for CP violation studies. The results are obtained with a 78
fb^-1 data sample collected at the Y(4S) resonance by the Belle detector
operating at the KEKB asymmetric energy e+e- collider.Comment: 15 pages, 6 figures. To be submitted to PR
Measurement of the Spectroscopy of Orbitally Excited B Mesons at LEP
We measure the masses, decay widths and relative production rate of orbitally
excited B mesons using 1.25 million hadronic Z decays recorded by the L3
detector. B-meson candidates are inclusively reconstructed and combined with
charged pions produced at the primary event vertex. An excess of events above
the expected background in the B\pi mass spectrum in the region 5.6-5.8 GeV is
interpreted as resulting from the decay B_u,d^** -> B^(*)\pi, where B_u,d^**
denotes a mixture of l=1 B-meson states containing a u or a d quark. A fit to
the mass spectrum yields the masses and decay widths of the B_1^* and B_2^*
spin states, as well as the branching fraction for the combination of l=1
states. In addition, evidence is presented for the existence of an excited
B-meson state or mixture of states in the region 5.9-6.0 GeV
Measurement of the W+W-gamma Cross Section and Direct Limits on Anomalous Quartic Gauge Boson Couplings at LEP
The process e+e- -> W+W-gamma is analysed using the data collected with the
L3 detector at LEP at a centre-of-mass energy of 188.6GeV, corresponding to an
integrated luminosity of 176.8pb^-1. Based on a sample of 42 selected W+W-
candidates containing an isolated hard photon, the W+W-gamma cross section,
defined within phase-space cuts, is measured to be: sigma_WWgamma = 290 +/- 80
+/- 16 fb, consistent with the Standard Model expectation. Including the
process e+e- -> nu nu gamma gamma, limits are derived on anomalous
contributions to the Standard Model quartic vertices W+W- gamma gamma and W+W-Z
gamma at 95% CL: -0.043 GeV^-2 < a_0/Lambda^2 < 0.043 GeV^-2 0.08 GeV^-2 <
a_c/Lambda^2 < 0.13 GeV^-2 0.41 GeV^-2 < a_n/Lambda^2 < 0.37 GeV^-2
Production of Single W Bosons at \sqrt{s}=189 GeV and Measurement of WWgamma Gauge Couplings
Single W boson production in electron-positron collisions is studied with the
L3 detector at LEP. The data sample collected at a centre-of-mass energy of
\sqrt{s} = 188.7GeV corresponds to an integrated luminosity of 176.4pb^-1.
Events with a single energetic lepton or two acoplanar hadronic jets are
selected. Within phase-space cuts, the total cross-section is measured to be
0.53 +/- 0.12 +/- 0.03 pb, consistent with the Standard Model expectation.
Including our single W boson results obtained at lower \sqrt{s}, the WWgamma
gauge couplings kappa_gamma and lambda_gamma are determined to be kappa_gamma =
0.93 +/- 0.16 +/- 0.09 and lambda_gamma = -0.31 +0.68 -0.19 +/- 0.13
Search for an invisibly decaying Higgs boson in e^+e^- collisions at \sqrt{s} = 183 - 189 GeV
A search for a Higgs boson decaying into invisible particles is performed
using the data collected at LEP by the L3 experiment at centre-of-mass energies
of 183 GeV and 189 GeV. The integrated luminosities are respectively 55.3 pb^-1
and 176.4 pb^-1. The observed candidates are consistent with the expectations
from Standard Model processes. In the hypothesis that the production cross
section of this Higgs boson equals the Standard Model one and the branching
ratio into invisible particles is 100%, a lower mass limit of 89.2 GeV is set
at 95% confidence level
Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in e+e- Interactions at \sqrt{s} = 189 GeV
A search for the lightest neutral scalar and neutral pseudoscalar Higgs
bosons in the Minimal Supersymmetric Standard Model is performed using 176.4
pb^-1 of integrated luminosity collected by L3 at a center-of-mass energy of
189 GeV. No signal is observed, and the data are consistent with the expected
Standard Model background. Lower limits on the masses of the lightest neutral
scalar and pseudoscalar Higgs bosons are given as a function of tan(beta).
Lower mass limits for tan(beta)>1 are set at the 95% confidence level to be m_h
> 77.1 GeV and m_A > 77.1 GeV
Measurement of Bose-Einstein Correlations in e+e- -> W+W- at root(s)=189GeV
We investigate Bose-Einstein correlations (BEC) in W-pair production at
root(s)=189GeV using the L3 detector at LEP. We observe BEC between particles
from a single W decay in good agreement with those from a light-quark Z decay
sample. We investigate their possible existence between particles coming from
different W's. No evidence for such inter-W BEC is found
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